1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * f_subset.c -- "CDC Subset" Ethernet link function driver
4  *
5  * Copyright (C) 2003-2005,2008 David Brownell
6  * Copyright (C) 2008 Nokia Corporation
7  */
8 
9 #include <linux/slab.h>
10 #include <linux/kernel.h>
11 #include <linux/module.h>
12 #include <linux/device.h>
13 #include <linux/etherdevice.h>
14 
15 #include "u_ether.h"
16 #include "u_ether_configfs.h"
17 #include "u_gether.h"
18 
19 /*
20  * This function packages a simple "CDC Subset" Ethernet port with no real
21  * control mechanisms; just raw data transfer over two bulk endpoints.
22  * The data transfer model is exactly that of CDC Ethernet, which is
23  * why we call it the "CDC Subset".
24  *
25  * Because it's not standardized, this has some interoperability issues.
26  * They mostly relate to driver binding, since the data transfer model is
27  * so simple (CDC Ethernet).  The original versions of this protocol used
28  * specific product/vendor IDs:  byteswapped IDs for Digital Equipment's
29  * SA-1100 "Itsy" board, which could run Linux 2.4 kernels and supported
30  * daughtercards with USB peripheral connectors.  (It was used more often
31  * with other boards, using the Itsy identifiers.)  Linux hosts recognized
32  * this with CONFIG_USB_ARMLINUX; these devices have only one configuration
33  * and one interface.
34  *
35  * At some point, MCCI defined a (nonconformant) CDC MDLM variant called
36  * "SAFE", which happens to have a mode which is identical to the "CDC
37  * Subset" in terms of data transfer and lack of control model.  This was
38  * adopted by later Sharp Zaurus models, and by some other software which
39  * Linux hosts recognize with CONFIG_USB_NET_ZAURUS.
40  *
41  * Because Microsoft's RNDIS drivers are far from robust, we added a few
42  * descriptors to the CDC Subset code, making this code look like a SAFE
43  * implementation.  This lets you use MCCI's host side MS-Windows drivers
44  * if you get fed up with RNDIS.  It also makes it easier for composite
45  * drivers to work, since they can use class based binding instead of
46  * caring about specific product and vendor IDs.
47  */
48 
49 struct f_gether {
50 	struct gether			port;
51 
52 	char				ethaddr[14];
53 };
54 
55 static inline struct f_gether *func_to_geth(struct usb_function *f)
56 {
57 	return container_of(f, struct f_gether, port.func);
58 }
59 
60 /*-------------------------------------------------------------------------*/
61 
62 /*
63  * "Simple" CDC-subset option is a simple vendor-neutral model that most
64  * full speed controllers can handle:  one interface, two bulk endpoints.
65  * To assist host side drivers, we fancy it up a bit, and add descriptors so
66  * some host side drivers will understand it as a "SAFE" variant.
67  *
68  * "SAFE" loosely follows CDC WMC MDLM, violating the spec in various ways.
69  * Data endpoints live in the control interface, there's no data interface.
70  * And it's not used to talk to a cell phone radio.
71  */
72 
73 /* interface descriptor: */
74 
75 static struct usb_interface_descriptor subset_data_intf = {
76 	.bLength =		sizeof subset_data_intf,
77 	.bDescriptorType =	USB_DT_INTERFACE,
78 
79 	/* .bInterfaceNumber = DYNAMIC */
80 	.bAlternateSetting =	0,
81 	.bNumEndpoints =	2,
82 	.bInterfaceClass =      USB_CLASS_COMM,
83 	.bInterfaceSubClass =	USB_CDC_SUBCLASS_MDLM,
84 	.bInterfaceProtocol =	0,
85 	/* .iInterface = DYNAMIC */
86 };
87 
88 static struct usb_cdc_header_desc mdlm_header_desc = {
89 	.bLength =		sizeof mdlm_header_desc,
90 	.bDescriptorType =	USB_DT_CS_INTERFACE,
91 	.bDescriptorSubType =	USB_CDC_HEADER_TYPE,
92 
93 	.bcdCDC =		cpu_to_le16(0x0110),
94 };
95 
96 static struct usb_cdc_mdlm_desc mdlm_desc = {
97 	.bLength =		sizeof mdlm_desc,
98 	.bDescriptorType =	USB_DT_CS_INTERFACE,
99 	.bDescriptorSubType =	USB_CDC_MDLM_TYPE,
100 
101 	.bcdVersion =		cpu_to_le16(0x0100),
102 	.bGUID = {
103 		0x5d, 0x34, 0xcf, 0x66, 0x11, 0x18, 0x11, 0xd6,
104 		0xa2, 0x1a, 0x00, 0x01, 0x02, 0xca, 0x9a, 0x7f,
105 	},
106 };
107 
108 /* since "usb_cdc_mdlm_detail_desc" is a variable length structure, we
109  * can't really use its struct.  All we do here is say that we're using
110  * the submode of "SAFE" which directly matches the CDC Subset.
