xref: /openbmc/linux/drivers/usb/serial/ch341.c (revision 5a158981)
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
4  * Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
5  * Copyright 2009, Boris Hajduk <boris@hajduk.org>
6  *
7  * ch341.c implements a serial port driver for the Winchiphead CH341.
8  *
9  * The CH341 device can be used to implement an RS232 asynchronous
10  * serial port, an IEEE-1284 parallel printer port or a memory-like
11  * interface. In all cases the CH341 supports an I2C interface as well.
12  * This driver only supports the asynchronous serial interface.
13  */
14 
15 #include <linux/kernel.h>
16 #include <linux/tty.h>
17 #include <linux/module.h>
18 #include <linux/slab.h>
19 #include <linux/usb.h>
20 #include <linux/usb/serial.h>
21 #include <linux/serial.h>
22 #include <asm/unaligned.h>
23 
24 #define DEFAULT_BAUD_RATE 9600
25 #define DEFAULT_TIMEOUT   1000
26 
27 /* flags for IO-Bits */
28 #define CH341_BIT_RTS (1 << 6)
29 #define CH341_BIT_DTR (1 << 5)
30 
31 /******************************/
32 /* interrupt pipe definitions */
33 /******************************/
34 /* always 4 interrupt bytes */
35 /* first irq byte normally 0x08 */
36 /* second irq byte base 0x7d + below */
37 /* third irq byte base 0x94 + below */
38 /* fourth irq byte normally 0xee */
39 
40 /* second interrupt byte */
41 #define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */
42 
43 /* status returned in third interrupt answer byte, inverted in data
44    from irq */
45 #define CH341_BIT_CTS 0x01
46 #define CH341_BIT_DSR 0x02
47 #define CH341_BIT_RI  0x04
48 #define CH341_BIT_DCD 0x08
49 #define CH341_BITS_MODEM_STAT 0x0f /* all bits */
50 
51 /* Break support - the information used to implement this was gleaned from
52  * the Net/FreeBSD uchcom.c driver by Takanori Watanabe.  Domo arigato.
53  */
54 
55 #define CH341_REQ_READ_VERSION 0x5F
56 #define CH341_REQ_WRITE_REG    0x9A
57 #define CH341_REQ_READ_REG     0x95
58 #define CH341_REQ_SERIAL_INIT  0xA1
59 #define CH341_REQ_MODEM_CTRL   0xA4
60 
61 #define CH341_REG_BREAK        0x05
62 #define CH341_REG_LCR          0x18
63 #define CH341_NBREAK_BITS      0x01
64 
65 #define CH341_LCR_ENABLE_RX    0x80
66 #define CH341_LCR_ENABLE_TX    0x40
67 #define CH341_LCR_MARK_SPACE   0x20
68 #define CH341_LCR_PAR_EVEN     0x10
69 #define CH341_LCR_ENABLE_PAR   0x08
70 #define CH341_LCR_STOP_BITS_2  0x04
71 #define CH341_LCR_CS8          0x03
72 #define CH341_LCR_CS7          0x02
73 #define CH341_LCR_CS6          0x01
74 #define CH341_LCR_CS5          0x00
75 
76 static const struct usb_device_id id_table[] = {
77 	{ USB_DEVICE(0x4348, 0x5523) },
78 	{ USB_DEVICE(0x1a86, 0x7523) },
79 	{ USB_DEVICE(0x1a86, 0x5523) },
80 	{ },
81 };
82 MODULE_DEVICE_TABLE(usb, id_table);
83 
84 struct ch341_private {
85 	spinlock_t lock; /* access lock */
86 	unsigned baud_rate; /* set baud rate */
87 	u8 mcr;
88 	u8 msr;
89 	u8 lcr;
90 };
91 
92 static void ch341_set_termios(struct tty_struct *tty,
93 			      struct usb_serial_port *port,
94 			      struct ktermios *old_termios);
95 
96 static int ch341_control_out(struct usb_device *dev, u8 request,
97 			     u16 value, u16 index)
98 {
99 	int r;
100 
101 	dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__,
102 		request, value, index);
103 
104 	r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
