xref: /openbmc/linux/drivers/tty/n_gsm.c (revision 2cf1c348)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * n_gsm.c GSM 0710 tty multiplexor
4  * Copyright (c) 2009/10 Intel Corporation
5  *
6  *	* THIS IS A DEVELOPMENT SNAPSHOT IT IS NOT A FINAL RELEASE *
7  *
8  * TO DO:
9  *	Mostly done:	ioctls for setting modes/timing
10  *	Partly done:	hooks so you can pull off frames to non tty devs
11  *	Restart DLCI 0 when it closes ?
12  *	Improve the tx engine
13  *	Resolve tx side locking by adding a queue_head and routing
14  *		all control traffic via it
15  *	General tidy/document
16  *	Review the locking/move to refcounts more (mux now moved to an
17  *		alloc/free model ready)
18  *	Use newest tty open/close port helpers and install hooks
19  *	What to do about power functions ?
20  *	Termios setting and negotiation
21  *	Do we need a 'which mux are you' ioctl to correlate mux and tty sets
22  *
23  */
24 
25 #include <linux/types.h>
26 #include <linux/major.h>
27 #include <linux/errno.h>
28 #include <linux/signal.h>
29 #include <linux/fcntl.h>
30 #include <linux/sched/signal.h>
31 #include <linux/interrupt.h>
32 #include <linux/tty.h>
33 #include <linux/ctype.h>
34 #include <linux/mm.h>
35 #include <linux/string.h>
36 #include <linux/slab.h>
37 #include <linux/poll.h>
38 #include <linux/bitops.h>
39 #include <linux/file.h>
40 #include <linux/uaccess.h>
41 #include <linux/module.h>
42 #include <linux/timer.h>
43 #include <linux/tty_flip.h>
44 #include <linux/tty_driver.h>
45 #include <linux/serial.h>
46 #include <linux/kfifo.h>
47 #include <linux/skbuff.h>
48 #include <net/arp.h>
49 #include <linux/ip.h>
50 #include <linux/netdevice.h>
51 #include <linux/etherdevice.h>
52 #include <linux/gsmmux.h>
53 #include "tty.h"
54 
55 static int debug;
56 module_param(debug, int, 0600);
57 
58 /* Defaults: these are from the specification */
59 
60 #define T1	10		/* 100mS */
61 #define T2	34		/* 333mS */
62 #define N2	3		/* Retry 3 times */
63 
64 /* Use long timers for testing at low speed with debug on */
65 #ifdef DEBUG_TIMING
66 #define T1	100
67 #define T2	200
68 #endif
69 
70 /*
71  * Semi-arbitrary buffer size limits. 0710 is normally run with 32-64 byte
72  * limits so this is plenty
73  */
74 #define MAX_MRU 1500
75 #define MAX_MTU 1500
76 #define	GSM_NET_TX_TIMEOUT (HZ*10)
77 
78 /*
79  *	struct gsm_mux_net	-	network interface
80  *
81  *	Created when net interface is initialized.
82  */
83 struct gsm_mux_net {
84 	struct kref ref;
85 	struct gsm_dlci *dlci;
86 };
87 
88 /*
89  *	Each block of data we have queued to go out is in the form of
90  *	a gsm_msg which holds everything we need in a link layer independent
91  *	format
92  */
93 
94 struct gsm_msg {
95 	struct list_head list;
96 	u8 addr;		/* DLCI address + flags */
97 	u8 ctrl;		/* Control byte + flags */
98 	unsigned int len;	/* Length of data block (can be zero) */
99 	unsigned char *data;	/* Points into buffer but not at the start */
100 	unsigned char buffer[];
101 };
102 
103 enum gsm_dlci_state {
104 	DLCI_CLOSED,
105 	DLCI_OPENING,		/* Sending SABM not seen UA */
106 	DLCI_OPEN,		/* SABM/UA complete */
107 	DLCI_CLOSING,		/* Sending DISC not seen UA/DM */
108 };
109 
110 enum gsm_dlci_mode {
111 	DLCI_MODE_ABM,		/* Normal Asynchronous Balanced Mode */
112 	DLCI_MODE_ADM,		/* Asynchronous Disconnected Mode */
113 };
114 
115 /*
116  *	Each active data link has a gsm_dlci structure associated which ties
117  *	the link layer to an optional tty (if the tty side is open). To avoid
118  *	complexity right now these are only ever freed up when the mux is
119  *	shut down.
120  *
121  *	At the moment we don't free DLCI objects until the mux is torn down
122  *	this avoid object life time issues but might be worth review later.
123  */
124 
125 struct gsm_dlci {
126 	struct gsm_mux *gsm;
127 	int addr;
128 	enum gsm_dlci_state state;
129 	struct mutex mutex;
130 
131 	/* Link layer */
132 	enum gsm_dlci_mode mode;
133 	spinlock_t lock;	/* Protects the internal state */
134 	struct timer_list t1;	/* Retransmit timer for SABM and UA */
135 	int retries;
136 	/* Uplink tty if active */
137 	struct tty_port port;	/* The tty bound to this DLCI if there is one */
138 	struct kfifo fifo;	/* Queue fifo for the DLCI */
139 	int adaption;		/* Adaption layer in use */
140 	int prev_adaption;
141 	u32 modem_rx;		/* Our incoming virtual modem lines */
142 	u32 modem_tx;		/* Our outgoing modem lines */
143 	bool dead;		/* Refuse re-open */
144 	/* Flow control */
145 	bool throttled;		/* Private copy of throttle state */
146 	bool constipated;	/* Throttle status for outgoing */
147 	/* Packetised I/O */
148 	struct sk_buff *skb;	/* Frame being sent */
149 	struct sk_buff_head skb_list;	/* Queued frames */
150 	/* Data handling callback */
151 	void (*data)(struct gsm_dlci *dlci, const u8 *data, int len);
152 	void (*prev_data)(struct gsm_dlci *dlci, const u8 *data, int len);
153 	struct net_device *net; /* network interface, if created */
154 };
155 
156 /* DLCI 0, 62/63 are special or reserved see gsmtty_open */
157 
158 #define NUM_DLCI		64
159 
160 /*
161  *	DLCI 0 is used to pass control blocks out of band of the data
162  *	flow (and with a higher link priority). One command can be outstanding
163  *	at a time and we use this structure to manage them. They are created
164  *	and destroyed by the user context, and updated by the receive paths
165  *	and timers
166  */
167 
168 struct gsm_control {
169 	u8 cmd;		/* Command we are issuing */
170 	u8 *data;	/* Data for the command in case we retransmit */
171 	int len;	/* Length of block for retransmission */
172 	int done;	/* Done flag */
173 	int error;	/* Error if any */
174 };
175 
176 enum gsm_mux_state {
177 	GSM_SEARCH,
178 	GSM_START,
179 	GSM_ADDRESS,
180 	GSM_CONTROL,
181 	GSM_LEN,
182 	GSM_DATA,
183 	GSM_FCS,
184 	GSM_OVERRUN,
185 	GSM_LEN0,
186 	GSM_LEN1,
187 	GSM_SSOF,
188 };
189 
190 /*
191  *	Each GSM mux we have is represented by this structure. If we are
192  *	operating as an ldisc then we use this structure as our ldisc
193  *	state. We need to sort out lifetimes and locking with respect
194  *	to the gsm mux array. For now we don't free DLCI objects that
195  *	have been instantiated until the mux itself is terminated.
196  *
197  *	To consider further: tty open versus mux shutdown.
198  */
199 
200 struct gsm_mux {
201 	struct tty_struct *tty;		/* The tty our ldisc is bound to */
202 	spinlock_t lock;
203 	struct mutex mutex;
204 	unsigned int num;
205 	struct kref ref;
206 
207 	/* Events on the GSM channel */
208 	wait_queue_head_t event;
209 
210 	/* Bits for GSM mode decoding */
211 
212 	/* Framing Layer */
213 	unsigned char *buf;
214 	enum gsm_mux_state state;
215 	unsigned int len;
216 	unsigned int address;
217 	unsigned int count;
218 	bool escape;
219 	int encoding;
220 	u8 control;
221 	u8 fcs;
222 	u8 received_fcs;
223 	u8 *txframe;			/* TX framing buffer */
224 
225 	/* Method for the receiver side */
226 	void (*receive)(struct gsm_mux *gsm, u8 ch);
227 
228 	/* Link Layer */
229 	unsigned int mru;
230 	unsigned int mtu;
231 	int initiator;			/* Did we initiate connection */
232 	bool dead;			/* Has the mux been shut down */
233 	struct gsm_dlci *dlci[NUM_DLCI];
234 	bool constipated;		/* Asked by remote to shut up */
235 
236 	spinlock_t tx_lock;
237 	unsigned int tx_bytes;		/* TX data outstanding */
238 #define TX_THRESH_HI		8192
239 #define TX_THRESH_LO		2048
240 	struct list_head tx_list;	/* Pending data packets */
241 
242 	/* Control messages */
243 	struct timer_list t2_timer;	/* Retransmit timer for commands */
244 	int cretries;			/* Command retry counter */
245 	struct gsm_control *pending_cmd;/* Our current pending command */
246 	spinlock_t control_lock;	/* Protects the pending command */
247 
248 	/* Configuration */
249 	int adaption;		/* 1 or 2 supported */
250 	u8 ftype;		/* UI or UIH */
251 	int t1, t2;		/* Timers in 1/100th of a sec */
252 	int n2;			/* Retry count */
253 
254 	/* Statistics (not currently exposed) */
255 	unsigned long bad_fcs;
256 	unsigned long malformed;
257 	unsigned long io_error;
258 	unsigned long bad_size;
259 	unsigned long unsupported;
260 };
261 
262 
263 /*
264  *	Mux objects - needed so that we can translate a tty index into the
265  *	relevant mux and DLCI.
266  */
267 
268 #define MAX_MUX		4			/* 256 minors */
269 static struct gsm_mux *gsm_mux[MAX_MUX];	/* GSM muxes */
270 static DEFINE_SPINLOCK(gsm_mux_lock);
271 
272 static struct tty_driver *gsm_tty_driver;
273 
274 /* Save dlci open address */
275 static int addr_open[256] = { 0 };
276 /* Save dlci open count */
277 static int addr_cnt;
278 /*
279  *	This section of the driver logic implements the GSM encodings
280  *	both the basic and the 'advanced'. Reliable transport is not
281  *	supported.
282  */
283 
284 #define CR			0x02
285 #define EA			0x01
286 #define	PF			0x10
287 
288 /* I is special: the rest are ..*/
289 #define RR			0x01
290 #define UI			0x03
291 #define RNR			0x05
292 #define REJ			0x09
293 #define DM			0x0F
294 #define SABM			0x2F
295 #define DISC			0x43
296 #define UA			0x63
297 #define	UIH			0xEF
298 
299 /* Channel commands */
300 #define CMD_NSC			0x09
301 #define CMD_TEST		0x11
302 #define CMD_PSC			0x21
303 #define CMD_RLS			0x29
304 #define CMD_FCOFF		0x31
305 #define CMD_PN			0x41
306 #define CMD_RPN			0x49
307 #define CMD_FCON		0x51
308 #define CMD_CLD			0x61
309 #define CMD_SNC			0x69
310 #define CMD_MSC			0x71
311 
312 /* Virtual modem bits */
313 #define MDM_FC			0x01
314 #define MDM_RTC			0x02
315 #define MDM_RTR			0x04
316 #define MDM_IC			0x20
317 #define MDM_DV			0x40
318 
319 #define GSM0_SOF		0xF9
320 #define GSM1_SOF		0x7E
321 #define GSM1_ESCAPE		0x7D
322 #define GSM1_ESCAPE_BITS	0x20
323 #define XON			0x11
324 #define XOFF			0x13
325 
326 static const struct tty_port_operations gsm_port_ops;
327 
328 /*
329  *	CRC table for GSM 0710
330  */
331 
332 static const u8 gsm_fcs8[256] = {
333 	0x00, 0x91, 0xE3, 0x72, 0x07, 0x96, 0xE4, 0x75,
334 	0x0E, 0x9F, 0xED, 0x7C, 0x09, 0x98, 0xEA, 0x7B,
335 	0x1C, 0x8D, 0xFF, 0x6E, 0x1B, 0x8A, 0xF8, 0x69,
336 	0x12, 0x83, 0xF1, 0x60, 0x15, 0x84, 0xF6, 0x67,
337 	0x38, 0xA9, 0xDB, 0x4A, 0x3F, 0xAE, 0xDC, 0x4D,
338 	0x36, 0xA7, 0xD5, 0x44, 0x31, 0xA0, 0xD2, 0x43,
339 	0x24, 0xB5, 0xC7, 0x56, 0x23, 0xB2, 0xC0, 0x51,
340 	0x2A, 0xBB, 0xC9, 0x58, 0x2D, 0xBC, 0xCE, 0x5F,
341 	0x70, 0xE1, 0x93, 0x02, 0x77, 0xE6, 0x94, 0x05,
342 	0x7E, 0xEF, 0x9D, 0x0C, 0x79, 0xE8, 0x9A, 0x0B,
343 	0x6C, 0xFD, 0x8F, 0x1E, 0x6B, 0xFA, 0x88, 0x19,
344 	0x62, 0xF3, 0x81, 0x10, 0x65, 0xF4, 0x86, 0x17,
345 	0x48, 0xD9, 0xAB, 0x3A, 0x4F, 0xDE, 0xAC, 0x3D,
346 	0x46, 0xD7, 0xA5, 0x34, 0x41, 0xD0, 0xA2, 0x33,
347 	0x54, 0xC5, 0xB7, 0x26, 0x53, 0xC2, 0xB0, 0x21,
348 	0x5A, 0xCB, 0xB9, 0x28, 0x5D, 0xCC, 0xBE, 0x2F,
349 	0xE0, 0x71, 0x03, 0x92, 0xE7, 0x76, 0x04, 0x95,
350 	0xEE, 0x7F, 0x0D, 0x9C, 0xE9, 0x78, 0x0A, 0x9B,
351 	0xFC, 0x6D, 0x1F, 0x8E, 0xFB, 0x6A, 0x18, 0x89,
352 	0xF2, 0x63, 0x11, 0x80, 0xF5, 0x64, 0x16, 0x87,
353 	0xD8, 0x49, 0x3B, 0xAA, 0xDF, 0x4E, 0x3C, 0xAD,
354 	0xD6, 0x47, 0x35, 0xA4, 0xD1, 0x40, 0x32, 0xA3,
355 	0xC4, 0x55, 0x27, 0xB6, 0xC3, 0x52, 0x20, 0xB1,
356 	0xCA, 0x5B, 0x29, 0xB8, 0xCD, 0x5C, 0x2E, 0xBF,
357 	0x90, 0x01, 0x73, 0xE2, 0x97, 0x06, 0x74, 0xE5,
358 	0x9E, 0x0F, 0x7D, 0xEC, 0x99, 0x08, 0x7A, 0xEB,
359 	0x8C, 0x1D, 0x6F, 0xFE, 0x8B, 0x1A, 0x68, 0xF9,
360 	0x82, 0x13, 0x61, 0xF0, 0x85, 0x14, 0x66, 0xF7,
361 	0xA8, 0x39, 0x4B, 0xDA, 0xAF, 0x3E, 0x4C, 0xDD,
362 	0xA6, 0x37, 0x45, 0xD4, 0xA1, 0x30, 0x42, 0xD3,
363 	0xB4, 0x25, 0x57, 0xC6, 0xB3, 0x22, 0x50, 0xC1,
364 	0xBA, 0x2B, 0x59, 0xC8, 0xBD, 0x2C, 0x5E, 0xCF
365 };
366 
367 #define INIT_FCS	0xFF
368 #define GOOD_FCS	0xCF
369 
370 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len);
371 
372 /**
373  *	gsm_fcs_add	-	update FCS
374  *	@fcs: Current FCS
375  *	@c: Next data
376  *
377  *	Update the FCS to include c. Uses the algorithm in the specification
378  *	notes.