111  */
112 static u8 mdlm_detail_desc[] = {
113 	6,
114 	USB_DT_CS_INTERFACE,
115 	USB_CDC_MDLM_DETAIL_TYPE,
116 
117 	0,	/* "SAFE" */
118 	0,	/* network control capabilities (none) */
119 	0,	/* network data capabilities ("raw" encapsulation) */
120 };
121 
122 static struct usb_cdc_ether_desc ether_desc = {
123 	.bLength =		sizeof ether_desc,
124 	.bDescriptorType =	USB_DT_CS_INTERFACE,
125 	.bDescriptorSubType =	USB_CDC_ETHERNET_TYPE,
126 
127 	/* this descriptor actually adds value, surprise! */
128 	/* .iMACAddress = DYNAMIC */
129 	.bmEthernetStatistics =	cpu_to_le32(0), /* no statistics */
130 	.wMaxSegmentSize =	cpu_to_le16(ETH_FRAME_LEN),
131 	.wNumberMCFilters =	cpu_to_le16(0),
132 	.bNumberPowerFilters =	0,
133 };
134 
135 /* full speed support: */
136 
137 static struct usb_endpoint_descriptor fs_subset_in_desc = {
138 	.bLength =		USB_DT_ENDPOINT_SIZE,
139 	.bDescriptorType =	USB_DT_ENDPOINT,
140 
141 	.bEndpointAddress =	USB_DIR_IN,
142 	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
143 };
144 
145 static struct usb_endpoint_descriptor fs_subset_out_desc = {
146 	.bLength =		USB_DT_ENDPOINT_SIZE,
147 	.bDescriptorType =	USB_DT_ENDPOINT,
148 
149 	.bEndpointAddress =	USB_DIR_OUT,
150 	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
151 };
152 
153 static struct usb_descriptor_header *fs_eth_function[] = {
154 	(struct usb_descriptor_header *) &subset_data_intf,
155 	(struct usb_descriptor_header *) &mdlm_header_desc,
156 	(struct usb_descriptor_header *) &mdlm_desc,
157 	(struct usb_descriptor_header *) &mdlm_detail_desc,
158 	(struct usb_descriptor_header *) &ether_desc,
159 	(struct usb_descriptor_header *) &fs_subset_in_desc,
160 	(struct usb_descriptor_header *) &fs_subset_out_desc,
161 	NULL,
162 };
163 
164 /* high speed support: */
165 
166 static struct usb_endpoint_descriptor hs_subset_in_desc = {
167 	.bLength =		USB_DT_ENDPOINT_SIZE,
168 	.bDescriptorType =	USB_DT_ENDPOINT,
169 
170 	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
171 	.wMaxPacketSize =	cpu_to_le16(512),
172 };
173 
174 static struct usb_endpoint_descriptor hs_subset_out_desc = {
175 	.bLength =		USB_DT_ENDPOINT_SIZE,
176 	.bDescriptorType =	USB_DT_ENDPOINT,
177 
178 	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
179 	.wMaxPacketSize =	cpu_to_le16(512),
180 };
181 
182 static struct usb_descriptor_header *hs_eth_function[] = {
183 	(struct usb_descriptor_header *) &subset_data_intf,
184 	(struct usb_descriptor_header *) &mdlm_header_desc,
185 	(struct usb_descriptor_header *) &mdlm_desc,
186 	(struct usb_descriptor_header *) &mdlm_detail_desc,
187 	(struct usb_descriptor_header *) &ether_desc,
188 	(struct usb_descriptor_header *) &hs_subset_in_desc,
189 	(struct usb_descriptor_header *) &hs_subset_out_desc,
190 	NULL,
191 };
192 
193 /* super speed support: */
194 