105 			    USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
106 			    value, index, NULL, 0, DEFAULT_TIMEOUT);
107 	if (r < 0)
108 		dev_err(&dev->dev, "failed to send control message: %d\n", r);
109 
110 	return r;
111 }
112 
113 static int ch341_control_in(struct usb_device *dev,
114 			    u8 request, u16 value, u16 index,
115 			    char *buf, unsigned bufsize)
116 {
117 	int r;
118 
119 	dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
120 		request, value, index, bufsize);
121 
122 	r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
123 			    USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
124 			    value, index, buf, bufsize, DEFAULT_TIMEOUT);
125 	if (r < (int)bufsize) {
126 		if (r >= 0) {
127 			dev_err(&dev->dev,
128 				"short control message received (%d < %u)\n",
129 				r, bufsize);
130 			r = -EIO;
131 		}
132 
133 		dev_err(&dev->dev, "failed to receive control message: %d\n",
134 			r);
135 		return r;
136 	}
137 
138 	return 0;
139 }
140 
141 #define CH341_CLKRATE		48000000
142 #define CH341_CLK_DIV(ps, fact)	(1 << (12 - 3 * (ps) - (fact)))
143 #define CH341_MIN_RATE(ps)	(CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512))
144 
145 static const speed_t ch341_min_rates[] = {
146 	CH341_MIN_RATE(0),
147 	CH341_MIN_RATE(1),
148 	CH341_MIN_RATE(2),
149 	CH341_MIN_RATE(3),
150 };
151 
152 /*
153  * The device line speed is given by the following equation:
154  *
155  *	baudrate = 48000000 / (2^(12 - 3 * ps - fact) * div), where
156  *
157  *		0 <= ps <= 3,
158  *		0 <= fact <= 1,
159  *		2 <= div <= 256 if fact = 0, or
160  *		9 <= div <= 256 if fact = 1
161  */
162 static int ch341_get_divisor(speed_t speed)
163 {
164 	unsigned int fact, div, clk_div;
165 	int ps;
166 
167 	/*
168 	 * Clamp to supported range, this makes the (ps < 0) and (div < 2)
169 	 * sanity checks below redundant.
170 	 */
171 	speed = clamp(speed, 46U, 3000000U);
172 
173 	/*
174 	 * Start with highest possible base clock (fact = 1) that will give a
175 	 * divisor strictly less than 512.
176 	 */
177 	fact = 1;
178 	for (ps = 3; ps >= 0; ps--) {
179 		if (speed > ch341_min_rates[ps])
180 			break;
181 	}
182 
183 	if (ps < 0)
184 		return -EINVAL;
185 
186 	/* Determine corresponding divisor, rounding down. */
187 	clk_div = CH341_CLK_DIV(ps, fact);
188 	div = CH341_CLKRATE / (clk_div * speed);
189 
190 	/* Halve base clock (fact = 0) if required. */
191 	if (div < 9 || div > 255) {
192 		div /= 2;
193 		clk_div *= 2;
194 		fact = 0;
195 	}
196 
197 	if (div < 2)
198 		return -EINVAL;
199 
200 	/*
201 	 * Pick next divisor if resulting rate is closer to the requested one,
202 	 * scale up to avoid rounding errors on low rates.
203 	 */
204 	if (16 * CH341_CLKRATE / (clk_div * div) - 16 * speed >=
205 			16 * speed - 16 * CH341_CLKRATE / (clk_div * (div + 1)))
206 		div++;
207 
208 	return (0x100 - div) << 8 | fact << 2 | ps;
209 }
210 
211 static int ch341_set_baudrate_lcr(struct usb_device *dev,
212 				  struct ch341_private *priv, u8 lcr)
213 {
214 	int val;
215 	int r;
216 
217 	if (!priv->baud_rate)
218 		return -EINVAL;
219 
220 	val = ch341_get_divisor(priv->baud_rate);
221 	if (val < 0)
222 		return -EINVAL;
223 
224 	/*
225 	 * CH341A buffers data until a full endpoint-size packet (32 bytes)
226 	 * has been received unless bit 7 is set.