379  */
380 
381 static inline u8 gsm_fcs_add(u8 fcs, u8 c)
382 {
383 	return gsm_fcs8[fcs ^ c];
384 }
385 
386 /**
387  *	gsm_fcs_add_block	-	update FCS for a block
388  *	@fcs: Current FCS
389  *	@c: buffer of data
390  *	@len: length of buffer
391  *
392  *	Update the FCS to include c. Uses the algorithm in the specification
393  *	notes.
394  */
395 
396 static inline u8 gsm_fcs_add_block(u8 fcs, u8 *c, int len)
397 {
398 	while (len--)
399 		fcs = gsm_fcs8[fcs ^ *c++];
400 	return fcs;
401 }
402 
403 /**
404  *	gsm_read_ea		-	read a byte into an EA
405  *	@val: variable holding value
406  *	@c: byte going into the EA
407  *
408  *	Processes one byte of an EA. Updates the passed variable
409  *	and returns 1 if the EA is now completely read
410  */
411 
412 static int gsm_read_ea(unsigned int *val, u8 c)
413 {
414 	/* Add the next 7 bits into the value */
415 	*val <<= 7;
416 	*val |= c >> 1;
417 	/* Was this the last byte of the EA 1 = yes*/
418 	return c & EA;
419 }
420 
421 /**
422  *	gsm_encode_modem	-	encode modem data bits
423  *	@dlci: DLCI to encode from
424  *
425  *	Returns the correct GSM encoded modem status bits (6 bit field) for
426  *	the current status of the DLCI and attached tty object
427  */
428 
429 static u8 gsm_encode_modem(const struct gsm_dlci *dlci)
430 {
431 	u8 modembits = 0;
432 	/* FC is true flow control not modem bits */
433 	if (dlci->throttled)
434 		modembits |= MDM_FC;
435 	if (dlci->modem_tx & TIOCM_DTR)
436 		modembits |= MDM_RTC;
437 	if (dlci->modem_tx & TIOCM_RTS)
438 		modembits |= MDM_RTR;
439 	if (dlci->modem_tx & TIOCM_RI)
440 		modembits |= MDM_IC;
441 	if (dlci->modem_tx & TIOCM_CD)
442 		modembits |= MDM_DV;
443 	return modembits;
444 }
445 
446 /**
447  *	gsm_print_packet	-	display a frame for debug
448  *	@hdr: header to print before decode
449  *	@addr: address EA from the frame
450  *	@cr: C/R bit from the frame
451  *	@control: control including PF bit
452  *	@data: following data bytes
453  *	@dlen: length of data
454  *
455  *	Displays a packet in human readable format for debugging purposes. The
456  *	style is based on amateur radio LAP-B dump display.
457  */
458 
459 static void gsm_print_packet(const char *hdr, int addr, int cr,
460 					u8 control, const u8 *data, int dlen)
461 {
462 	if (!(debug & 1))
463 		return;
464 
465 	pr_info("%s %d) %c: ", hdr, addr, "RC"[cr]);
466 
467 	switch (control & ~PF) {
468 	case SABM:
469 		pr_cont("SABM");
470 		break;
471 	case UA:
472 		pr_cont("UA");
473 		break;
474 	case DISC:
475 		pr_cont("DISC");
476 		break;
477 	case DM:
478 		pr_cont("DM");
479 		break;
480 	case UI:
481 		pr_cont("UI");
482 		break;
483 	case UIH:
484 		pr_cont("UIH");
485 		break;
486 	default:
487 		if (!(control & 0x01)) {
488 			pr_cont("I N(S)%d N(R)%d",
489 				(control & 0x0E) >> 1, (control & 0xE0) >> 5);
490 		} else switch (control & 0x0F) {
491 			case RR:
492 				pr_cont("RR(%d)", (control & 0xE0) >> 5);
493 				break;
494 			case RNR:
495 				pr_cont("RNR(%d)", (control & 0xE0) >> 5);
496 				break;
497 			case REJ:
498 				pr_cont("REJ(%d)", (control & 0xE0) >> 5);
499 				break;
500 			default:
501 				pr_cont("[%02X]", control);
502 		}
503 	}
504 
505 	if (control & PF)
506 		pr_cont("(P)");
507 	else
508 		pr_cont("(F)");
509 
510 	print_hex_dump_bytes("", DUMP_PREFIX_NONE, data, dlen);
511 }
512 
513 
514 /*
515  *	Link level transmission side
516  */
517 
518 /**
519  *	gsm_stuff_frame	-	bytestuff a packet
520  *	@input: input buffer
521  *	@output: output buffer
522  *	@len: length of input
523  *
524  *	Expand a buffer by bytestuffing it. The worst case size change
525  *	is doubling and the caller is responsible for handing out
526  *	suitable sized buffers.
527  */
528 
529 static int gsm_stuff_frame(const u8 *input, u8 *output, int len)
530 {
531 	int olen = 0;
532 	while (len--) {
533 		if (*input == GSM1_SOF || *input == GSM1_ESCAPE
534 		    || *input == XON || *input == XOFF) {
535 			*output++ = GSM1_ESCAPE;
536 			*output++ = *input++ ^ GSM1_ESCAPE_BITS;
537 			olen++;
538 		} else
539 			*output++ = *input++;
540 		olen++;
541 	}
542 	return olen;
543 }
544 
545 /**
546  *	gsm_send	-	send a control frame
547  *	@gsm: our GSM mux
548  *	@addr: address for control frame
549  *	@cr: command/response bit
550  *	@control:  control byte including PF bit
551  *
552  *	Format up and transmit a control frame. These do not go via the
553  *	queueing logic as they should be transmitted ahead of data when
554  *	they are needed.
555  *
556  *	FIXME: Lock versus data TX path
557  */
558 
559 static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
560 {
561 	int len;
562 	u8 cbuf[10];
563 	u8 ibuf[3];
564 
565 	switch (gsm->encoding) {
566 	case 0:
567 		cbuf[0] = GSM0_SOF;
568 		cbuf[1] = (addr << 2) | (cr << 1) | EA;
569 		cbuf[2] = control;
570 		cbuf[3] = EA;	/* Length of data = 0 */
571 		cbuf[4] = 0xFF - gsm_fcs_add_block(INIT_FCS, cbuf + 1, 3);
572 		cbuf[5] = GSM0_SOF;
573 		len = 6;
574 		break;
575 	case 1:
576 	case 2:
577 		/* Control frame + packing (but not frame stuffing) in mode 1 */
578 		ibuf[0] = (addr << 2) | (cr << 1) | EA;
579 		ibuf[1] = control;
580 		ibuf[2] = 0xFF - gsm_fcs_add_block(INIT_FCS, ibuf, 2);
581 		/* Stuffing may double the size worst case */
582 		len = gsm_stuff_frame(ibuf, cbuf + 1, 3);
583 		/* Now add the SOF markers */
584 		cbuf[0] = GSM1_SOF;
585 		cbuf[len + 1] = GSM1_SOF;
586 		/* FIXME: we can omit the lead one in many cases */
587 		len += 2;
588 		break;
589 	default:
590 		WARN_ON(1);
591 		return;
592 	}
593 	gsmld_output(gsm, cbuf, len);
594 	if (!gsm->initiator) {
595 		cr = cr & gsm->initiator;
596 		control = control & ~PF;
597 	}
598 	gsm_print_packet("-->", addr, cr, control, NULL, 0);
599 }
600 
601 /**
602  *	gsm_response	-	send a control response
603  *	@gsm: our GSM mux
604  *	@addr: address for control frame
605  *	@control:  control byte including PF bit
606  *
607  *	Format up and transmit a link level response frame.
608  */
609 
610 static inline void gsm_response(struct gsm_mux *gsm, int addr, int control)
611 {
612 	gsm_send(gsm, addr, 1, control);
613 }
614 
615 /**
616  *	gsm_command	-	send a control command
617  *	@gsm: our GSM mux
618  *	@addr: address for control frame
619  *	@control:  control byte including PF bit
620  *
621  *	Format up and transmit a link level command frame.
622  */
623 
624 static inline void gsm_command(struct gsm_mux *gsm, int addr, int control)
625 {
626 	gsm_send(gsm, addr, 1, control);
627 }
628 
629 /* Data transmission */
630 
631 #define HDR_LEN		6	/* ADDR CTRL [LEN.2] DATA FCS */
632 
633 /**
634  *	gsm_data_alloc		-	allocate data frame
635  *	@gsm: GSM mux
636  *	@addr: DLCI address
637  *	@len: length excluding header and FCS
638  *	@ctrl: control byte
639  *
640  *	Allocate a new data buffer for sending frames with data. Space is left
641  *	at the front for header bytes but that is treated as an implementation
642  *	detail and not for the high level code to use
643  */
644 
645 static struct gsm_msg *gsm_data_alloc(struct gsm_mux *gsm, u8 addr, int len,
646 								u8 ctrl)
647 {
648 	struct gsm_msg *m = kmalloc(sizeof(struct gsm_msg) + len + HDR_LEN,
649 								GFP_ATOMIC);
650 	if (m == NULL)
651 		return NULL;
652 	m->data = m->buffer + HDR_LEN - 1;	/* Allow for FCS */
653 	m->len = len;
654 	m->addr = addr;
655 	m->ctrl = ctrl;
656 	INIT_LIST_HEAD(&m->list);
657 	return m;
658 }
659 
660 /**
661  *	gsm_data_kick		-	poke the queue
662  *	@gsm: GSM Mux
663  *	@dlci: DLCI sending the data
664  *
665  *	The tty device has called us to indicate that room has appeared in
666  *	the transmit queue. Ram more data into the pipe if we have any
667  *	If we have been flow-stopped by a CMD_FCOFF, then we can only
668  *	send messages on DLCI0 until CMD_FCON
669  *
670  *	FIXME: lock against link layer control transmissions
671  */
672 
673 static void gsm_data_kick(struct gsm_mux *gsm, struct gsm_dlci *dlci)
674 {
675 	struct gsm_msg *msg, *nmsg;
676 	int len;
677 
678 	list_for_each_entry_safe(msg, nmsg, &gsm->tx_list, list) {
679 		if (gsm->constipated && msg->addr)
680 			continue;
681 		if (gsm->encoding != 0) {
682 			gsm->txframe[0] = GSM1_SOF;
683 			len = gsm_stuff_frame(msg->data,
684 						gsm->txframe + 1, msg->len);
685 			gsm->txframe[len + 1] = GSM1_SOF;
686 			len += 2;
687 		} else {
688 			gsm->txframe[0] = GSM0_SOF;
689 			memcpy(gsm->txframe + 1 , msg->data, msg->len);
690 			gsm->txframe[msg->len + 1] = GSM0_SOF;
691 			len = msg->len + 2;
692 		}
693 
694 		if (debug & 4)
695 			print_hex_dump_bytes("gsm_data_kick: ",
696 					     DUMP_PREFIX_OFFSET,
697 					     gsm->txframe, len);
698 		if (gsmld_output(gsm, gsm->txframe, len) <= 0)
699 			break;
700 		/* FIXME: Can eliminate one SOF in many more cases */
701 		gsm->tx_bytes -= msg->len;
702 
703 		list_del(&msg->list);
704 		kfree(msg);
705 
706 		if (dlci) {
707 			tty_port_tty_wakeup(&dlci->port);
708 		} else {
709 			int i = 0;
710 
711 			for (i = 0; i < NUM_DLCI; i++)
712 				if (gsm->dlci[i])
713 					tty_port_tty_wakeup(&gsm->dlci[i]->port);
714 		}
715 	}
716 }
717 
718 /**
719  *	__gsm_data_queue		-	queue a UI or UIH frame
720  *	@dlci: DLCI sending the data
721  *	@msg: message queued
722  *
723  *	Add data to the transmit queue and try and get stuff moving
724  *	out of the mux tty if not already doing so. The Caller must hold
725  *	the gsm tx lock.
726  */
727 
728 static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
729 {
730 	struct gsm_mux *gsm = dlci->gsm;
731 	u8 *dp = msg->data;
732 	u8 *fcs = dp + msg->len;
733 
734 	/* Fill in the header */
735 	if (gsm->encoding == 0) {
736 		if (msg->len < 128)
737 			*--dp = (msg->len << 1) | EA;
738 		else {
739 			*--dp = (msg->len >> 7);	/* bits 7 - 15 */
740 			*--dp = (msg->len & 127) << 1;	/* bits 0 - 6 */
741 		}
742 	}
743 
744 	*--dp = msg->ctrl;
745 	if (gsm->initiator)
746 		*--dp = (msg->addr << 2) | 2 | EA;
747 	else
748 		*--dp = (msg->addr << 2) | EA;
749 	*fcs = gsm_fcs_add_block(INIT_FCS, dp , msg->data - dp);
750 	/* Ugly protocol layering violation */
751 	if (msg->ctrl == UI || msg->ctrl == (UI|PF))
752 		*fcs = gsm_fcs_add_block(*fcs, msg->data, msg->len);
753 	*fcs = 0xFF - *fcs;
754 
755 	gsm_print_packet("Q> ", msg->addr, gsm->initiator, msg->ctrl,
756 							msg->data, msg->len);
757 
758 	/* Move the header back and adjust the length, also allow for the FCS
759 	   now tacked on the end */
760 	msg->len += (msg->data - dp) + 1;
761 	msg->data = dp;
762 
763 	/* Add to the actual output queue */
764 	list_add_tail(&msg->list, &gsm->tx_list);
765 	gsm->tx_bytes += msg->len;
766 	gsm_data_kick(gsm, dlci);
767 }
768 
769 /**
770  *	gsm_data_queue		-	queue a UI or UIH frame
771  *	@dlci: DLCI sending the data
772  *	@msg: message queued
773  *
774  *	Add data to the transmit queue and try and get stuff moving
775  *	out of the mux tty if not already doing so. Take the
776  *	the gsm tx lock and dlci lock.
777  */
778 
779 static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
780 {
781 	unsigned long flags;
782 	spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
783 	__gsm_data_queue(dlci, msg);
784 	spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
785 }
786 
787 /**
788  *	gsm_dlci_data_output	-	try and push data out of a DLCI
789  *	@gsm: mux
790  *	@dlci: the DLCI to pull data from
791  *
792  *	Pull data from a DLCI and send it into the transmit queue if there
793  *	is data. Keep to the MRU of the mux. This path handles the usual tty
794  *	interface which is a byte stream with optional modem data.
795  *
796  *	Caller must hold the tx_lock of the mux.
797  */
798 
799 static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
800 {
801 	struct gsm_msg *msg;
802 	u8 *dp;
803 	int len, total_size, size;
804 	int h = dlci->adaption - 1;
805 
806 	total_size = 0;
807 	while (1) {
808 		len = kfifo_len(&dlci->fifo);
809 		if (len == 0)
810 			return total_size;
811 
812 		/* MTU/MRU count only the data bits */
813 		if (len > gsm->mtu)
814 			len = gsm->mtu;
815 
816 		size = len + h;
817 
818 		msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
819 		/* FIXME: need a timer or something to kick this so it can't
820 		   get stuck with no work outstanding and no buffer free */
821 		if (msg == NULL)
822 			return -ENOMEM;
823 		dp = msg->data;
824 		switch (dlci->adaption) {
825 		case 1:	/* Unstructured */
826 			break;
827 		case 2:	/* Unstructed with modem bits.