195 static struct usb_endpoint_descriptor ss_subset_in_desc = {
196 	.bLength =		USB_DT_ENDPOINT_SIZE,
197 	.bDescriptorType =	USB_DT_ENDPOINT,
198 
199 	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
200 	.wMaxPacketSize =	cpu_to_le16(1024),
201 };
202 
203 static struct usb_endpoint_descriptor ss_subset_out_desc = {
204 	.bLength =		USB_DT_ENDPOINT_SIZE,
205 	.bDescriptorType =	USB_DT_ENDPOINT,
206 
207 	.bmAttributes =		USB_ENDPOINT_XFER_BULK,
208 	.wMaxPacketSize =	cpu_to_le16(1024),
209 };
210 
211 static struct usb_ss_ep_comp_descriptor ss_subset_bulk_comp_desc = {
212 	.bLength =		sizeof ss_subset_bulk_comp_desc,
213 	.bDescriptorType =	USB_DT_SS_ENDPOINT_COMP,
214 
215 	/* the following 2 values can be tweaked if necessary */
216 	/* .bMaxBurst =		0, */
217 	/* .bmAttributes =	0, */
218 };
219 
220 static struct usb_descriptor_header *ss_eth_function[] = {
221 	(struct usb_descriptor_header *) &subset_data_intf,
222 	(struct usb_descriptor_header *) &mdlm_header_desc,
223 	(struct usb_descriptor_header *) &mdlm_desc,
224 	(struct usb_descriptor_header *) &mdlm_detail_desc,
225 	(struct usb_descriptor_header *) &ether_desc,
226 	(struct usb_descriptor_header *) &ss_subset_in_desc,
227 	(struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
228 	(struct usb_descriptor_header *) &ss_subset_out_desc,
229 	(struct usb_descriptor_header *) &ss_subset_bulk_comp_desc,
230 	NULL,
231 };
232 
233 /* string descriptors: */
234 
235 static struct usb_string geth_string_defs[] = {
236 	[0].s = "CDC Ethernet Subset/SAFE",
237 	[1].s = "",
238 	{  } /* end of list */
239 };
240 
241 static struct usb_gadget_strings geth_string_table = {
242 	.language =		0x0409,	/* en-us */
243 	.strings =		geth_string_defs,
244 };
245 
246 static struct usb_gadget_strings *geth_strings[] = {
247 	&geth_string_table,
248 	NULL,
249 };
250 
251 /*-------------------------------------------------------------------------*/
252 
253 static int geth_set_alt(struct usb_function *f, unsigned intf, unsigned alt)
254 {
255 	struct f_gether		*geth = func_to_geth(f);
256 	struct usb_composite_dev *cdev = f->config->cdev;
257 	struct net_device	*net;
258 
259 	/* we know alt == 0, so this is an activation or a reset */
260 
261 	if (geth->port.in_ep->enabled) {
262 		DBG(cdev, "reset cdc subset\n");
263 		gether_disconnect(&geth->port);
264 	}
265 
266 	DBG(cdev, "init + activate cdc subset\n");
267 	if (config_ep_by_speed(cdev->gadget, f, geth->port.in_ep) ||
268 	    config_ep_by_speed(cdev->gadget, f, geth->port.out_ep)) {
269 		geth->port.in_ep->desc = NULL;
270 		geth->port.out_ep->desc = NULL;
271 		return -EINVAL;
272 	}
273 
274 	net = gether_connect(&geth->port);
275 	return PTR_ERR_OR_ZERO(net);
276 }
277 
278 static void geth_disable(struct usb_function *f)
279 {
280 	struct f_gether	*geth = func_to_geth(f);