227 	 */
228 	val |= BIT(7);
229 
230 	r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x1312, val);
231 	if (r)
232 		return r;
233 
234 	r = ch341_control_out(dev, CH341_REQ_WRITE_REG, 0x2518, lcr);
235 	if (r)
236 		return r;
237 
238 	return r;
239 }
240 
241 static int ch341_set_handshake(struct usb_device *dev, u8 control)
242 {
243 	return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0);
244 }
245 
246 static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
247 {
248 	const unsigned int size = 2;
249 	char *buffer;
250 	int r;
251 	unsigned long flags;
252 
253 	buffer = kmalloc(size, GFP_KERNEL);
254 	if (!buffer)
255 		return -ENOMEM;
256 
257 	r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
258 	if (r < 0)
259 		goto out;
260 
261 	spin_lock_irqsave(&priv->lock, flags);
262 	priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
263 	spin_unlock_irqrestore(&priv->lock, flags);
264 
265 out:	kfree(buffer);
266 	return r;
267 }
268 
269 /* -------------------------------------------------------------------------- */
270 
271 static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
272 {
273 	const unsigned int size = 2;
274 	char *buffer;
275 	int r;
276 
277 	buffer = kmalloc(size, GFP_KERNEL);
278 	if (!buffer)
279 		return -ENOMEM;
280 
281 	/* expect two bytes 0x27 0x00 */
282 	r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
283 	if (r < 0)
284 		goto out;
285 	dev_dbg(&dev->dev, "Chip version: 0x%02x\n", buffer[0]);
286 
287 	r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
288 	if (r < 0)
289 		goto out;
290 
291 	r = ch341_set_baudrate_lcr(dev, priv, priv->lcr);
292 	if (r < 0)
293 		goto out;
294 
295 	r = ch341_set_handshake(dev, priv->mcr);
296 
297 out:	kfree(buffer);
298 	return r;
299 }
300 
301 static int ch341_port_probe(struct usb_serial_port *port)
302 {
303 	struct ch341_private *priv;
304 	int r;
305 
306 	priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
307 	if (!priv)
308 		return -ENOMEM;
309 
310 	spin_lock_init(&priv->lock);
311 	priv->baud_rate = DEFAULT_BAUD_RATE;
312 	/*
313 	 * Some CH340 devices appear unable to change the initial LCR
314 	 * settings, so set a sane 8N1 default.
315 	 */
316 	priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
317 
318 	r = ch341_configure(port->serial->dev, priv);
319 	if (r < 0)
320 		goto error;
321 
322 	usb_set_serial_port_data(port, priv);
323 	return 0;
324 
325 error:	kfree(priv);
326 	return r;
327 }
328 
329 static int ch341_port_remove(struct usb_serial_port *port)
330 {
331 	struct ch341_private *priv;
332 
333 	priv = usb_get_serial_port_data(port);
334 	kfree(priv);
335 
336 	return 0;
337 }
338 
339 static int ch341_carrier_raised(struct usb_serial_port *port)
340 {
341 	struct ch341_private *priv = usb_get_serial_port_data(port);
342 	if (priv->msr & CH341_BIT_DCD)
343 		return 1;
344 	return 0;
345 }
346 
347 static void ch341_dtr_rts(struct usb_serial_port *port, int on)
348 {
349 	struct ch341_private *priv = usb_get_serial_port_data(port);
350 	unsigned long flags;
351 
352 	/* drop DTR and RTS */
353 	spin_lock_irqsave(&priv->lock, flags);
354 	if (on)
355 		priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
356 	else
357 		priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