828 		Always one byte as we never send inline break data */
829 			*dp++ = gsm_encode_modem(dlci);
830 			break;
831 		}
832 		WARN_ON(kfifo_out_locked(&dlci->fifo, dp , len, &dlci->lock) != len);
833 		__gsm_data_queue(dlci, msg);
834 		total_size += size;
835 	}
836 	/* Bytes of data we used up */
837 	return total_size;
838 }
839 
840 /**
841  *	gsm_dlci_data_output_framed  -	try and push data out of a DLCI
842  *	@gsm: mux
843  *	@dlci: the DLCI to pull data from
844  *
845  *	Pull data from a DLCI and send it into the transmit queue if there
846  *	is data. Keep to the MRU of the mux. This path handles framed data
847  *	queued as skbuffs to the DLCI.
848  *
849  *	Caller must hold the tx_lock of the mux.
850  */
851 
852 static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
853 						struct gsm_dlci *dlci)
854 {
855 	struct gsm_msg *msg;
856 	u8 *dp;
857 	int len, size;
858 	int last = 0, first = 0;
859 	int overhead = 0;
860 
861 	/* One byte per frame is used for B/F flags */
862 	if (dlci->adaption == 4)
863 		overhead = 1;
864 
865 	/* dlci->skb is locked by tx_lock */
866 	if (dlci->skb == NULL) {
867 		dlci->skb = skb_dequeue_tail(&dlci->skb_list);
868 		if (dlci->skb == NULL)
869 			return 0;
870 		first = 1;
871 	}
872 	len = dlci->skb->len + overhead;
873 
874 	/* MTU/MRU count only the data bits */
875 	if (len > gsm->mtu) {
876 		if (dlci->adaption == 3) {
877 			/* Over long frame, bin it */
878 			dev_kfree_skb_any(dlci->skb);
879 			dlci->skb = NULL;
880 			return 0;
881 		}
882 		len = gsm->mtu;
883 	} else
884 		last = 1;
885 
886 	size = len + overhead;
887 	msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype);
888 
889 	/* FIXME: need a timer or something to kick this so it can't
890 	   get stuck with no work outstanding and no buffer free */
891 	if (msg == NULL) {
892 		skb_queue_tail(&dlci->skb_list, dlci->skb);
893 		dlci->skb = NULL;
894 		return -ENOMEM;
895 	}
896 	dp = msg->data;
897 
898 	if (dlci->adaption == 4) { /* Interruptible framed (Packetised Data) */
899 		/* Flag byte to carry the start/end info */
900 		*dp++ = last << 7 | first << 6 | 1;	/* EA */
901 		len--;
902 	}
903 	memcpy(dp, dlci->skb->data, len);
904 	skb_pull(dlci->skb, len);
905 	__gsm_data_queue(dlci, msg);
906 	if (last) {
907 		dev_kfree_skb_any(dlci->skb);
908 		dlci->skb = NULL;
909 	}
910 	return size;
911 }
912 
913 /**
914  *	gsm_dlci_data_sweep		-	look for data to send
915  *	@gsm: the GSM mux
916  *
917  *	Sweep the GSM mux channels in priority order looking for ones with
918  *	data to send. We could do with optimising this scan a bit. We aim
919  *	to fill the queue totally or up to TX_THRESH_HI bytes. Once we hit
920  *	TX_THRESH_LO we get called again
921  *
922  *	FIXME: We should round robin between groups and in theory you can
923  *	renegotiate DLCI priorities with optional stuff. Needs optimising.
924  */
925 
926 static void gsm_dlci_data_sweep(struct gsm_mux *gsm)
927 {
928 	int len;
929 	/* Priority ordering: We should do priority with RR of the groups */
930 	int i = 1;
931 
932 	while (i < NUM_DLCI) {
933 		struct gsm_dlci *dlci;
934 
935 		if (gsm->tx_bytes > TX_THRESH_HI)
936 			break;
937 		dlci = gsm->dlci[i];
938 		if (dlci == NULL || dlci->constipated) {
939 			i++;
940 			continue;
941 		}
942 		if (dlci->adaption < 3 && !dlci->net)
943 			len = gsm_dlci_data_output(gsm, dlci);
944 		else
945 			len = gsm_dlci_data_output_framed(gsm, dlci);
946 		if (len < 0)
947 			break;
948 		/* DLCI empty - try the next */
949 		if (len == 0)
950 			i++;
951 	}
952 }
953 
954 /**
955  *	gsm_dlci_data_kick	-	transmit if possible
956  *	@dlci: DLCI to kick
957  *
958  *	Transmit data from this DLCI if the queue is empty. We can't rely on
959  *	a tty wakeup except when we filled the pipe so we need to fire off
960  *	new data ourselves in other cases.
961  */
962 
963 static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
964 {
965 	unsigned long flags;
966 	int sweep;
967 
968 	if (dlci->constipated)
969 		return;
970 
971 	spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
972 	/* If we have nothing running then we need to fire up */
973 	sweep = (dlci->gsm->tx_bytes < TX_THRESH_LO);
974 	if (dlci->gsm->tx_bytes == 0) {
975 		if (dlci->net)
976 			gsm_dlci_data_output_framed(dlci->gsm, dlci);
977 		else
978 			gsm_dlci_data_output(dlci->gsm, dlci);
979 	}
980 	if (sweep)
981 		gsm_dlci_data_sweep(dlci->gsm);
982 	spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
983 }
984 
985 /*
986  *	Control message processing
987  */
988 
989 
990 /**
991  *	gsm_control_reply	-	send a response frame to a control
992  *	@gsm: gsm channel
993  *	@cmd: the command to use
994  *	@data: data to follow encoded info
995  *	@dlen: length of data
996  *
997  *	Encode up and queue a UI/UIH frame containing our response.
998  */
999 
1000 static void gsm_control_reply(struct gsm_mux *gsm, int cmd, const u8 *data,
1001 					int dlen)
1002 {
1003 	struct gsm_msg *msg;
1004 	msg = gsm_data_alloc(gsm, 0, dlen + 2, gsm->ftype);
1005 	if (msg == NULL)
1006 		return;
1007 	msg->data[0] = (cmd & 0xFE) << 1 | EA;	/* Clear C/R */
1008 	msg->data[1] = (dlen << 1) | EA;
1009 	memcpy(msg->data + 2, data, dlen);
1010 	gsm_data_queue(gsm->dlci[0], msg);
1011 }
1012 
1013 /**
1014  *	gsm_process_modem	-	process received modem status
1015  *	@tty: virtual tty bound to the DLCI
1016  *	@dlci: DLCI to affect
1017  *	@modem: modem bits (full EA)
1018  *	@clen: command length
1019  *
1020  *	Used when a modem control message or line state inline in adaption
1021  *	layer 2 is processed. Sort out the local modem state and throttles
1022  */
1023 
1024 static void gsm_process_modem(struct tty_struct *tty, struct gsm_dlci *dlci,
1025 							u32 modem, int clen)
1026 {
1027 	int  mlines = 0;
1028 	u8 brk = 0;
1029 	int fc;
1030 
1031 	/* The modem status command can either contain one octet (v.24 signals)
1032 	   or two octets (v.24 signals + break signals). The length field will
1033 	   either be 2 or 3 respectively. This is specified in section
1034 	   5.4.6.3.7 of the  27.010 mux spec. */
1035 
1036 	if (clen == 2)
1037 		modem = modem & 0x7f;
1038 	else {
1039 		brk = modem & 0x7f;
1040 		modem = (modem >> 7) & 0x7f;
1041 	}
1042 
1043 	/* Flow control/ready to communicate */
1044 	fc = (modem & MDM_FC) || !(modem & MDM_RTR);
1045 	if (fc && !dlci->constipated) {
1046 		/* Need to throttle our output on this device */
1047 		dlci->constipated = true;
1048 	} else if (!fc && dlci->constipated) {
1049 		dlci->constipated = false;
1050 		gsm_dlci_data_kick(dlci);
1051 	}
1052 
1053 	/* Map modem bits */
1054 	if (modem & MDM_RTC)
1055 		mlines |= TIOCM_DSR | TIOCM_DTR;
1056 	if (modem & MDM_RTR)
1057 		mlines |= TIOCM_RTS | TIOCM_CTS;
1058 	if (modem & MDM_IC)
1059 		mlines |= TIOCM_RI;
1060 	if (modem & MDM_DV)
1061 		mlines |= TIOCM_CD;
1062 
1063 	/* Carrier drop -> hangup */
1064 	if (tty) {
1065 		if ((mlines & TIOCM_CD) == 0 && (dlci->modem_rx & TIOCM_CD))
1066 			if (!C_CLOCAL(tty))
1067 				tty_hangup(tty);
1068 	}
1069 	if (brk & 0x01)
1070 		tty_insert_flip_char(&dlci->port, 0, TTY_BREAK);
1071 	dlci->modem_rx = mlines;
1072 }
1073 
1074 /**
1075  *	gsm_control_modem	-	modem status received
1076  *	@gsm: GSM channel
1077  *	@data: data following command
1078  *	@clen: command length
1079  *
1080  *	We have received a modem status control message. This is used by
1081  *	the GSM mux protocol to pass virtual modem line status and optionally
1082  *	to indicate break signals. Unpack it, convert to Linux representation
1083  *	and if need be stuff a break message down the tty.
1084  */
1085 
1086 static void gsm_control_modem(struct gsm_mux *gsm, const u8 *data, int clen)
1087 {
1088 	unsigned int addr = 0;
1089 	unsigned int modem = 0;
1090 	unsigned int brk = 0;
1091 	struct gsm_dlci *dlci;
1092 	int len = clen;
1093 	const u8 *dp = data;
1094 	struct tty_struct *tty;
1095 
1096 	while (gsm_read_ea(&addr, *dp++) == 0) {
1097 		len--;
1098 		if (len == 0)
1099 			return;
1100 	}
1101 	/* Must be at least one byte following the EA */
1102 	len--;
1103 	if (len <= 0)
1104 		return;
1105 
1106 	addr >>= 1;
1107 	/* Closed port, or invalid ? */
1108 	if (addr == 0 || addr >= NUM_DLCI || gsm->dlci[addr] == NULL)
1109 		return;
1110 	dlci = gsm->dlci[addr];
1111 
1112 	while (gsm_read_ea(&modem, *dp++) == 0) {
1113 		len--;
1114 		if (len == 0)
1115 			return;
1116 	}
1117 	len--;
1118 	if (len > 0) {
1119 		while (gsm_read_ea(&brk, *dp++) == 0) {
1120 			len--;
1121 			if (len == 0)
1122 				return;
1123 		}
1124 		modem <<= 7;
1125 		modem |= (brk & 0x7f);
1126 	}
1127 	tty = tty_port_tty_get(&dlci->port);
1128 	gsm_process_modem(tty, dlci, modem, clen);
1129 	if (tty) {
1130 		tty_wakeup(tty);
1131 		tty_kref_put(tty);
1132 	}
1133 	gsm_control_reply(gsm, CMD_MSC, data, clen);
1134 }
1135 
1136 /**
1137  *	gsm_control_rls		-	remote line status
1138  *	@gsm: GSM channel
1139  *	@data: data bytes
1140  *	@clen: data length
1141  *
1142  *	The modem sends us a two byte message on the control channel whenever
1143  *	it wishes to send us an error state from the virtual link. Stuff
1144  *	this into the uplink tty if present
1145  */
1146 
1147 static void gsm_control_rls(struct gsm_mux *gsm, const u8 *data, int clen)
1148 {
1149 	struct tty_port *port;
1150 	unsigned int addr = 0;
1151 	u8 bits;
1152 	int len = clen;
1153 	const u8 *dp = data;
1154 
1155 	while (gsm_read_ea(&addr, *dp++) == 0) {
1156 		len--;
1157 		if (len == 0)
1158 			return;
1159 	}
1160 	/* Must be at least one byte following ea */
1161 	len--;
1162 	if (len <= 0)
1163 		return;
1164 	addr >>= 1;
1165 	/* Closed port, or invalid ? */
1166 	if (addr == 0 || addr >= NUM_DLCI || gsm->dlci[addr] == NULL)
1167 		return;
1168 	/* No error ? */
1169 	bits = *dp;
1170 	if ((bits & 1) == 0)
1171 		return;
1172 
1173 	port = &gsm->dlci[addr]->port;
1174 
1175 	if (bits & 2)
1176 		tty_insert_flip_char(port, 0, TTY_OVERRUN);
1177 	if (bits & 4)
1178 		tty_insert_flip_char(port, 0, TTY_PARITY);
1179 	if (bits & 8)
1180 		tty_insert_flip_char(port, 0, TTY_FRAME);
1181 
1182 	tty_flip_buffer_push(port);
1183 
1184 	gsm_control_reply(gsm, CMD_RLS, data, clen);
1185 }
1186 
1187 static void gsm_dlci_begin_close(struct gsm_dlci *dlci);
1188 static void gsm_dlci_close(struct gsm_dlci *dlci);
1189 
1190 /**
1191  *	gsm_control_message	-	DLCI 0 control processing
1192  *	@gsm: our GSM mux
1193  *	@command:  the command EA
1194  *	@data: data beyond the command/length EAs
1195  *	@clen: length
1196  *
1197  *	Input processor for control messages from the other end of the link.
1198  *	Processes the incoming request and queues a response frame or an
1199  *	NSC response if not supported
1200  */
1201 
1202 static void gsm_control_message(struct gsm_mux *gsm, unsigned int command,
1203 						const u8 *data, int clen)
1204 {
1205 	u8 buf[1];
1206 	unsigned long flags;
1207 	struct gsm_dlci *dlci;
1208 	int i;
1209 	int address;
1210 
1211 	switch (command) {
1212 	case CMD_CLD: {
1213 		if (addr_cnt > 0) {
1214 			for (i = 0; i < addr_cnt; i++) {
1215 				address = addr_open[i];
1216 				dlci = gsm->dlci[address];
1217 				gsm_dlci_close(dlci);
1218 				addr_open[i] = 0;
1219 			}
1220 		}
1221 		/* Modem wishes to close down */
1222 		dlci = gsm->dlci[0];
1223 		if (dlci) {
1224 			dlci->dead = true;
1225 			gsm->dead = true;
1226 			gsm_dlci_close(dlci);
1227 			addr_cnt = 0;
1228 			gsm_response(gsm, 0, UA|PF);
1229 		}
1230 		}
1231 		break;
1232 	case CMD_TEST:
1233 		/* Modem wishes to test, reply with the data */
1234 		gsm_control_reply(gsm, CMD_TEST, data, clen);
1235 		break;
1236 	case CMD_FCON:
1237 		/* Modem can accept data again */
1238 		gsm->constipated = false;
1239 		gsm_control_reply(gsm, CMD_FCON, NULL, 0);
1240 		/* Kick the link in case it is idling */
1241 		spin_lock_irqsave(&gsm->tx_lock, flags);
1242 		gsm_data_kick(gsm, NULL);
1243 		spin_unlock_irqrestore(&gsm->tx_lock, flags);
1244 		break;
1245 	case CMD_FCOFF:
1246 		/* Modem wants us to STFU */
1247 		gsm->constipated = true;
1248 		gsm_control_reply(gsm, CMD_FCOFF, NULL, 0);
1249 		break;
1250 	case CMD_MSC:
1251 		/* Out of band modem line change indicator for a DLCI */
1252 		gsm_control_modem(gsm, data, clen);
1253 		break;
1254 	case CMD_RLS:
1255 		/* Out of band error reception for a DLCI */
1256 		gsm_control_rls(gsm, data, clen);
1257 		break;
1258 	case CMD_PSC:
1259 		/* Modem wishes to enter power saving state */
1260 		gsm_control_reply(gsm, CMD_PSC, NULL, 0);
1261 		break;
1262 		/* Optional unsupported commands */
1263 	case CMD_PN:	/* Parameter negotiation */
1264 	case CMD_RPN:	/* Remote port negotiation */
1265 	case CMD_SNC:	/* Service negotiation command */
1266 	default:
1267 		/* Reply to bad commands with an NSC */
1268 		buf[0] = command;
1269 		gsm_control_reply(gsm, CMD_NSC, buf, 1);
1270 		break;
1271 	}
1272 }
1273 
1274 /**
1275  *	gsm_control_response	-	process a response to our control
1276  *	@gsm: our GSM mux
1277  *	@command: the command (response) EA
1278  *	@data: data beyond the command/length EA
1279  *	@clen: length
1280  *
1281  *	Process a response to an outstanding command. We only allow a single
1282  *	control message in flight so this is fairly easy. All the clean up
1283  *	is done by the caller, we just update the fields, flag it as done
1284  *	and return
1285  */
1286 
1287 static void gsm_control_response(struct gsm_mux *gsm, unsigned int command,
1288 						const u8 *data, int clen)
1289 {
1290 	struct gsm_control *ctrl;
1291 	unsigned long flags;
1292 
1293 	spin_lock_irqsave(&gsm->control_lock, flags);
1294 
1295 	ctrl = gsm->pending_cmd;
1296 	/* Does the reply match our command */
1297 	command |= 1;
1298 	if (ctrl != NULL && (command == ctrl->cmd || command == CMD_NSC)) {
1299 		/* Our command was replied to, kill the retry timer */
1300 		del_timer(&gsm->t2_timer);
1301 		gsm->pending_cmd = NULL;
1302 		/* Rejected by the other end */
1303 		if (command == CMD_NSC)
1304 			ctrl->error = -EOPNOTSUPP;
1305 		ctrl->done = 1;
1306 		wake_up(&gsm->event);
1307 	}
1308 	spin_unlock_irqrestore(&gsm->control_lock, flags);
1309 }
1310 
1311 /**
1312  *	gsm_control_transmit	-	send control packet
1313  *	@gsm: gsm mux
1314  *	@ctrl: frame to send
1315  *
1316  *	Send out a pending control command (called under control lock)
1317  */
1318 
1319 static void gsm_control_transmit(struct gsm_mux *gsm, struct gsm_control *ctrl)
1320 {
1321 	struct gsm_msg *msg = gsm_data_alloc(gsm, 0, ctrl->len + 1, gsm->ftype);
1322 	if (msg == NULL)
1323 		return;
1324 	msg->data[0] = (ctrl->cmd << 1) | 2 | EA;	/* command */
1325 	memcpy(msg->data + 1, ctrl->data, ctrl->len);
1326 	gsm_data_queue(gsm->dlci[0], msg);
1327 }
1328 
1329 /**
1330  *	gsm_control_retransmit	-	retransmit a control frame
1331  *	@t: timer contained in our gsm object
1332  *
1333  *	Called off the T2 timer expiry in order to retransmit control frames
1334  *	that have been lost in the system somewhere. The control_lock protects
1335  *	us from colliding with another sender or a receive completion event.