281 	struct usb_composite_dev *cdev = f->config->cdev;
282 
283 	DBG(cdev, "net deactivated\n");
284 	gether_disconnect(&geth->port);
285 }
286 
287 /*-------------------------------------------------------------------------*/
288 
289 /* serial function driver setup/binding */
290 
291 static int
292 geth_bind(struct usb_configuration *c, struct usb_function *f)
293 {
294 	struct usb_composite_dev *cdev = c->cdev;
295 	struct f_gether		*geth = func_to_geth(f);
296 	struct usb_string	*us;
297 	int			status;
298 	struct usb_ep		*ep;
299 
300 	struct f_gether_opts	*gether_opts;
301 
302 	gether_opts = container_of(f->fi, struct f_gether_opts, func_inst);
303 
304 	/*
305 	 * in drivers/usb/gadget/configfs.c:configfs_composite_bind()
306 	 * configurations are bound in sequence with list_for_each_entry,
307 	 * in each configuration its functions are bound in sequence
308 	 * with list_for_each_entry, so we assume no race condition
309 	 * with regard to gether_opts->bound access
310 	 */
311 	if (!gether_opts->bound) {
312 		mutex_lock(&gether_opts->lock);
313 		gether_set_gadget(gether_opts->net, cdev->gadget);
314 		status = gether_register_netdev(gether_opts->net);
315 		mutex_unlock(&gether_opts->lock);
316 		if (status)
317 			return status;
318 		gether_opts->bound = true;
319 	}
320 
321 	us = usb_gstrings_attach(cdev, geth_strings,
322 				 ARRAY_SIZE(geth_string_defs));
323 	if (IS_ERR(us))
324 		return PTR_ERR(us);
325 
326 	subset_data_intf.iInterface = us[0].id;
327 	ether_desc.iMACAddress = us[1].id;
328 
329 	/* allocate instance-specific interface IDs */
330 	status = usb_interface_id(c, f);
331 	if (status < 0)
332 		goto fail;
333 	subset_data_intf.bInterfaceNumber = status;
334 
335 	status = -ENODEV;
336 
337 	/* allocate instance-specific endpoints */
338 	ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_in_desc);
339 	if (!ep)
340 		goto fail;
341 	geth->port.in_ep = ep;
342 
343 	ep = usb_ep_autoconfig(cdev->gadget, &fs_subset_out_desc);
344 	if (!ep)
345 		goto fail;
346 	geth->port.out_ep = ep;
347 
348 	/* support all relevant hardware speeds... we expect that when
349 	 * hardware is dual speed, all bulk-capable endpoints work at
350 	 * both speeds
351 	 */
352 	hs_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
353 	hs_subset_out_desc.bEndpointAddress =
354 		fs_subset_out_desc.bEndpointAddress;
355 
356 	ss_subset_in_desc.bEndpointAddress = fs_subset_in_desc.bEndpointAddress;
357 	ss_subset_out_desc.bEndpointAddress =
358 		fs_subset_out_desc.bEndpointAddress;
359 
360 	status = usb_assign_descriptors(f, fs_eth_function, hs_eth_function,
361 			ss_eth_function, NULL);
362 	if (status)
363 		goto fail;
364 
365 	/* NOTE:  all that is done without knowing or caring about
366 	 * the network link ... which is unavailable to this code
367 	 * until we're activated via set_alt().