358 	spin_unlock_irqrestore(&priv->lock, flags);
359 	ch341_set_handshake(port->serial->dev, priv->mcr);
360 }
361 
362 static void ch341_close(struct usb_serial_port *port)
363 {
364 	usb_serial_generic_close(port);
365 	usb_kill_urb(port->interrupt_in_urb);
366 }
367 
368 
369 /* open this device, set default parameters */
370 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
371 {
372 	struct ch341_private *priv = usb_get_serial_port_data(port);
373 	int r;
374 
375 	if (tty)
376 		ch341_set_termios(tty, port, NULL);
377 
378 	dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
379 	r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
380 	if (r) {
381 		dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n",
382 			__func__, r);
383 		return r;
384 	}
385 
386 	r = ch341_get_status(port->serial->dev, priv);
387 	if (r < 0) {
388 		dev_err(&port->dev, "failed to read modem status: %d\n", r);
389 		goto err_kill_interrupt_urb;
390 	}
391 
392 	r = usb_serial_generic_open(tty, port);
393 	if (r)
394 		goto err_kill_interrupt_urb;
395 
396 	return 0;
397 
398 err_kill_interrupt_urb:
399 	usb_kill_urb(port->interrupt_in_urb);
400 
401 	return r;
402 }
403 
404 /* Old_termios contains the original termios settings and
405  * tty->termios contains the new setting to be used.
406  */
407 static void ch341_set_termios(struct tty_struct *tty,
408 		struct usb_serial_port *port, struct ktermios *old_termios)
409 {
410 	struct ch341_private *priv = usb_get_serial_port_data(port);
411 	unsigned baud_rate;
412 	unsigned long flags;
413 	u8 lcr;
414 	int r;
415 
416 	/* redundant changes may cause the chip to lose bytes */
417 	if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
418 		return;
419 
420 	baud_rate = tty_get_baud_rate(tty);
421 
422 	lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
423 
424 	switch (C_CSIZE(tty)) {
425 	case CS5:
426 		lcr |= CH341_LCR_CS5;
427 		break;
428 	case CS6:
429 		lcr |= CH341_LCR_CS6;
430 		break;
431 	case CS7:
432 		lcr |= CH341_LCR_CS7;
433 		break;
434 	case CS8:
435 		lcr |= CH341_LCR_CS8;
436 		break;
437 	}
438 
439 	if (C_PARENB(tty)) {
440 		lcr |= CH341_LCR_ENABLE_PAR;
441 		if (C_PARODD(tty) == 0)
442 			lcr |= CH341_LCR_PAR_EVEN;
443 		if (C_CMSPAR(tty))
444 			lcr |= CH341_LCR_MARK_SPACE;
445 	}
446 
447 	if (C_CSTOPB(tty))
448 		lcr |= CH341_LCR_STOP_BITS_2;
449 
450 	if (baud_rate) {
451 		priv->baud_rate = baud_rate;
452 
453 		r = ch341_set_baudrate_lcr(port->serial->dev, priv, lcr);
454 		if (r < 0 && old_termios) {
455 			priv->baud_rate = tty_termios_baud_rate(old_termios);
456 			tty_termios_copy_hw(&tty->termios, old_termios);
457 		} else if (r == 0) {
458 			priv->lcr = lcr;
459 		}
460 	}
461 
462 	spin_lock_irqsave(&priv->lock, flags);
463 	if (C_BAUD(tty) == B0)
464 		priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
465 	else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
466 		priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
467 	spin_unlock_irqrestore(&priv->lock, flags);
468 
469 	ch341_set_handshake(port->serial->dev, priv->mcr);
470 }
471 
472 static void ch341_break_ctl(struct tty_struct *tty, int break_state)
473 {
474 	const uint16_t ch341_break_reg =
475 			((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK;
476 	struct usb_serial_port *port = tty->driver_data;