1336  *	In that situation the timer may still occur in a small window but
1337  *	gsm->pending_cmd will be NULL and we just let the timer expire.
1338  */
1339 
1340 static void gsm_control_retransmit(struct timer_list *t)
1341 {
1342 	struct gsm_mux *gsm = from_timer(gsm, t, t2_timer);
1343 	struct gsm_control *ctrl;
1344 	unsigned long flags;
1345 	spin_lock_irqsave(&gsm->control_lock, flags);
1346 	ctrl = gsm->pending_cmd;
1347 	if (ctrl) {
1348 		gsm->cretries--;
1349 		if (gsm->cretries == 0) {
1350 			gsm->pending_cmd = NULL;
1351 			ctrl->error = -ETIMEDOUT;
1352 			ctrl->done = 1;
1353 			spin_unlock_irqrestore(&gsm->control_lock, flags);
1354 			wake_up(&gsm->event);
1355 			return;
1356 		}
1357 		gsm_control_transmit(gsm, ctrl);
1358 		mod_timer(&gsm->t2_timer, jiffies + gsm->t2 * HZ / 100);
1359 	}
1360 	spin_unlock_irqrestore(&gsm->control_lock, flags);
1361 }
1362 
1363 /**
1364  *	gsm_control_send	-	send a control frame on DLCI 0
1365  *	@gsm: the GSM channel
1366  *	@command: command  to send including CR bit
1367  *	@data: bytes of data (must be kmalloced)
1368  *	@clen: length of the block to send
1369  *
1370  *	Queue and dispatch a control command. Only one command can be
1371  *	active at a time. In theory more can be outstanding but the matching
1372  *	gets really complicated so for now stick to one outstanding.
1373  */
1374 
1375 static struct gsm_control *gsm_control_send(struct gsm_mux *gsm,
1376 		unsigned int command, u8 *data, int clen)
1377 {
1378 	struct gsm_control *ctrl = kzalloc(sizeof(struct gsm_control),
1379 						GFP_KERNEL);
1380 	unsigned long flags;
1381 	if (ctrl == NULL)
1382 		return NULL;
1383 retry:
1384 	wait_event(gsm->event, gsm->pending_cmd == NULL);
1385 	spin_lock_irqsave(&gsm->control_lock, flags);
1386 	if (gsm->pending_cmd != NULL) {
1387 		spin_unlock_irqrestore(&gsm->control_lock, flags);
1388 		goto retry;
1389 	}
1390 	ctrl->cmd = command;
1391 	ctrl->data = data;
1392 	ctrl->len = clen;
1393 	gsm->pending_cmd = ctrl;
1394 
1395 	/* If DLCI0 is in ADM mode skip retries, it won't respond */
1396 	if (gsm->dlci[0]->mode == DLCI_MODE_ADM)
1397 		gsm->cretries = 1;
1398 	else
1399 		gsm->cretries = gsm->n2;
1400 
1401 	mod_timer(&gsm->t2_timer, jiffies + gsm->t2 * HZ / 100);
1402 	gsm_control_transmit(gsm, ctrl);
1403 	spin_unlock_irqrestore(&gsm->control_lock, flags);
1404 	return ctrl;
1405 }
1406 
1407 /**
1408  *	gsm_control_wait	-	wait for a control to finish
1409  *	@gsm: GSM mux
1410  *	@control: control we are waiting on
1411  *
1412  *	Waits for the control to complete or time out. Frees any used
1413  *	resources and returns 0 for success, or an error if the remote
1414  *	rejected or ignored the request.
1415  */
1416 
1417 static int gsm_control_wait(struct gsm_mux *gsm, struct gsm_control *control)
1418 {
1419 	int err;
1420 	wait_event(gsm->event, control->done == 1);
1421 	err = control->error;
1422 	kfree(control);
1423 	return err;
1424 }
1425 
1426 
1427 /*
1428  *	DLCI level handling: Needs krefs
1429  */
1430 
1431 /*
1432  *	State transitions and timers
1433  */
1434 
1435 /**
1436  *	gsm_dlci_close		-	a DLCI has closed
1437  *	@dlci: DLCI that closed
1438  *
1439  *	Perform processing when moving a DLCI into closed state. If there
1440  *	is an attached tty this is hung up
1441  */
1442 
1443 static void gsm_dlci_close(struct gsm_dlci *dlci)
1444 {
1445 	del_timer(&dlci->t1);
1446 	if (debug & 8)
1447 		pr_debug("DLCI %d goes closed.\n", dlci->addr);
1448 	dlci->state = DLCI_CLOSED;
1449 	if (dlci->addr != 0) {
1450 		tty_port_tty_hangup(&dlci->port, false);
1451 		kfifo_reset(&dlci->fifo);
1452 	} else
1453 		dlci->gsm->dead = true;
1454 	/* Unregister gsmtty driver,report gsmtty dev remove uevent for user */
1455 	tty_unregister_device(gsm_tty_driver, dlci->addr);
1456 	wake_up(&dlci->gsm->event);
1457 	/* A DLCI 0 close is a MUX termination so we need to kick that
1458 	   back to userspace somehow */
1459 }
1460 
1461 /**
1462  *	gsm_dlci_open		-	a DLCI has opened
1463  *	@dlci: DLCI that opened
1464  *
1465  *	Perform processing when moving a DLCI into open state.
1466  */
1467 
1468 static void gsm_dlci_open(struct gsm_dlci *dlci)
1469 {
1470 	/* Note that SABM UA .. SABM UA first UA lost can mean that we go
1471 	   open -> open */
1472 	del_timer(&dlci->t1);
1473 	/* This will let a tty open continue */
1474 	dlci->state = DLCI_OPEN;
1475 	if (debug & 8)
1476 		pr_debug("DLCI %d goes open.\n", dlci->addr);
1477 	/* Register gsmtty driver,report gsmtty dev add uevent for user */
1478 	tty_register_device(gsm_tty_driver, dlci->addr, NULL);
1479 	wake_up(&dlci->gsm->event);
1480 }
1481 
1482 /**
1483  *	gsm_dlci_t1		-	T1 timer expiry
1484  *	@t: timer contained in the DLCI that opened
1485  *
1486  *	The T1 timer handles retransmits of control frames (essentially of
1487  *	SABM and DISC). We resend the command until the retry count runs out
1488  *	in which case an opening port goes back to closed and a closing port
1489  *	is simply put into closed state (any further frames from the other
1490  *	end will get a DM response)
1491  *
1492  *	Some control dlci can stay in ADM mode with other dlci working just
1493  *	fine. In that case we can just keep the control dlci open after the
1494  *	DLCI_OPENING retries time out.
1495  */
1496 
1497 static void gsm_dlci_t1(struct timer_list *t)
1498 {
1499 	struct gsm_dlci *dlci = from_timer(dlci, t, t1);
1500 	struct gsm_mux *gsm = dlci->gsm;
1501 
1502 	switch (dlci->state) {
1503 	case DLCI_OPENING:
1504 		dlci->retries--;
1505 		if (dlci->retries) {
1506 			gsm_command(dlci->gsm, dlci->addr, SABM|PF);
1507 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
1508 		} else if (!dlci->addr && gsm->control == (DM | PF)) {
1509 			if (debug & 8)
1510 				pr_info("DLCI %d opening in ADM mode.\n",
1511 					dlci->addr);
1512 			dlci->mode = DLCI_MODE_ADM;
1513 			gsm_dlci_open(dlci);
1514 		} else {
1515 			gsm_dlci_close(dlci);
1516 		}
1517 
1518 		break;
1519 	case DLCI_CLOSING:
1520 		dlci->retries--;
1521 		if (dlci->retries) {
1522 			gsm_command(dlci->gsm, dlci->addr, DISC|PF);
1523 			mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
1524 		} else
1525 			gsm_dlci_close(dlci);
1526 		break;
1527 	default:
1528 		pr_debug("%s: unhandled state: %d\n", __func__, dlci->state);
1529 		break;
1530 	}
1531 }
1532 
1533 /**
1534  *	gsm_dlci_begin_open	-	start channel open procedure
1535  *	@dlci: DLCI to open
1536  *
1537  *	Commence opening a DLCI from the Linux side. We issue SABM messages
1538  *	to the modem which should then reply with a UA or ADM, at which point
1539  *	we will move into open state. Opening is done asynchronously with retry
1540  *	running off timers and the responses.
1541  */
1542 
1543 static void gsm_dlci_begin_open(struct gsm_dlci *dlci)
1544 {
1545 	struct gsm_mux *gsm = dlci->gsm;
1546 	if (dlci->state == DLCI_OPEN || dlci->state == DLCI_OPENING)
1547 		return;
1548 	dlci->retries = gsm->n2;
1549 	dlci->state = DLCI_OPENING;
1550 	gsm_command(dlci->gsm, dlci->addr, SABM|PF);
1551 	mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
1552 }
1553 
1554 /**
1555  *	gsm_dlci_begin_close	-	start channel open procedure
1556  *	@dlci: DLCI to open
1557  *
1558  *	Commence closing a DLCI from the Linux side. We issue DISC messages
1559  *	to the modem which should then reply with a UA, at which point we
1560  *	will move into closed state. Closing is done asynchronously with retry
1561  *	off timers. We may also receive a DM reply from the other end which
1562  *	indicates the channel was already closed.
1563  */
1564 
1565 static void gsm_dlci_begin_close(struct gsm_dlci *dlci)
1566 {
1567 	struct gsm_mux *gsm = dlci->gsm;
1568 	if (dlci->state == DLCI_CLOSED || dlci->state == DLCI_CLOSING)
1569 		return;
1570 	dlci->retries = gsm->n2;
1571 	dlci->state = DLCI_CLOSING;
1572 	gsm_command(dlci->gsm, dlci->addr, DISC|PF);
1573 	mod_timer(&dlci->t1, jiffies + gsm->t1 * HZ / 100);
1574 }
1575 
1576 /**
1577  *	gsm_dlci_data		-	data arrived
1578  *	@dlci: channel
1579  *	@data: block of bytes received
1580  *	@clen: length of received block
1581  *
1582  *	A UI or UIH frame has arrived which contains data for a channel
1583  *	other than the control channel. If the relevant virtual tty is
1584  *	open we shovel the bits down it, if not we drop them.
1585  */
1586 
1587 static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen)
1588 {
1589 	/* krefs .. */
1590 	struct tty_port *port = &dlci->port;
1591 	struct tty_struct *tty;
1592 	unsigned int modem = 0;
1593 	int len = clen;
1594 
1595 	if (debug & 16)
1596 		pr_debug("%d bytes for tty\n", len);
1597 	switch (dlci->adaption)  {
1598 	/* Unsupported types */
1599 	case 4:		/* Packetised interruptible data */
1600 		break;
1601 	case 3:		/* Packetised uininterruptible voice/data */
1602 		break;
1603 	case 2:		/* Asynchronous serial with line state in each frame */
1604 		while (gsm_read_ea(&modem, *data++) == 0) {
1605 			len--;
1606 			if (len == 0)
1607 				return;
1608 		}
1609 		tty = tty_port_tty_get(port);
1610 		if (tty) {
1611 			gsm_process_modem(tty, dlci, modem, clen);
1612 			tty_kref_put(tty);
1613 		}
1614 		fallthrough;
1615 	case 1:		/* Line state will go via DLCI 0 controls only */
1616 	default:
1617 		tty_insert_flip_string(port, data, len);
1618 		tty_flip_buffer_push(port);
1619 	}
1620 }
1621 
1622 /**
1623  *	gsm_dlci_command	-	data arrived on control channel
1624  *	@dlci: channel
1625  *	@data: block of bytes received
1626  *	@len: length of received block
1627  *
1628  *	A UI or UIH frame has arrived which contains data for DLCI 0 the
1629  *	control channel. This should contain a command EA followed by
1630  *	control data bytes. The command EA contains a command/response bit
1631  *	and we divide up the work accordingly.
1632  */
1633 
1634 static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
1635 {
1636 	/* See what command is involved */
1637 	unsigned int command = 0;
1638 	while (len-- > 0) {
1639 		if (gsm_read_ea(&command, *data++) == 1) {
1640 			int clen = *data++;
1641 			len--;
1642 			/* FIXME: this is properly an EA */
1643 			clen >>= 1;
1644 			/* Malformed command ? */
1645 			if (clen > len)
1646 				return;
1647 			if (command & 1)
1648 				gsm_control_message(dlci->gsm, command,
1649 								data, clen);
1650 			else
1651 				gsm_control_response(dlci->gsm, command,
1652 								data, clen);
1653 			return;
1654 		}
1655 	}
1656 }
1657 
1658 /*
1659  *	Allocate/Free DLCI channels
1660  */
1661 
1662 /**
1663  *	gsm_dlci_alloc		-	allocate a DLCI
1664  *	@gsm: GSM mux
1665  *	@addr: address of the DLCI
1666  *
1667  *	Allocate and install a new DLCI object into the GSM mux.