368 	 */
369 
370 	DBG(cdev, "CDC Subset: %s speed IN/%s OUT/%s\n",
371 			gadget_is_superspeed(c->cdev->gadget) ? "super" :
372 			gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
373 			geth->port.in_ep->name, geth->port.out_ep->name);
374 	return 0;
375 
376 fail:
377 	ERROR(cdev, "%s: can't bind, err %d\n", f->name, status);
378 
379 	return status;
380 }
381 
382 static inline struct f_gether_opts *to_f_gether_opts(struct config_item *item)
383 {
384 	return container_of(to_config_group(item), struct f_gether_opts,
385 			    func_inst.group);
386 }
387 
388 /* f_gether_item_ops */
389 USB_ETHERNET_CONFIGFS_ITEM(gether);
390 
391 /* f_gether_opts_dev_addr */
392 USB_ETHERNET_CONFIGFS_ITEM_ATTR_DEV_ADDR(gether);
393 
394 /* f_gether_opts_host_addr */
395 USB_ETHERNET_CONFIGFS_ITEM_ATTR_HOST_ADDR(gether);
396 
397 /* f_gether_opts_qmult */
398 USB_ETHERNET_CONFIGFS_ITEM_ATTR_QMULT(gether);
399 
400 /* f_gether_opts_ifname */
401 USB_ETHERNET_CONFIGFS_ITEM_ATTR_IFNAME(gether);
402 
403 static struct configfs_attribute *gether_attrs[] = {
404 	&gether_opts_attr_dev_addr,
405 	&gether_opts_attr_host_addr,
406 	&gether_opts_attr_qmult,
407 	&gether_opts_attr_ifname,
408 	NULL,
409 };
410 
411 static const struct config_item_type gether_func_type = {
412 	.ct_item_ops	= &gether_item_ops,
413 	.ct_attrs	= gether_attrs,
414 	.ct_owner	= THIS_MODULE,
415 };
416 
417 static void geth_free_inst(struct usb_function_instance *f)
418 {
419 	struct f_gether_opts *opts;
420 
421 	opts = container_of(f, struct f_gether_opts, func_inst);
422 	if (opts->bound)
423 		gether_cleanup(netdev_priv(opts->net));
424 	else
425 		free_netdev(opts->net);
426 	kfree(opts);
427 }
428 
429 static struct usb_function_instance *geth_alloc_inst(void)
430 {
431 	struct f_gether_opts *opts;
432 
433 	opts = kzalloc(sizeof(*opts), GFP_KERNEL);
434 	if (!opts)
435 		return ERR_PTR(-ENOMEM);
436 	mutex_init(&opts->lock);
437 	opts->func_inst.free_func_inst = geth_free_inst;
438 	opts->net = gether_setup_default();
439 	if (IS_ERR(opts->net)) {
440 		struct net_device *net = opts->net;
441 		kfree(opts);
442 		return ERR_CAST(net);
443 	}
444 
445 	config_group_init_type_name(&opts->func_inst.group, "",
446 				    &gether_func_type);
447 
448 	return &opts->func_inst;
449 }
450 
451 static void geth_free(struct usb_function *f)
452 {
453 	struct f_gether *eth;
454 
455 	eth = func_to_geth(f);
456 	kfree(eth);
457 }
458 
459 static void geth_unbind(struct usb_configuration *c, struct usb_function *f)
460 {
461 	geth_string_defs[0].id = 0;
462 	usb_free_all_descriptors(f);
463 }
464 
465 static struct usb_function *geth_alloc(struct usb_function_instance *fi)
466 {
467 	struct f_gether	*geth;
468 	struct f_gether_opts *opts;
469 	int status;
470 
471 	/* allocate and initialize one new instance */
472 	geth = kzalloc(sizeof(*geth), GFP_KERNEL);
473 	if (!geth)
474 		return ERR_PTR(-ENOMEM);
475 
476 	opts = container_of(fi, struct f_gether_opts, func_inst);
477 
478 	mutex_lock(&opts->lock);
479 	opts->refcnt++;
480 	/* export host's Ethernet address in CDC format */
481 	status = gether_get_host_addr_cdc(opts->net, geth->ethaddr,
482 					  sizeof(geth->ethaddr));
483 	if (status < 12) {
484 		kfree(geth);
485 		mutex_unlock(&opts->lock);
486 		return ERR_PTR(-EINVAL);
487 	}
488 	geth_string_defs[1].s = geth->ethaddr;
489 
490 	geth->port.ioport = netdev_priv(opts->net);
491 	mutex_unlock(&opts->lock);
492 	geth->port.cdc_filter = DEFAULT_FILTER;
493 
494 	geth->port.func.name = "cdc_subset";
495 	geth->port.func.bind = geth_bind;
496 	geth->port.func.unbind = geth_unbind;
497 	geth->port.func.set_alt = geth_set_alt;
498 	geth->port.func.disable = geth_disable;
499 	geth->port.func.free_func = geth_free;
500 
501 	return &geth->port.func;
502 }
503 
504 DECLARE_USB_FUNCTION_INIT(geth, geth_alloc_inst, geth_alloc);
505 MODULE_LICENSE("GPL");
506 MODULE_AUTHOR("David Brownell");
507