477 	int r;
478 	uint16_t reg_contents;
479 	uint8_t *break_reg;
480 
481 	break_reg = kmalloc(2, GFP_KERNEL);
482 	if (!break_reg)
483 		return;
484 
485 	r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
486 			ch341_break_reg, 0, break_reg, 2);
487 	if (r < 0) {
488 		dev_err(&port->dev, "%s - USB control read error (%d)\n",
489 				__func__, r);
490 		goto out;
491 	}
492 	dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
493 		__func__, break_reg[0], break_reg[1]);
494 	if (break_state != 0) {
495 		dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
496 		break_reg[0] &= ~CH341_NBREAK_BITS;
497 		break_reg[1] &= ~CH341_LCR_ENABLE_TX;
498 	} else {
499 		dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
500 		break_reg[0] |= CH341_NBREAK_BITS;
501 		break_reg[1] |= CH341_LCR_ENABLE_TX;
502 	}
503 	dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
504 		__func__, break_reg[0], break_reg[1]);
505 	reg_contents = get_unaligned_le16(break_reg);
506 	r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
507 			ch341_break_reg, reg_contents);
508 	if (r < 0)
509 		dev_err(&port->dev, "%s - USB control write error (%d)\n",
510 				__func__, r);
511 out:
512 	kfree(break_reg);
513 }
514 
515 static int ch341_tiocmset(struct tty_struct *tty,
516 			  unsigned int set, unsigned int clear)
517 {
518 	struct usb_serial_port *port = tty->driver_data;
519 	struct ch341_private *priv = usb_get_serial_port_data(port);
520 	unsigned long flags;
521 	u8 control;
522 
523 	spin_lock_irqsave(&priv->lock, flags);
524 	if (set & TIOCM_RTS)
525 		priv->mcr |= CH341_BIT_RTS;
526 	if (set & TIOCM_DTR)
527 		priv->mcr |= CH341_BIT_DTR;
528 	if (clear & TIOCM_RTS)
529 		priv->mcr &= ~CH341_BIT_RTS;
530 	if (clear & TIOCM_DTR)
531 		priv->mcr &= ~CH341_BIT_DTR;
532 	control = priv->mcr;
533 	spin_unlock_irqrestore(&priv->lock, flags);
534 
535 	return ch341_set_handshake(port->serial->dev, control);
536 }
537 
538 static void ch341_update_status(struct usb_serial_port *port,
539 					unsigned char *data, size_t len)
540 {
541 	struct ch341_private *priv = usb_get_serial_port_data(port);
542 	struct tty_struct *tty;
543 	unsigned long flags;
544 	u8 status;
545 	u8 delta;
546 
547 	if (len < 4)
548 		return;
549 
550 	status = ~data[2] & CH341_BITS_MODEM_STAT;
551 
552 	spin_lock_irqsave(&priv->lock, flags);
553 	delta = status ^ priv->msr;
554 	priv->msr = status;
555 	spin_unlock_irqrestore(&priv->lock, flags);
556 
557 	if (data[1] & CH341_MULT_STAT)
558 		dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
559 
560 	if (!delta)
561 		return;
562 
563 	if (delta & CH341_BIT_CTS)
564 		port->icount.cts++;
565 	if (delta & CH341_BIT_DSR)
566 		port->icount.dsr++;
567 	if (delta & CH341_BIT_RI)
568 		port->icount.rng++;
569 	if (delta & CH341_BIT_DCD) {
570 		port->icount.dcd++;
571 		tty = tty_port_tty_get(&port->port);
572 		if (tty) {
573 			usb_serial_handle_dcd_change(port, tty,
574 						status & CH341_BIT_DCD);
575 			tty_kref_put(tty);
576 		}
577 	}
578 
579 	wake_up_interruptible(&port->port.delta_msr_wait);
580 }
581 
582 static void ch341_read_int_callback(struct urb *urb)
583 {
584 	struct usb_serial_port *port = urb->context;
585 	unsigned char *data = urb->transfer_buffer;
586 	unsigned int len = urb->actual_length;
587 	int status;