1668  *
1669  *	FIXME: review locking races
1670  */
1671 
1672 static struct gsm_dlci *gsm_dlci_alloc(struct gsm_mux *gsm, int addr)
1673 {
1674 	struct gsm_dlci *dlci = kzalloc(sizeof(struct gsm_dlci), GFP_ATOMIC);
1675 	if (dlci == NULL)
1676 		return NULL;
1677 	spin_lock_init(&dlci->lock);
1678 	mutex_init(&dlci->mutex);
1679 	if (kfifo_alloc(&dlci->fifo, 4096, GFP_KERNEL) < 0) {
1680 		kfree(dlci);
1681 		return NULL;
1682 	}
1683 
1684 	skb_queue_head_init(&dlci->skb_list);
1685 	timer_setup(&dlci->t1, gsm_dlci_t1, 0);
1686 	tty_port_init(&dlci->port);
1687 	dlci->port.ops = &gsm_port_ops;
1688 	dlci->gsm = gsm;
1689 	dlci->addr = addr;
1690 	dlci->adaption = gsm->adaption;
1691 	dlci->state = DLCI_CLOSED;
1692 	if (addr)
1693 		dlci->data = gsm_dlci_data;
1694 	else
1695 		dlci->data = gsm_dlci_command;
1696 	gsm->dlci[addr] = dlci;
1697 	return dlci;
1698 }
1699 
1700 /**
1701  *	gsm_dlci_free		-	free DLCI
1702  *	@port: tty port for DLCI to free
1703  *
1704  *	Free up a DLCI.
1705  *
1706  *	Can sleep.
1707  */
1708 static void gsm_dlci_free(struct tty_port *port)
1709 {
1710 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
1711 
1712 	del_timer_sync(&dlci->t1);
1713 	dlci->gsm->dlci[dlci->addr] = NULL;
1714 	kfifo_free(&dlci->fifo);
1715 	while ((dlci->skb = skb_dequeue(&dlci->skb_list)))
1716 		dev_kfree_skb(dlci->skb);
1717 	kfree(dlci);
1718 }
1719 
1720 static inline void dlci_get(struct gsm_dlci *dlci)
1721 {
1722 	tty_port_get(&dlci->port);
1723 }
1724 
1725 static inline void dlci_put(struct gsm_dlci *dlci)
1726 {
1727 	tty_port_put(&dlci->port);
1728 }
1729 
1730 static void gsm_destroy_network(struct gsm_dlci *dlci);
1731 
1732 /**
1733  *	gsm_dlci_release		-	release DLCI
1734  *	@dlci: DLCI to destroy
1735  *
1736  *	Release a DLCI. Actual free is deferred until either
1737  *	mux is closed or tty is closed - whichever is last.
1738  *
1739  *	Can sleep.
1740  */
1741 static void gsm_dlci_release(struct gsm_dlci *dlci)
1742 {
1743 	struct tty_struct *tty = tty_port_tty_get(&dlci->port);
1744 	if (tty) {
1745 		mutex_lock(&dlci->mutex);
1746 		gsm_destroy_network(dlci);
1747 		mutex_unlock(&dlci->mutex);
1748 
1749 		tty_hangup(tty);
1750 
1751 		tty_port_tty_set(&dlci->port, NULL);
1752 		tty_kref_put(tty);
1753 	}
1754 	dlci->state = DLCI_CLOSED;
1755 	dlci_put(dlci);
1756 }
1757 
1758 /*
1759  *	LAPBish link layer logic
1760  */
1761 
1762 /**
1763  *	gsm_queue		-	a GSM frame is ready to process
1764  *	@gsm: pointer to our gsm mux
1765  *
1766  *	At this point in time a frame has arrived and been demangled from
1767  *	the line encoding. All the differences between the encodings have
1768  *	been handled below us and the frame is unpacked into the structures.
1769  *	The fcs holds the header FCS but any data FCS must be added here.
1770  */
1771 
1772 static void gsm_queue(struct gsm_mux *gsm)
1773 {
1774 	struct gsm_dlci *dlci;
1775 	u8 cr;
1776 	int address;
1777 	int i, j, k, address_tmp;
1778 	/* We have to sneak a look at the packet body to do the FCS.
1779 	   A somewhat layering violation in the spec */
1780 
1781 	if ((gsm->control & ~PF) == UI)
1782 		gsm->fcs = gsm_fcs_add_block(gsm->fcs, gsm->buf, gsm->len);
1783 	if (gsm->encoding == 0) {
1784 		/* WARNING: gsm->received_fcs is used for
1785 		gsm->encoding = 0 only.
1786 		In this case it contain the last piece of data
1787 		required to generate final CRC */
1788 		gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->received_fcs);
1789 	}
1790 	if (gsm->fcs != GOOD_FCS) {
1791 		gsm->bad_fcs++;
1792 		if (debug & 4)
1793 			pr_debug("BAD FCS %02x\n", gsm->fcs);
1794 		return;
1795 	}
1796 	address = gsm->address >> 1;
1797 	if (address >= NUM_DLCI)
1798 		goto invalid;
1799 
1800 	cr = gsm->address & 1;		/* C/R bit */
1801 
1802 	gsm_print_packet("<--", address, cr, gsm->control, gsm->buf, gsm->len);
1803 
1804 	cr ^= 1 - gsm->initiator;	/* Flip so 1 always means command */
1805 	dlci = gsm->dlci[address];
1806 
1807 	switch (gsm->control) {
1808 	case SABM|PF:
1809 		if (cr == 1)
1810 			goto invalid;
1811 		if (dlci == NULL)
1812 			dlci = gsm_dlci_alloc(gsm, address);
1813 		if (dlci == NULL)
1814 			return;
1815 		if (dlci->dead)
1816 			gsm_response(gsm, address, DM|PF);
1817 		else {
1818 			gsm_response(gsm, address, UA|PF);
1819 			gsm_dlci_open(dlci);
1820 			/* Save dlci open address */
1821 			if (address) {
1822 				addr_open[addr_cnt] = address;
1823 				addr_cnt++;
1824 			}
1825 		}
1826 		break;
1827 	case DISC|PF:
1828 		if (cr == 1)
1829 			goto invalid;
1830 		if (dlci == NULL || dlci->state == DLCI_CLOSED) {
1831 			gsm_response(gsm, address, DM|PF);
1832 			return;
1833 		}
1834 		/* Real close complete */
1835 		if (!address) {
1836 			if (addr_cnt > 0) {
1837 				for (i = 0; i < addr_cnt; i++) {
1838 					address = addr_open[i];
1839 					dlci = gsm->dlci[address];
1840 					gsm_dlci_close(dlci);
1841 					addr_open[i] = 0;
1842 				}
1843 			}
1844 			dlci = gsm->dlci[0];
1845 			gsm_dlci_close(dlci);
1846 			addr_cnt = 0;
1847 			gsm_response(gsm, 0, UA|PF);
1848 		} else {
1849 			gsm_response(gsm, address, UA|PF);
1850 			gsm_dlci_close(dlci);
1851 			/* clear dlci address */
1852 			for (j = 0; j < addr_cnt; j++) {
1853 				address_tmp = addr_open[j];
1854 				if (address_tmp == address) {
1855 					for (k = j; k < addr_cnt; k++)
1856 						addr_open[k] = addr_open[k+1];
1857 					addr_cnt--;
1858 					break;
1859 				}
1860 			}
1861 		}
1862 		break;
1863 	case UA:
1864 	case UA|PF:
1865 		if (cr == 0 || dlci == NULL)
1866 			break;
1867 		switch (dlci->state) {
1868 		case DLCI_CLOSING:
1869 			gsm_dlci_close(dlci);
1870 			break;
1871 		case DLCI_OPENING:
1872 			gsm_dlci_open(dlci);
1873 			break;
1874 		default:
1875 			pr_debug("%s: unhandled state: %d\n", __func__,
1876 					dlci->state);
1877 			break;
1878 		}
1879 		break;
1880 	case DM:	/* DM can be valid unsolicited */
1881 	case DM|PF:
1882 		if (cr)
1883 			goto invalid;
1884 		if (dlci == NULL)
1885 			return;
1886 		gsm_dlci_close(dlci);
1887 		break;
1888 	case UI:
1889 	case UI|PF:
1890 	case UIH:
1891 	case UIH|PF:
1892 #if 0
1893 		if (cr)
1894 			goto invalid;
1895 #endif
1896 		if (dlci == NULL || dlci->state != DLCI_OPEN) {
1897 			gsm_command(gsm, address, DM|PF);
1898 			return;
1899 		}
1900 		dlci->data(dlci, gsm->buf, gsm->len);
1901 		break;
1902 	default:
1903 		goto invalid;
1904 	}
1905 	return;
1906 invalid:
1907 	gsm->malformed++;
1908 	return;
1909 }
1910 
1911 
1912 /**
1913  *	gsm0_receive	-	perform processing for non-transparency
1914  *	@gsm: gsm data for this ldisc instance
1915  *	@c: character
1916  *
1917  *	Receive bytes in gsm mode 0
1918  */
1919 
1920 static void gsm0_receive(struct gsm_mux *gsm, unsigned char c)
1921 {
1922 	unsigned int len;
1923 
1924 	switch (gsm->state) {
1925 	case GSM_SEARCH:	/* SOF marker */
1926 		if (c == GSM0_SOF) {
1927 			gsm->state = GSM_ADDRESS;
1928 			gsm->address = 0;
1929 			gsm->len = 0;
1930 			gsm->fcs = INIT_FCS;
1931 		}
1932 		break;
1933 	case GSM_ADDRESS:	/* Address EA */
1934 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
1935 		if (gsm_read_ea(&gsm->address, c))
1936 			gsm->state = GSM_CONTROL;
1937 		break;
1938 	case GSM_CONTROL:	/* Control Byte */
1939 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
1940 		gsm->control = c;
1941 		gsm->state = GSM_LEN0;
1942 		break;
1943 	case GSM_LEN0:		/* Length EA */
1944 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
1945 		if (gsm_read_ea(&gsm->len, c)) {
1946 			if (gsm->len > gsm->mru) {
1947 				gsm->bad_size++;
1948 				gsm->state = GSM_SEARCH;
1949 				break;
1950 			}
1951 			gsm->count = 0;
1952 			if (!gsm->len)
1953 				gsm->state = GSM_FCS;
1954 			else
1955 				gsm->state = GSM_DATA;
1956 			break;
1957 		}
1958 		gsm->state = GSM_LEN1;
1959 		break;
1960 	case GSM_LEN1:
1961 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
1962 		len = c;
1963 		gsm->len |= len << 7;
1964 		if (gsm->len > gsm->mru) {
1965 			gsm->bad_size++;
1966 			gsm->state = GSM_SEARCH;
1967 			break;
1968 		}
1969 		gsm->count = 0;
1970 		if (!gsm->len)
1971 			gsm->state = GSM_FCS;
1972 		else
1973 			gsm->state = GSM_DATA;
1974 		break;
1975 	case GSM_DATA:		/* Data */
1976 		gsm->buf[gsm->count++] = c;
1977 		if (gsm->count == gsm->len)
1978 			gsm->state = GSM_FCS;
1979 		break;
1980 	case GSM_FCS:		/* FCS follows the packet */
1981 		gsm->received_fcs = c;
1982 		gsm_queue(gsm);
1983 		gsm->state = GSM_SSOF;
1984 		break;
1985 	case GSM_SSOF:
1986 		if (c == GSM0_SOF) {
1987 			gsm->state = GSM_SEARCH;
1988 			break;
1989 		}
1990 		break;
1991 	default:
1992 		pr_debug("%s: unhandled state: %d\n", __func__, gsm->state);
1993 		break;
1994 	}
1995 }
1996 
1997 /**
1998  *	gsm1_receive	-	perform processing for non-transparency
1999  *	@gsm: gsm data for this ldisc instance
2000  *	@c: character
2001  *
2002  *	Receive bytes in mode 1 (Advanced option)
2003  */
2004 
2005 static void gsm1_receive(struct gsm_mux *gsm, unsigned char c)
2006 {
2007 	if (c == GSM1_SOF) {
2008 		/* EOF is only valid in frame if we have got to the data state
2009 		   and received at least one byte (the FCS) */
2010 		if (gsm->state == GSM_DATA && gsm->count) {
2011 			/* Extract the FCS */
2012 			gsm->count--;
2013 			gsm->fcs = gsm_fcs_add(gsm->fcs, gsm->buf[gsm->count]);
2014 			gsm->len = gsm->count;
2015 			gsm_queue(gsm);
2016 			gsm->state  = GSM_START;
2017 			return;
2018 		}
2019 		/* Any partial frame was a runt so go back to start */
2020 		if (gsm->state != GSM_START) {
2021 			gsm->malformed++;
2022 			gsm->state = GSM_START;
2023 		}
2024 		/* A SOF in GSM_START means we are still reading idling or
2025 		   framing bytes */
2026 		return;
2027 	}
2028 
2029 	if (c == GSM1_ESCAPE) {
2030 		gsm->escape = true;
2031 		return;
2032 	}
2033 
2034 	/* Only an unescaped SOF gets us out of GSM search */
2035 	if (gsm->state == GSM_SEARCH)
2036 		return;
2037 
2038 	if (gsm->escape) {
2039 		c ^= GSM1_ESCAPE_BITS;
2040 		gsm->escape = false;
2041 	}
2042 	switch (gsm->state) {
2043 	case GSM_START:		/* First byte after SOF */
2044 		gsm->address = 0;
2045 		gsm->state = GSM_ADDRESS;
2046 		gsm->fcs = INIT_FCS;
2047 		fallthrough;
2048 	case GSM_ADDRESS:	/* Address continuation */
2049 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2050 		if (gsm_read_ea(&gsm->address, c))
2051 			gsm->state = GSM_CONTROL;
2052 		break;
2053 	case GSM_CONTROL:	/* Control Byte */
2054 		gsm->fcs = gsm_fcs_add(gsm->fcs, c);
2055 		gsm->control = c;
2056 		gsm->count = 0;
2057 		gsm->state = GSM_DATA;
2058 		break;
2059 	case GSM_DATA:		/* Data */
2060 		if (gsm->count > gsm->mru) {	/* Allow one for the FCS */
2061 			gsm->state = GSM_OVERRUN;
2062 			gsm->bad_size++;
2063 		} else
2064 			gsm->buf[gsm->count++] = c;
2065 		break;
2066 	case GSM_OVERRUN:	/* Over-long - eg a dropped SOF */
2067 		break;
2068 	default:
2069 		pr_debug("%s: unhandled state: %d\n", __func__, gsm->state);
2070 		break;
2071 	}
2072 }
2073 
2074 /**
2075  *	gsm_error		-	handle tty error
2076  *	@gsm: ldisc data
2077  *
2078  *	Handle an error in the receipt of data for a frame. Currently we just
2079  *	go back to hunting for a SOF.
2080  *
2081  *	FIXME: better diagnostics ?
2082  */
2083 
2084 static void gsm_error(struct gsm_mux *gsm)
2085 {
2086 	gsm->state = GSM_SEARCH;
2087 	gsm->io_error++;
2088 }
2089 
2090 static int gsm_disconnect(struct gsm_mux *gsm)
2091 {
2092 	struct gsm_dlci *dlci = gsm->dlci[0];
2093 	struct gsm_control *gc;
2094 
2095 	if (!dlci)
2096 		return 0;
2097 
2098 	/* In theory disconnecting DLCI 0 is sufficient but for some
2099 	   modems this is apparently not the case. */
2100 	gc = gsm_control_send(gsm, CMD_CLD, NULL, 0);
2101 	if (gc)
2102 		gsm_control_wait(gsm, gc);
2103 
2104 	del_timer_sync(&gsm->t2_timer);
2105 	/* Now we are sure T2 has stopped */
2106 
2107 	gsm_dlci_begin_close(dlci);
2108 	wait_event_interruptible(gsm->event,
2109 				dlci->state == DLCI_CLOSED);
2110 
2111 	if (signal_pending(current))
2112 		return -EINTR;
2113 
2114 	return 0;
2115 }
2116 
2117 /**
2118  *	gsm_cleanup_mux		-	generic GSM protocol cleanup
2119  *	@gsm: our mux
2120  *
2121  *	Clean up the bits of the mux which are the same for all framing
2122  *	protocols. Remove the mux from the mux table, stop all the timers
2123  *	and then shut down each device hanging up the channels as we go.
2124  */
2125 
2126 static void gsm_cleanup_mux(struct gsm_mux *gsm)
2127 {
2128 	int i;
2129 	struct gsm_dlci *dlci = gsm->dlci[0];
2130 	struct gsm_msg *txq, *ntxq;
2131 
2132 	gsm->dead = true;
2133 
2134 	spin_lock(&gsm_mux_lock);
2135 	for (i = 0; i < MAX_MUX; i++) {
2136 		if (gsm_mux[i] == gsm) {
2137 			gsm_mux[i] = NULL;
2138 			break;
2139 		}
2140 	}
2141 	spin_unlock(&gsm_mux_lock);
2142 	/* open failed before registering => nothing to do */
2143 	if (i == MAX_MUX)
2144 		return;
2145 
2146 	del_timer_sync(&gsm->t2_timer);
2147 	/* Now we are sure T2 has stopped */
2148 	if (dlci)
2149 		dlci->dead = true;
2150 
2151 	/* Free up any link layer users */
2152 	mutex_lock(&gsm->mutex);
2153 	for (i = 0; i < NUM_DLCI; i++)
2154 		if (gsm->dlci[i])
2155 			gsm_dlci_release(gsm->dlci[i]);
2156 	mutex_unlock(&gsm->mutex);
2157 	/* Now wipe the queues */
2158 	list_for_each_entry_safe(txq, ntxq, &gsm->tx_list, list)
2159 		kfree(txq);
2160 	INIT_LIST_HEAD(&gsm->tx_list);
2161 }
2162 
2163 /**
2164  *	gsm_activate_mux	-	generic GSM setup
2165  *	@gsm: our mux
2166  *
2167  *	Set up the bits of the mux which are the same for all framing
2168  *	protocols. Add the mux to the mux table so it can be opened and
2169  *	finally kick off connecting to DLCI 0 on the modem.
2170  */
2171 
2172 static int gsm_activate_mux(struct gsm_mux *gsm)
2173 {
2174 	struct gsm_dlci *dlci;
2175 	int i = 0;
2176 
2177 	timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
2178 	init_waitqueue_head(&gsm->event);
2179 	spin_lock_init(&gsm->control_lock);
2180 	spin_lock_init(&gsm->tx_lock);
2181 
2182 	if (gsm->encoding == 0)
2183 		gsm->receive = gsm0_receive;
2184 	else
2185 		gsm->receive = gsm1_receive;
2186 
2187 	spin_lock(&gsm_mux_lock);
2188 	for (i = 0; i < MAX_MUX; i++) {
2189 		if (gsm_mux[i] == NULL) {
2190 			gsm->num = i;
2191 			gsm_mux[i] = gsm;
2192 			break;
2193 		}
2194 	}
2195 	spin_unlock(&gsm_mux_lock);
2196 	if (i == MAX_MUX)
2197 		return -EBUSY;
2198 
2199 	dlci = gsm_dlci_alloc(gsm, 0);
2200 	if (dlci == NULL)
2201 		return -ENOMEM;
2202 	gsm->dead = false;		/* Tty opens are now permissible */
2203 	return 0;
2204 }
2205 
2206 /**
2207  *	gsm_free_mux		-	free up a mux
2208  *	@gsm: mux to free
2209  *
2210  *	Dispose of allocated resources for a dead mux
2211  */
2212 static void gsm_free_mux(struct gsm_mux *gsm)
2213 {
2214 	kfree(gsm->txframe);
2215 	kfree(gsm->buf);
2216 	kfree(gsm);
2217 }
2218 
2219 /**
2220  *	gsm_free_muxr		-	free up a mux
2221  *	@ref: kreference to the mux to free
2222  *
2223  *	Dispose of allocated resources for a dead mux
2224  */
2225 static void gsm_free_muxr(struct kref *ref)
2226 {
2227 	struct gsm_mux *gsm = container_of(ref, struct gsm_mux, ref);
2228 	gsm_free_mux(gsm);
2229 }
2230 
2231 static inline void mux_get(struct gsm_mux *gsm)
2232 {
2233 	kref_get(&gsm->ref);
2234 }
2235 
2236 static inline void mux_put(struct gsm_mux *gsm)
2237 {
2238 	kref_put(&gsm->ref, gsm_free_muxr);
2239 }
2240 
2241 static inline unsigned int mux_num_to_base(struct gsm_mux *gsm)
2242 {
2243 	return gsm->num * NUM_DLCI;
2244 }
2245 
2246 static inline unsigned int mux_line_to_num(unsigned int line)
2247 {
2248 	return line / NUM_DLCI;
2249 }
2250 
2251 /**
2252  *	gsm_alloc_mux		-	allocate a mux
2253  *
2254  *	Creates a new mux ready for activation.
2255  */
2256 
2257 static struct gsm_mux *gsm_alloc_mux(void)
2258 {
2259 	struct gsm_mux *gsm = kzalloc(sizeof(struct gsm_mux), GFP_KERNEL);
2260 	if (gsm == NULL)
2261 		return NULL;
2262 	gsm->buf = kmalloc(MAX_MRU + 1, GFP_KERNEL);
2263 	if (gsm->buf == NULL) {
2264 		kfree(gsm);
2265 		return NULL;
2266 	}
2267 	gsm->txframe = kmalloc(2 * MAX_MRU + 2, GFP_KERNEL);
2268 	if (gsm->txframe == NULL) {
2269 		kfree(gsm->buf);
2270 		kfree(gsm);
2271 		return NULL;
2272 	}
2273 	spin_lock_init(&gsm->lock);
2274 	mutex_init(&gsm->mutex);
2275 	kref_init(&gsm->ref);
2276 	INIT_LIST_HEAD(&gsm->tx_list);
2277 
2278 	gsm->t1 = T1;
2279 	gsm->t2 = T2;
2280 	gsm->n2 = N2;
2281 	gsm->ftype = UIH;
2282 	gsm->adaption = 1;
2283 	gsm->encoding = 1;
2284 	gsm->mru = 64;	/* Default to encoding 1 so these should be 64 */
2285 	gsm->mtu = 64;
2286 	gsm->dead = true;	/* Avoid early tty opens */
2287 
2288 	return gsm;
2289 }
2290 
2291 static void gsm_copy_config_values(struct gsm_mux *gsm,
2292 				   struct gsm_config *c)
2293 {
2294 	memset(c, 0, sizeof(*c));
2295 	c->adaption = gsm->adaption;
2296 	c->encapsulation = gsm->encoding;
2297 	c->initiator = gsm->initiator;
2298 	c->t1 = gsm->t1;
2299 	c->t2 = gsm->t2;
2300 	c->t3 = 0;	/* Not supported */
2301 	c->n2 = gsm->n2;
2302 	if (gsm->ftype == UIH)
2303 		c->i = 1;
2304 	else
2305 		c->i = 2;
2306 	pr_debug("Ftype %d i %d\n", gsm->ftype, c->i);
2307 	c->mru = gsm->mru;
2308 	c->mtu = gsm->mtu;
2309 	c->k = 0;
2310 }
2311 
2312 static int gsm_config(struct gsm_mux *gsm, struct gsm_config *c)
2313 {
2314 	int need_close = 0;
2315 	int need_restart = 0;
2316 
2317 	/* Stuff we don't support yet - UI or I frame transport, windowing */
2318 	if ((c->adaption != 1 && c->adaption != 2) || c->k)
2319 		return -EOPNOTSUPP;
2320 	/* Check the MRU/MTU range looks sane */
2321 	if (c->mru > MAX_MRU || c->mtu > MAX_MTU || c->mru < 8 || c->mtu < 8)
2322 		return -EINVAL;
2323 	if (c->n2 < 3)
2324 		return -EINVAL;
2325 	if (c->encapsulation > 1)	/* Basic, advanced, no I */
2326 		return -EINVAL;
2327 	if (c->initiator > 1)
2328 		return -EINVAL;
2329 	if (c->i == 0 || c->i > 2)	/* UIH and UI only */
2330 		return -EINVAL;
2331 	/*
2332 	 * See what is needed for reconfiguration
2333 	 */
2334 
2335 	/* Timing fields */
2336 	if (c->t1 != 0 && c->t1 != gsm->t1)
2337 		need_restart = 1;
2338 	if (c->t2 != 0 && c->t2 != gsm->t2)
2339 		need_restart = 1;
2340 	if (c->encapsulation != gsm->encoding)
2341 		need_restart = 1;
2342 	if (c->adaption != gsm->adaption)
2343 		need_restart = 1;
2344 	/* Requires care */
2345 	if (c->initiator != gsm->initiator)
2346 		need_close = 1;
2347 	if (c->mru != gsm->mru)
2348 		need_restart = 1;
2349 	if (c->mtu != gsm->mtu)
2350 		need_restart = 1;
2351 
2352 	/*
2353 	 * Close down what is needed, restart and initiate the new
2354 	 * configuration
2355 	 */
2356 
2357 	if (gsm->initiator && (need_close || need_restart)) {
2358 		int ret;
2359 
2360 		ret = gsm_disconnect(gsm);
2361 
2362 		if (ret)
2363 			return ret;
2364 	}
2365 	if (need_restart)
2366 		gsm_cleanup_mux(gsm);
2367 
2368 	gsm->initiator = c->initiator;
2369 	gsm->mru = c->mru;
2370 	gsm->mtu = c->mtu;
2371 	gsm->encoding = c->encapsulation;
2372 	gsm->adaption = c->adaption;
2373 	gsm->n2 = c->n2;
2374 
2375 	if (c->i == 1)
2376 		gsm->ftype = UIH;
2377 	else if (c->i == 2)
2378 		gsm->ftype = UI;
2379 
2380 	if (c->t1)
2381 		gsm->t1 = c->t1;
2382 	if (c->t2)
2383 		gsm->t2 = c->t2;
2384 
2385 	/*
2386 	 * FIXME: We need to separate activation/deactivation from adding
2387 	 * and removing from the mux array
2388 	 */
2389 	if (need_restart)
2390 		gsm_activate_mux(gsm);
2391 	if (gsm->initiator && need_close)
2392 		gsm_dlci_begin_open(gsm->dlci[0]);
2393 	return 0;
2394 }
2395 
2396 /**
2397  *	gsmld_output		-	write to link
2398  *	@gsm: our mux
2399  *	@data: bytes to output
2400  *	@len: size
2401  *
2402  *	Write a block of data from the GSM mux to the data channel. This
2403  *	will eventually be serialized from above but at the moment isn't.
2404  */
2405 
2406 static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
2407 {
2408 	if (tty_write_room(gsm->tty) < len) {
2409 		set_bit(TTY_DO_WRITE_WAKEUP, &gsm->tty->flags);
2410 		return -ENOSPC;
2411 	}
2412 	if (debug & 4)
2413 		print_hex_dump_bytes("gsmld_output: ", DUMP_PREFIX_OFFSET,
2414 				     data, len);
2415 	return gsm->tty->ops->write(gsm->tty, data, len);
2416 }
2417 
2418 /**
2419  *	gsmld_attach_gsm	-	mode set up
2420  *	@tty: our tty structure
2421  *	@gsm: our mux
2422  *
2423  *	Set up the MUX for basic mode and commence connecting to the
2424  *	modem. Currently called from the line discipline set up but
2425  *	will need moving to an ioctl path.
2426  */
2427 
2428 static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
2429 {
2430 	unsigned int base;
2431 	int ret, i;
2432 
2433 	gsm->tty = tty_kref_get(tty);
2434 	ret =  gsm_activate_mux(gsm);
2435 	if (ret != 0)
2436 		tty_kref_put(gsm->tty);
2437 	else {
2438 		/* Don't register device 0 - this is the control channel and not
2439 		   a usable tty interface */
2440 		if (gsm->initiator) {
2441 			base = mux_num_to_base(gsm); /* Base for this MUX */
2442 			for (i = 1; i < NUM_DLCI; i++) {
2443 				struct device *dev;
2444 
2445 				dev = tty_register_device(gsm_tty_driver,
2446 							base + i, NULL);
2447 				if (IS_ERR(dev)) {
2448 					for (i--; i >= 1; i--)
2449 						tty_unregister_device(gsm_tty_driver,
2450 									base + i);
2451 					return PTR_ERR(dev);
2452 				}
2453 			}
2454 		}
2455 	}
2456 	return ret;
2457 }
2458 
2459 
2460 /**
2461  *	gsmld_detach_gsm	-	stop doing 0710 mux
2462  *	@tty: tty attached to the mux
2463  *	@gsm: mux
2464  *
2465  *	Shutdown and then clean up the resources used by the line discipline
2466  */
2467 
2468 static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
2469 {
2470 	unsigned int base = mux_num_to_base(gsm); /* Base for this MUX */
2471 	int i;
2472 
2473 	WARN_ON(tty != gsm->tty);
2474 	if (gsm->initiator) {
2475 		for (i = 1; i < NUM_DLCI; i++)
2476 			tty_unregister_device(gsm_tty_driver, base + i);
2477 	}
2478 	gsm_cleanup_mux(gsm);
2479 	tty_kref_put(gsm->tty);
2480 	gsm->tty = NULL;
2481 }
2482 
2483 static void gsmld_receive_buf(struct tty_struct *tty, const unsigned char *cp,
2484 			      const char *fp, int count)
2485 {
2486 	struct gsm_mux *gsm = tty->disc_data;
2487 	char flags = TTY_NORMAL;
2488 
2489 	if (debug & 4)
2490 		print_hex_dump_bytes("gsmld_receive: ", DUMP_PREFIX_OFFSET,
2491 				     cp, count);
2492 
2493 	for (; count; count--, cp++) {
2494 		if (fp)
2495 			flags = *fp++;
2496 		switch (flags) {
2497 		case TTY_NORMAL:
2498 			gsm->receive(gsm, *cp);
2499 			break;
2500 		case TTY_OVERRUN:
2501 		case TTY_BREAK:
2502 		case TTY_PARITY:
2503 		case TTY_FRAME:
2504 			gsm_error(gsm);
2505 			break;
2506 		default:
2507 			WARN_ONCE(1, "%s: unknown flag %d\n",
2508 			       tty_name(tty), flags);
2509 			break;
2510 		}
2511 	}
2512 	/* FASYNC if needed ? */
2513 	/* If clogged call tty_throttle(tty); */
2514 }
2515 
2516 /**
2517  *	gsmld_flush_buffer	-	clean input queue
2518  *	@tty:	terminal device
2519  *
2520  *	Flush the input buffer. Called when the line discipline is
2521  *	being closed, when the tty layer wants the buffer flushed (eg
2522  *	at hangup).
2523  */
2524 
2525 static void gsmld_flush_buffer(struct tty_struct *tty)
2526 {
2527 }
2528 
2529 /**
2530  *	gsmld_close		-	close the ldisc for this tty
2531  *	@tty: device
2532  *
2533  *	Called from the terminal layer when this line discipline is
2534  *	being shut down, either because of a close or becsuse of a
2535  *	discipline change. The function will not be called while other
2536  *	ldisc methods are in progress.
2537  */
2538 
2539 static void gsmld_close(struct tty_struct *tty)
2540 {
2541 	struct gsm_mux *gsm = tty->disc_data;
2542 
2543 	gsmld_detach_gsm(tty, gsm);
2544 
2545 	gsmld_flush_buffer(tty);
2546 	/* Do other clean up here */
2547 	mux_put(gsm);
2548 }
2549 
2550 /**
2551  *	gsmld_open		-	open an ldisc
2552  *	@tty: terminal to open
2553  *
2554  *	Called when this line discipline is being attached to the
2555  *	terminal device. Can sleep. Called serialized so that no
2556  *	other events will occur in parallel. No further open will occur
2557  *	until a close.