588 
589 	switch (urb->status) {
590 	case 0:
591 		/* success */
592 		break;
593 	case -ECONNRESET:
594 	case -ENOENT:
595 	case -ESHUTDOWN:
596 		/* this urb is terminated, clean up */
597 		dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n",
598 			__func__, urb->status);
599 		return;
600 	default:
601 		dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n",
602 			__func__, urb->status);
603 		goto exit;
604 	}
605 
606 	usb_serial_debug_data(&port->dev, __func__, len, data);
607 	ch341_update_status(port, data, len);
608 exit:
609 	status = usb_submit_urb(urb, GFP_ATOMIC);
610 	if (status) {
611 		dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n",
612 			__func__, status);
613 	}
614 }
615 
616 static int ch341_tiocmget(struct tty_struct *tty)
617 {
618 	struct usb_serial_port *port = tty->driver_data;
619 	struct ch341_private *priv = usb_get_serial_port_data(port);
620 	unsigned long flags;
621 	u8 mcr;
622 	u8 status;
623 	unsigned int result;
624 
625 	spin_lock_irqsave(&priv->lock, flags);
626 	mcr = priv->mcr;
627 	status = priv->msr;
628 	spin_unlock_irqrestore(&priv->lock, flags);
629 
630 	result = ((mcr & CH341_BIT_DTR)		? TIOCM_DTR : 0)
631 		  | ((mcr & CH341_BIT_RTS)	? TIOCM_RTS : 0)
632 		  | ((status & CH341_BIT_CTS)	? TIOCM_CTS : 0)
633 		  | ((status & CH341_BIT_DSR)	? TIOCM_DSR : 0)
634 		  | ((status & CH341_BIT_RI)	? TIOCM_RI  : 0)
635 		  | ((status & CH341_BIT_DCD)	? TIOCM_CD  : 0);
636 
637 	dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
638 
639 	return result;
640 }
641 
642 static int ch341_reset_resume(struct usb_serial *serial)
643 {
644 	struct usb_serial_port *port = serial->port[0];
645 	struct ch341_private *priv = usb_get_serial_port_data(port);
646 	int ret;
647 
648 	/* reconfigure ch341 serial port after bus-reset */
649 	ch341_configure(serial->dev, priv);
650 
651 	if (tty_port_initialized(&port->port)) {
652 		ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
653 		if (ret) {
654 			dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
655 				ret);
656 			return ret;
657 		}
658 
659 		ret = ch341_get_status(port->serial->dev, priv);
660 		if (ret < 0) {
661 			dev_err(&port->dev, "failed to read modem status: %d\n",
662 				ret);
663 		}
664 	}
665 
666 	return usb_serial_generic_resume(serial);
667 }
668 
669 static struct usb_serial_driver ch341_device = {
670 	.driver = {
671 		.owner	= THIS_MODULE,
672 		.name	= "ch341-uart",
673 	},
674 	.id_table          = id_table,
675 	.num_ports         = 1,
676 	.open              = ch341_open,
677 	.dtr_rts	   = ch341_dtr_rts,
678 	.carrier_raised	   = ch341_carrier_raised,
679 	.close             = ch341_close,
680 	.set_termios       = ch341_set_termios,
681 	.break_ctl         = ch341_break_ctl,
682 	.tiocmget          = ch341_tiocmget,
683 	.tiocmset          = ch341_tiocmset,
684 	.tiocmiwait        = usb_serial_generic_tiocmiwait,
685 	.read_int_callback = ch341_read_int_callback,
686 	.port_probe        = ch341_port_probe,
687 	.port_remove       = ch341_port_remove,
688 	.reset_resume      = ch341_reset_resume,
689 };
690 
691 static struct usb_serial_driver * const serial_drivers[] = {
692 	&ch341_device, NULL
693 };
694 
695 module_usb_serial_driver(serial_drivers, id_table);
696 
697 MODULE_LICENSE("GPL v2");
698