2558  */
2559 
2560 static int gsmld_open(struct tty_struct *tty)
2561 {
2562 	struct gsm_mux *gsm;
2563 	int ret;
2564 
2565 	if (tty->ops->write == NULL)
2566 		return -EINVAL;
2567 
2568 	/* Attach our ldisc data */
2569 	gsm = gsm_alloc_mux();
2570 	if (gsm == NULL)
2571 		return -ENOMEM;
2572 
2573 	tty->disc_data = gsm;
2574 	tty->receive_room = 65536;
2575 
2576 	/* Attach the initial passive connection */
2577 	gsm->encoding = 1;
2578 
2579 	ret = gsmld_attach_gsm(tty, gsm);
2580 	if (ret != 0) {
2581 		gsm_cleanup_mux(gsm);
2582 		mux_put(gsm);
2583 	}
2584 	return ret;
2585 }
2586 
2587 /**
2588  *	gsmld_write_wakeup	-	asynchronous I/O notifier
2589  *	@tty: tty device
2590  *
2591  *	Required for the ptys, serial driver etc. since processes
2592  *	that attach themselves to the master and rely on ASYNC
2593  *	IO must be woken up
2594  */
2595 
2596 static void gsmld_write_wakeup(struct tty_struct *tty)
2597 {
2598 	struct gsm_mux *gsm = tty->disc_data;
2599 	unsigned long flags;
2600 
2601 	/* Queue poll */
2602 	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2603 	spin_lock_irqsave(&gsm->tx_lock, flags);
2604 	gsm_data_kick(gsm, NULL);
2605 	if (gsm->tx_bytes < TX_THRESH_LO) {
2606 		gsm_dlci_data_sweep(gsm);
2607 	}
2608 	spin_unlock_irqrestore(&gsm->tx_lock, flags);
2609 }
2610 
2611 /**
2612  *	gsmld_read		-	read function for tty
2613  *	@tty: tty device
2614  *	@file: file object
2615  *	@buf: userspace buffer pointer
2616  *	@nr: size of I/O
2617  *	@cookie: unused
2618  *	@offset: unused
2619  *
2620  *	Perform reads for the line discipline. We are guaranteed that the
2621  *	line discipline will not be closed under us but we may get multiple
2622  *	parallel readers and must handle this ourselves. We may also get
2623  *	a hangup. Always called in user context, may sleep.
2624  *
2625  *	This code must be sure never to sleep through a hangup.
2626  */
2627 
2628 static ssize_t gsmld_read(struct tty_struct *tty, struct file *file,
2629 			  unsigned char *buf, size_t nr,
2630 			  void **cookie, unsigned long offset)
2631 {
2632 	return -EOPNOTSUPP;
2633 }
2634 
2635 /**
2636  *	gsmld_write		-	write function for tty
2637  *	@tty: tty device
2638  *	@file: file object
2639  *	@buf: userspace buffer pointer
2640  *	@nr: size of I/O
2641  *
2642  *	Called when the owner of the device wants to send a frame
2643  *	itself (or some other control data). The data is transferred
2644  *	as-is and must be properly framed and checksummed as appropriate
2645  *	by userspace. Frames are either sent whole or not at all as this
2646  *	avoids pain user side.
2647  */
2648 
2649 static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
2650 			   const unsigned char *buf, size_t nr)
2651 {
2652 	int space = tty_write_room(tty);
2653 	if (space >= nr)
2654 		return tty->ops->write(tty, buf, nr);
2655 	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2656 	return -ENOBUFS;
2657 }
2658 
2659 /**
2660  *	gsmld_poll		-	poll method for N_GSM0710
2661  *	@tty: terminal device
2662  *	@file: file accessing it
2663  *	@wait: poll table
2664  *
2665  *	Called when the line discipline is asked to poll() for data or
2666  *	for special events. This code is not serialized with respect to
2667  *	other events save open/close.
2668  *
2669  *	This code must be sure never to sleep through a hangup.
2670  *	Called without the kernel lock held - fine
2671  */
2672 
2673 static __poll_t gsmld_poll(struct tty_struct *tty, struct file *file,
2674 							poll_table *wait)
2675 {
2676 	__poll_t mask = 0;
2677 	struct gsm_mux *gsm = tty->disc_data;
2678 
2679 	poll_wait(file, &tty->read_wait, wait);
2680 	poll_wait(file, &tty->write_wait, wait);
2681 	if (tty_hung_up_p(file))
2682 		mask |= EPOLLHUP;
2683 	if (!tty_is_writelocked(tty) && tty_write_room(tty) > 0)
2684 		mask |= EPOLLOUT | EPOLLWRNORM;
2685 	if (gsm->dead)
2686 		mask |= EPOLLHUP;
2687 	return mask;
2688 }
2689 
2690 static int gsmld_ioctl(struct tty_struct *tty, unsigned int cmd,
2691 		       unsigned long arg)
2692 {
2693 	struct gsm_config c;
2694 	struct gsm_mux *gsm = tty->disc_data;
2695 	unsigned int base;
2696 
2697 	switch (cmd) {
2698 	case GSMIOC_GETCONF:
2699 		gsm_copy_config_values(gsm, &c);
2700 		if (copy_to_user((void __user *)arg, &c, sizeof(c)))
2701 			return -EFAULT;
2702 		return 0;
2703 	case GSMIOC_SETCONF:
2704 		if (copy_from_user(&c, (void __user *)arg, sizeof(c)))
2705 			return -EFAULT;
2706 		return gsm_config(gsm, &c);
2707 	case GSMIOC_GETFIRST:
2708 		base = mux_num_to_base(gsm);
2709 		return put_user(base + 1, (__u32 __user *)arg);
2710 	default:
2711 		return n_tty_ioctl_helper(tty, cmd, arg);
2712 	}
2713 }
2714 
2715 /*
2716  *	Network interface
2717  *
2718  */
2719 
2720 static int gsm_mux_net_open(struct net_device *net)
2721 {
2722 	pr_debug("%s called\n", __func__);
2723 	netif_start_queue(net);
2724 	return 0;
2725 }
2726 
2727 static int gsm_mux_net_close(struct net_device *net)
2728 {
2729 	netif_stop_queue(net);
2730 	return 0;
2731 }
2732 
2733 static void dlci_net_free(struct gsm_dlci *dlci)
2734 {
2735 	if (!dlci->net) {
2736 		WARN_ON(1);
2737 		return;
2738 	}
2739 	dlci->adaption = dlci->prev_adaption;
2740 	dlci->data = dlci->prev_data;
2741 	free_netdev(dlci->net);
2742 	dlci->net = NULL;
2743 }
2744 static void net_free(struct kref *ref)
2745 {
2746 	struct gsm_mux_net *mux_net;
2747 	struct gsm_dlci *dlci;
2748 
2749 	mux_net = container_of(ref, struct gsm_mux_net, ref);
2750 	dlci = mux_net->dlci;
2751 
2752 	if (dlci->net) {
2753 		unregister_netdev(dlci->net);
2754 		dlci_net_free(dlci);
2755 	}
2756 }
2757 
2758 static inline void muxnet_get(struct gsm_mux_net *mux_net)
2759 {
2760 	kref_get(&mux_net->ref);
2761 }
2762 
2763 static inline void muxnet_put(struct gsm_mux_net *mux_net)
2764 {
2765 	kref_put(&mux_net->ref, net_free);
2766 }
2767 
2768 static netdev_tx_t gsm_mux_net_start_xmit(struct sk_buff *skb,
2769 				      struct net_device *net)
2770 {
2771 	struct gsm_mux_net *mux_net = netdev_priv(net);
2772 	struct gsm_dlci *dlci = mux_net->dlci;
2773 	muxnet_get(mux_net);
2774 
2775 	skb_queue_head(&dlci->skb_list, skb);
2776 	net->stats.tx_packets++;
2777 	net->stats.tx_bytes += skb->len;
2778 	gsm_dlci_data_kick(dlci);
2779 	/* And tell the kernel when the last transmit started. */
2780 	netif_trans_update(net);
2781 	muxnet_put(mux_net);
2782 	return NETDEV_TX_OK;
2783 }
2784 
2785 /* called when a packet did not ack after watchdogtimeout */
2786 static void gsm_mux_net_tx_timeout(struct net_device *net, unsigned int txqueue)
2787 {
2788 	/* Tell syslog we are hosed. */
2789 	dev_dbg(&net->dev, "Tx timed out.\n");
2790 
2791 	/* Update statistics */
2792 	net->stats.tx_errors++;
2793 }
2794 
2795 static void gsm_mux_rx_netchar(struct gsm_dlci *dlci,
2796 				const unsigned char *in_buf, int size)
2797 {
2798 	struct net_device *net = dlci->net;
2799 	struct sk_buff *skb;
2800 	struct gsm_mux_net *mux_net = netdev_priv(net);
2801 	muxnet_get(mux_net);
2802 
2803 	/* Allocate an sk_buff */
2804 	skb = dev_alloc_skb(size + NET_IP_ALIGN);
2805 	if (!skb) {
2806 		/* We got no receive buffer. */
2807 		net->stats.rx_dropped++;
2808 		muxnet_put(mux_net);
2809 		return;
2810 	}
2811 	skb_reserve(skb, NET_IP_ALIGN);
2812 	skb_put_data(skb, in_buf, size);
2813 
2814 	skb->dev = net;
2815 	skb->protocol = htons(ETH_P_IP);
2816 
2817 	/* Ship it off to the kernel */
2818 	netif_rx(skb);
2819 
2820 	/* update out statistics */
2821 	net->stats.rx_packets++;
2822 	net->stats.rx_bytes += size;
2823 	muxnet_put(mux_net);
2824 	return;
2825 }
2826 
2827 static void gsm_mux_net_init(struct net_device *net)
2828 {
2829 	static const struct net_device_ops gsm_netdev_ops = {
2830 		.ndo_open		= gsm_mux_net_open,
2831 		.ndo_stop		= gsm_mux_net_close,
2832 		.ndo_start_xmit		= gsm_mux_net_start_xmit,
2833 		.ndo_tx_timeout		= gsm_mux_net_tx_timeout,
2834 	};
2835 
2836 	net->netdev_ops = &gsm_netdev_ops;
2837 
2838 	/* fill in the other fields */
2839 	net->watchdog_timeo = GSM_NET_TX_TIMEOUT;
2840 	net->flags = IFF_POINTOPOINT | IFF_NOARP | IFF_MULTICAST;
2841 	net->type = ARPHRD_NONE;
2842 	net->tx_queue_len = 10;
2843 }
2844 
2845 
2846 /* caller holds the dlci mutex */
2847 static void gsm_destroy_network(struct gsm_dlci *dlci)
2848 {
2849 	struct gsm_mux_net *mux_net;
2850 
2851 	pr_debug("destroy network interface\n");
2852 	if (!dlci->net)
2853 		return;
2854 	mux_net = netdev_priv(dlci->net);
2855 	muxnet_put(mux_net);
2856 }
2857 
2858 
2859 /* caller holds the dlci mutex */
2860 static int gsm_create_network(struct gsm_dlci *dlci, struct gsm_netconfig *nc)
2861 {
2862 	char *netname;
2863 	int retval = 0;
2864 	struct net_device *net;
2865 	struct gsm_mux_net *mux_net;
2866 
2867 	if (!capable(CAP_NET_ADMIN))
2868 		return -EPERM;
2869 
2870 	/* Already in a non tty mode */
2871 	if (dlci->adaption > 2)
2872 		return -EBUSY;
2873 
2874 	if (nc->protocol != htons(ETH_P_IP))
2875 		return -EPROTONOSUPPORT;
2876 
2877 	if (nc->adaption != 3 && nc->adaption != 4)
2878 		return -EPROTONOSUPPORT;
2879 
2880 	pr_debug("create network interface\n");
2881 
2882 	netname = "gsm%d";
2883 	if (nc->if_name[0] != '\0')
2884 		netname = nc->if_name;
2885 	net = alloc_netdev(sizeof(struct gsm_mux_net), netname,
2886 			   NET_NAME_UNKNOWN, gsm_mux_net_init);
2887 	if (!net) {
2888 		pr_err("alloc_netdev failed\n");
2889 		return -ENOMEM;
2890 	}
2891 	net->mtu = dlci->gsm->mtu;
2892 	net->min_mtu = 8;
2893 	net->max_mtu = dlci->gsm->mtu;
2894 	mux_net = netdev_priv(net);
2895 	mux_net->dlci = dlci;
2896 	kref_init(&mux_net->ref);
2897 	strncpy(nc->if_name, net->name, IFNAMSIZ); /* return net name */
2898 
2899 	/* reconfigure dlci for network */
2900 	dlci->prev_adaption = dlci->adaption;
2901 	dlci->prev_data = dlci->data;
2902 	dlci->adaption = nc->adaption;
2903 	dlci->data = gsm_mux_rx_netchar;
2904 	dlci->net = net;
2905 
2906 	pr_debug("register netdev\n");
2907 	retval = register_netdev(net);
2908 	if (retval) {
2909 		pr_err("network register fail %d\n", retval);
2910 		dlci_net_free(dlci);
2911 		return retval;
2912 	}
2913 	return net->ifindex;	/* return network index */
2914 }
2915 
2916 /* Line discipline for real tty */
2917 static struct tty_ldisc_ops tty_ldisc_packet = {
2918 	.owner		 = THIS_MODULE,
2919 	.num		 = N_GSM0710,
2920 	.name            = "n_gsm",
2921 	.open            = gsmld_open,
2922 	.close           = gsmld_close,
2923 	.flush_buffer    = gsmld_flush_buffer,
2924 	.read            = gsmld_read,
2925 	.write           = gsmld_write,
2926 	.ioctl           = gsmld_ioctl,
2927 	.poll            = gsmld_poll,
2928 	.receive_buf     = gsmld_receive_buf,
2929 	.write_wakeup    = gsmld_write_wakeup
2930 };
2931 
2932 /*
2933  *	Virtual tty side
2934  */
2935 
2936 #define TX_SIZE		512
2937 
2938 static int gsmtty_modem_update(struct gsm_dlci *dlci, u8 brk)
2939 {
2940 	u8 modembits[5];
2941 	struct gsm_control *ctrl;
2942 	int len = 2;
2943 
2944 	if (brk)
2945 		len++;
2946 
2947 	modembits[0] = len << 1 | EA;		/* Data bytes */
2948 	modembits[1] = dlci->addr << 2 | 3;	/* DLCI, EA, 1 */
2949 	modembits[2] = gsm_encode_modem(dlci) << 1 | EA;
2950 	if (brk)
2951 		modembits[3] = brk << 4 | 2 | EA;	/* Valid, EA */
2952 	ctrl = gsm_control_send(dlci->gsm, CMD_MSC, modembits, len + 1);
2953 	if (ctrl == NULL)
2954 		return -ENOMEM;
2955 	return gsm_control_wait(dlci->gsm, ctrl);
2956 }
2957 
2958 static int gsm_carrier_raised(struct tty_port *port)
2959 {
2960 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
2961 	struct gsm_mux *gsm = dlci->gsm;
2962 
2963 	/* Not yet open so no carrier info */
2964 	if (dlci->state != DLCI_OPEN)
2965 		return 0;
2966 	if (debug & 2)
2967 		return 1;
2968 
2969 	/*
2970 	 * Basic mode with control channel in ADM mode may not respond
2971 	 * to CMD_MSC at all and modem_rx is empty.
2972 	 */
2973 	if (gsm->encoding == 0 && gsm->dlci[0]->mode == DLCI_MODE_ADM &&
2974 	    !dlci->modem_rx)
2975 		return 1;
2976 
2977 	return dlci->modem_rx & TIOCM_CD;
2978 }
2979 
2980 static void gsm_dtr_rts(struct tty_port *port, int onoff)
2981 {
2982 	struct gsm_dlci *dlci = container_of(port, struct gsm_dlci, port);
2983 	unsigned int modem_tx = dlci->modem_tx;
2984 	if (onoff)
2985 		modem_tx |= TIOCM_DTR | TIOCM_RTS;
2986 	else
2987 		modem_tx &= ~(TIOCM_DTR | TIOCM_RTS);
2988 	if (modem_tx != dlci->modem_tx) {
2989 		dlci->modem_tx = modem_tx;
2990 		gsmtty_modem_update(dlci, 0);
2991 	}
2992 }
2993 
2994 static const struct tty_port_operations gsm_port_ops = {
2995 	.carrier_raised = gsm_carrier_raised,
2996 	.dtr_rts = gsm_dtr_rts,
2997 	.destruct = gsm_dlci_free,
2998 };
2999 
3000 static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
3001 {
3002 	struct gsm_mux *gsm;
3003 	struct gsm_dlci *dlci;
3004 	unsigned int line = tty->index;
3005 	unsigned int mux = mux_line_to_num(line);
3006 	bool alloc = false;
3007 	int ret;
3008 
3009 	line = line & 0x3F;
3010 
3011 	if (mux >= MAX_MUX)
3012 		return -ENXIO;
3013 	/* FIXME: we need to lock gsm_mux for lifetimes of ttys eventually */
3014 	if (gsm_mux[mux] == NULL)
3015 		return -EUNATCH;
3016 	if (line == 0 || line > 61)	/* 62/63 reserved */
3017 		return -ECHRNG;
3018 	gsm = gsm_mux[mux];
3019 	if (gsm->dead)
3020 		return -EL2HLT;
3021 	/* If DLCI 0 is not yet fully open return an error.
3022 	This is ok from a locking
3023 	perspective as we don't have to worry about this
3024 	if DLCI0 is lost */
3025 	mutex_lock(&gsm->mutex);
3026 	if (gsm->dlci[0] && gsm->dlci[0]->state != DLCI_OPEN) {
3027 		mutex_unlock(&gsm->mutex);
3028 		return -EL2NSYNC;
3029 	}
3030 	dlci = gsm->dlci[line];
3031 	if (dlci == NULL) {
3032 		alloc = true;
3033 		dlci = gsm_dlci_alloc(gsm, line);
3034 	}
3035 	if (dlci == NULL) {
3036 		mutex_unlock(&gsm->mutex);
3037 		return -ENOMEM;
3038 	}
3039 	ret = tty_port_install(&dlci->port, driver, tty);
3040 	if (ret) {
3041 		if (alloc)
3042 			dlci_put(dlci);
3043 		mutex_unlock(&gsm->mutex);
3044 		return ret;
3045 	}
3046 
3047 	dlci_get(dlci);
3048 	dlci_get(gsm->dlci[0]);
3049 	mux_get(gsm);
3050 	tty->driver_data = dlci;
3051 	mutex_unlock(&gsm->mutex);
3052 
3053 	return 0;
3054 }
3055 
3056 static int gsmtty_open(struct tty_struct *tty, struct file *filp)
3057 {
3058 	struct gsm_dlci *dlci = tty->driver_data;
3059 	struct tty_port *port = &dlci->port;
3060 	struct gsm_mux *gsm = dlci->gsm;
3061 
3062 	port->count++;
3063 	tty_port_tty_set(port, tty);
3064 
3065 	dlci->modem_rx = 0;
3066 	/* We could in theory open and close before we wait - eg if we get
3067 	   a DM straight back. This is ok as that will have caused a hangup */
3068 	tty_port_set_initialized(port, 1);
3069 	/* Start sending off SABM messages */
3070 	if (gsm->initiator)
3071 		gsm_dlci_begin_open(dlci);
3072 	/* And wait for virtual carrier */
3073 	return tty_port_block_til_ready(port, tty, filp);
3074 }
3075 
3076 static void gsmtty_close(struct tty_struct *tty, struct file *filp)
3077 {
3078 	struct gsm_dlci *dlci = tty->driver_data;
3079 
3080 	if (dlci == NULL)
3081 		return;
3082 	if (dlci->state == DLCI_CLOSED)
3083 		return;
3084 	mutex_lock(&dlci->mutex);
3085 	gsm_destroy_network(dlci);
3086 	mutex_unlock(&dlci->mutex);
3087 	if (tty_port_close_start(&dlci->port, tty, filp) == 0)
3088 		return;
3089 	gsm_dlci_begin_close(dlci);
3090 	if (tty_port_initialized(&dlci->port) && C_HUPCL(tty))
3091 		tty_port_lower_dtr_rts(&dlci->port);
3092 	tty_port_close_end(&dlci->port, tty);
3093 	tty_port_tty_set(&dlci->port, NULL);
3094 	return;
3095 }
3096 
3097 static void gsmtty_hangup(struct tty_struct *tty)
3098 {
3099 	struct gsm_dlci *dlci = tty->driver_data;
3100 	if (dlci->state == DLCI_CLOSED)
3101 		return;
3102 	tty_port_hangup(&dlci->port);
3103 	gsm_dlci_begin_close(dlci);
3104 }
3105 
3106 static int gsmtty_write(struct tty_struct *tty, const unsigned char *buf,
3107 								    int len)
3108 {
3109 	int sent;
3110 	struct gsm_dlci *dlci = tty->driver_data;
3111 	if (dlci->state == DLCI_CLOSED)
3112 		return -EINVAL;
3113 	/* Stuff the bytes into the fifo queue */
3114 	sent = kfifo_in_locked(&dlci->fifo, buf, len, &dlci->lock);
3115 	/* Need to kick the channel */
3116 	gsm_dlci_data_kick(dlci);
3117 	return sent;
3118 }
3119 
3120 static unsigned int gsmtty_write_room(struct tty_struct *tty)
3121 {
3122 	struct gsm_dlci *dlci = tty->driver_data;
3123 	if (dlci->state == DLCI_CLOSED)
3124 		return 0;
3125 	return TX_SIZE - kfifo_len(&dlci->fifo);
3126 }
3127 
3128 static unsigned int gsmtty_chars_in_buffer(struct tty_struct *tty)
3129 {
3130 	struct gsm_dlci *dlci = tty->driver_data;
3131 	if (dlci->state == DLCI_CLOSED)
3132 		return 0;
3133 	return kfifo_len(&dlci->fifo);
3134 }
3135 
3136 static void gsmtty_flush_buffer(struct tty_struct *tty)
3137 {
3138 	struct gsm_dlci *dlci = tty->driver_data;
3139 	if (dlci->state == DLCI_CLOSED)
3140 		return;
3141 	/* Caution needed: If we implement reliable transport classes
3142 	   then the data being transmitted can't simply be junked once
3143 	   it has first hit the stack. Until then we can just blow it
3144 	   away */
3145 	kfifo_reset(&dlci->fifo);
3146 	/* Need to unhook this DLCI from the transmit queue logic */
3147 }
3148 
3149 static void gsmtty_wait_until_sent(struct tty_struct *tty, int timeout)
3150 {
3151 	/* The FIFO handles the queue so the kernel will do the right
3152 	   thing waiting on chars_in_buffer before calling us. No work
3153 	   to do here */
3154 }
3155 
3156 static int gsmtty_tiocmget(struct tty_struct *tty)
3157 {
3158 	struct gsm_dlci *dlci = tty->driver_data;
3159 	if (dlci->state == DLCI_CLOSED)
3160 		return -EINVAL;
3161 	return dlci->modem_rx;
3162 }
3163 
3164 static int gsmtty_tiocmset(struct tty_struct *tty,
3165 	unsigned int set, unsigned int clear)
3166 {
3167 	struct gsm_dlci *dlci = tty->driver_data;
3168 	unsigned int modem_tx = dlci->modem_tx;
3169 
3170 	if (dlci->state == DLCI_CLOSED)
3171 		return -EINVAL;
3172 	modem_tx &= ~clear;
3173 	modem_tx |= set;
3174 
3175 	if (modem_tx != dlci->modem_tx) {
3176 		dlci->modem_tx = modem_tx;
3177 		return gsmtty_modem_update(dlci, 0);
3178 	}
3179 	return 0;
3180 }
3181 
3182 
3183 static int gsmtty_ioctl(struct tty_struct *tty,
3184 			unsigned int cmd, unsigned long arg)
3185 {
3186 	struct gsm_dlci *dlci = tty->driver_data;
3187 	struct gsm_netconfig nc;
3188 	int index;
3189 
3190 	if (dlci->state == DLCI_CLOSED)
3191 		return -EINVAL;
3192 	switch (cmd) {
3193 	case GSMIOC_ENABLE_NET:
3194 		if (copy_from_user(&nc, (void __user *)arg, sizeof(nc)))
3195 			return -EFAULT;
3196 		nc.if_name[IFNAMSIZ-1] = '\0';
3197 		/* return net interface index or error code */
3198 		mutex_lock(&dlci->mutex);
3199 		index = gsm_create_network(dlci, &nc);
3200 		mutex_unlock(&dlci->mutex);
3201 		if (copy_to_user((void __user *)arg, &nc, sizeof(nc)))
3202 			return -EFAULT;
3203 		return index;
3204 	case GSMIOC_DISABLE_NET:
3205 		if (!capable(CAP_NET_ADMIN))
3206 			return -EPERM;
3207 		mutex_lock(&dlci->mutex);
3208 		gsm_destroy_network(dlci);
3209 		mutex_unlock(&dlci->mutex);
3210 		return 0;
3211 	default:
3212 		return -ENOIOCTLCMD;
3213 	}
3214 }
3215 
3216 static void gsmtty_set_termios(struct tty_struct *tty, struct ktermios *old)
3217 {
3218 	struct gsm_dlci *dlci = tty->driver_data;
3219 	if (dlci->state == DLCI_CLOSED)
3220 		return;
3221 	/* For the moment its fixed. In actual fact the speed information
3222 	   for the virtual channel can be propogated in both directions by
3223 	   the RPN control message. This however rapidly gets nasty as we
3224 	   then have to remap modem signals each way according to whether
3225 	   our virtual cable is null modem etc .. */
3226 	tty_termios_copy_hw(&tty->termios, old);
3227 }
3228 
3229 static void gsmtty_throttle(struct tty_struct *tty)
3230 {
3231 	struct gsm_dlci *dlci = tty->driver_data;
3232 	if (dlci->state == DLCI_CLOSED)
3233 		return;
3234 	if (C_CRTSCTS(tty))
3235 		dlci->modem_tx &= ~TIOCM_DTR;
3236 	dlci->throttled = true;
3237 	/* Send an MSC with DTR cleared */
3238 	gsmtty_modem_update(dlci, 0);
3239 }
3240 
3241 static void gsmtty_unthrottle(struct tty_struct *tty)
3242 {
3243 	struct gsm_dlci *dlci = tty->driver_data;
3244 	if (dlci->state == DLCI_CLOSED)
3245 		return;
3246 	if (C_CRTSCTS(tty))
3247 		dlci->modem_tx |= TIOCM_DTR;
3248 	dlci->throttled = false;
3249 	/* Send an MSC with DTR set */
3250 	gsmtty_modem_update(dlci, 0);
3251 }
3252 
3253 static int gsmtty_break_ctl(struct tty_struct *tty, int state)
3254 {
3255 	struct gsm_dlci *dlci = tty->driver_data;
3256 	int encode = 0;	/* Off */
3257 	if (dlci->state == DLCI_CLOSED)
3258 		return -EINVAL;
3259 
3260 	if (state == -1)	/* "On indefinitely" - we can't encode this
3261 				    properly */
3262 		encode = 0x0F;
3263 	else if (state > 0) {
3264 		encode = state / 200;	/* mS to encoding */
3265 		if (encode > 0x0F)
3266 			encode = 0x0F;	/* Best effort */
3267 	}
3268 	return gsmtty_modem_update(dlci, encode);
3269 }
3270 
3271 static void gsmtty_cleanup(struct tty_struct *tty)
3272 {
3273 	struct gsm_dlci *dlci = tty->driver_data;
3274 	struct gsm_mux *gsm = dlci->gsm;
3275 
3276 	dlci_put(dlci);
3277 	dlci_put(gsm->dlci[0]);
3278 	mux_put(gsm);
3279 }
3280 
3281 /* Virtual ttys for the demux */
3282 static const struct tty_operations gsmtty_ops = {
3283 	.install		= gsmtty_install,
3284 	.open			= gsmtty_open,
3285 	.close			= gsmtty_close,
3286 	.write			= gsmtty_write,
3287 	.write_room		= gsmtty_write_room,
3288 	.chars_in_buffer	= gsmtty_chars_in_buffer,
3289 	.flush_buffer		= gsmtty_flush_buffer,
3290 	.ioctl			= gsmtty_ioctl,
3291 	.throttle		= gsmtty_throttle,
3292 	.unthrottle		= gsmtty_unthrottle,
3293 	.set_termios		= gsmtty_set_termios,
3294 	.hangup			= gsmtty_hangup,
3295 	.wait_until_sent	= gsmtty_wait_until_sent,
3296 	.tiocmget		= gsmtty_tiocmget,
3297 	.tiocmset		= gsmtty_tiocmset,
3298 	.break_ctl		= gsmtty_break_ctl,
3299 	.cleanup		= gsmtty_cleanup,
3300 };
3301 
3302 
3303 
3304 static int __init gsm_init(void)
3305 {
3306 	/* Fill in our line protocol discipline, and register it */
3307 	int status = tty_register_ldisc(&tty_ldisc_packet);
3308 	if (status != 0) {
3309 		pr_err("n_gsm: can't register line discipline (err = %d)\n",
3310 								status);
3311 		return status;
3312 	}
3313 
3314 	gsm_tty_driver = tty_alloc_driver(256, TTY_DRIVER_REAL_RAW |
3315 			TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_HARDWARE_BREAK);
3316 	if (IS_ERR(gsm_tty_driver)) {
3317 		pr_err("gsm_init: tty allocation failed.\n");
3318 		status = PTR_ERR(gsm_tty_driver);
3319 		goto err_unreg_ldisc;
3320 	}
3321 	gsm_tty_driver->driver_name	= "gsmtty";
3322 	gsm_tty_driver->name		= "gsmtty";
3323 	gsm_tty_driver->major		= 0;	/* Dynamic */
3324 	gsm_tty_driver->minor_start	= 0;
3325 	gsm_tty_driver->type		= TTY_DRIVER_TYPE_SERIAL;
3326 	gsm_tty_driver->subtype	= SERIAL_TYPE_NORMAL;
3327 	gsm_tty_driver->init_termios	= tty_std_termios;
3328 	/* Fixme */
3329 	gsm_tty_driver->init_termios.c_lflag &= ~ECHO;
3330 	tty_set_operations(gsm_tty_driver, &gsmtty_ops);
3331 
3332 	if (tty_register_driver(gsm_tty_driver)) {
3333 		pr_err("gsm_init: tty registration failed.\n");
3334 		status = -EBUSY;
3335 		goto err_put_driver;
3336 	}
3337 	pr_debug("gsm_init: loaded as %d,%d.\n",
3338 			gsm_tty_driver->major, gsm_tty_driver->minor_start);
3339 	return 0;
3340 err_put_driver:
3341 	tty_driver_kref_put(gsm_tty_driver);
3342 err_unreg_ldisc:
3343 	tty_unregister_ldisc(&tty_ldisc_packet);
3344 	return status;
3345 }
3346 
3347 static void __exit gsm_exit(void)
3348 {
3349 	tty_unregister_ldisc(&tty_ldisc_packet);
3350 	tty_unregister_driver(gsm_tty_driver);
3351 	tty_driver_kref_put(gsm_tty_driver);
3352 }
3353 
3354 module_init(gsm_init);
3355 module_exit(gsm_exit);
3356 
3357 
3358 MODULE_LICENSE("GPL");
3359 MODULE_ALIAS_LDISC(N_GSM0710);
3360