1 // SPDX-License-Identifier: GPL-2.0
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>
7 * ch341.c implements a serial port driver for the Winchiphead CH341.
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.
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>
24 #define DEFAULT_BAUD_RATE 9600
25 #define DEFAULT_TIMEOUT 1000
27 /* flags for IO-Bits */
28 #define CH341_BIT_RTS (1 << 6)
29 #define CH341_BIT_DTR (1 << 5)
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 */
40 /* second interrupt byte */
41 #define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */
43 /* status returned in third interrupt answer byte, inverted in data
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 */
51 /* Break support - the information used to implement this was gleaned from
52 * the Net/FreeBSD uchcom.c driver by Takanori Watanabe. Domo arigato.
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
61 #define CH341_REG_BREAK 0x05
62 #define CH341_REG_PRESCALER 0x12
63 #define CH341_REG_DIVISOR 0x13
64 #define CH341_REG_LCR 0x18
65 #define CH341_REG_LCR2 0x25
67 #define CH341_NBREAK_BITS 0x01
69 #define CH341_LCR_ENABLE_RX 0x80
70 #define CH341_LCR_ENABLE_TX 0x40
71 #define CH341_LCR_MARK_SPACE 0x20
72 #define CH341_LCR_PAR_EVEN 0x10
73 #define CH341_LCR_ENABLE_PAR 0x08
74 #define CH341_LCR_STOP_BITS_2 0x04
75 #define CH341_LCR_CS8 0x03
76 #define CH341_LCR_CS7 0x02
77 #define CH341_LCR_CS6 0x01
78 #define CH341_LCR_CS5 0x00
80 #define CH341_QUIRK_LIMITED_PRESCALER BIT(0)
81 #define CH341_QUIRK_SIMULATE_BREAK BIT(1)
83 static const struct usb_device_id id_table[] = {
84 { USB_DEVICE(0x1a86, 0x5523) },
85 { USB_DEVICE(0x1a86, 0x7522) },
86 { USB_DEVICE(0x1a86, 0x7523) },
87 { USB_DEVICE(0x2184, 0x0057) },
88 { USB_DEVICE(0x4348, 0x5523) },
89 { USB_DEVICE(0x9986, 0x7523) },
92 MODULE_DEVICE_TABLE(usb, id_table);
94 struct ch341_private {
95 spinlock_t lock; /* access lock */
96 unsigned baud_rate; /* set baud rate */
101 unsigned long quirks;
104 unsigned long break_end;
107 static void ch341_set_termios(struct tty_struct *tty,
108 struct usb_serial_port *port,
109 struct ktermios *old_termios);
111 static int ch341_control_out(struct usb_device *dev, u8 request,
112 u16 value, u16 index)
116 dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__,
117 request, value, index);
119 r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request,
120 USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
121 value, index, NULL, 0, DEFAULT_TIMEOUT);
123 dev_err(&dev->dev, "failed to send control message: %d\n", r);
128 static int ch341_control_in(struct usb_device *dev,
129 u8 request, u16 value, u16 index,
130 char *buf, unsigned bufsize)
134 dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__,
135 request, value, index, bufsize);
137 r = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), request,
138 USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
139 value, index, buf, bufsize, DEFAULT_TIMEOUT);
140 if (r < (int)bufsize) {
143 "short control message received (%d < %u)\n",
148 dev_err(&dev->dev, "failed to receive control message: %d\n",
156 #define CH341_CLKRATE 48000000
157 #define CH341_CLK_DIV(ps, fact) (1 << (12 - 3 * (ps) - (fact)))
158 #define CH341_MIN_RATE(ps) (CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512))
160 static const speed_t ch341_min_rates[] = {
167 /* Supported range is 46 to 3000000 bps. */
168 #define CH341_MIN_BPS DIV_ROUND_UP(CH341_CLKRATE, CH341_CLK_DIV(0, 0) * 256)
169 #define CH341_MAX_BPS (CH341_CLKRATE / (CH341_CLK_DIV(3, 0) * 2))
172 * The device line speed is given by the following equation:
174 * baudrate = 48000000 / (2^(12 - 3 * ps - fact) * div), where
178 * 2 <= div <= 256 if fact = 0, or
179 * 9 <= div <= 256 if fact = 1
181 static int ch341_get_divisor(struct ch341_private *priv, speed_t speed)
183 unsigned int fact, div, clk_div;
184 bool force_fact0 = false;
188 * Clamp to supported range, this makes the (ps < 0) and (div < 2)
189 * sanity checks below redundant.
191 speed = clamp_val(speed, CH341_MIN_BPS, CH341_MAX_BPS);
194 * Start with highest possible base clock (fact = 1) that will give a
195 * divisor strictly less than 512.
198 for (ps = 3; ps >= 0; ps--) {
199 if (speed > ch341_min_rates[ps])
206 /* Determine corresponding divisor, rounding down. */
207 clk_div = CH341_CLK_DIV(ps, fact);
208 div = CH341_CLKRATE / (clk_div * speed);
210 /* Some devices require a lower base clock if ps < 3. */
211 if (ps < 3 && (priv->quirks & CH341_QUIRK_LIMITED_PRESCALER))
214 /* Halve base clock (fact = 0) if required. */
215 if (div < 9 || div > 255 || force_fact0) {
225 * Pick next divisor if resulting rate is closer to the requested one,
226 * scale up to avoid rounding errors on low rates.
228 if (16 * CH341_CLKRATE / (clk_div * div) - 16 * speed >=
229 16 * speed - 16 * CH341_CLKRATE / (clk_div * (div + 1)))
233 * Prefer lower base clock (fact = 0) if even divisor.
235 * Note that this makes the receiver more tolerant to errors.
237 if (fact == 1 && div % 2 == 0) {
242 return (0x100 - div) << 8 | fact << 2 | ps;
245 static int ch341_set_baudrate_lcr(struct usb_device *dev,
246 struct ch341_private *priv,
247 speed_t baud_rate, u8 lcr)
255 val = ch341_get_divisor(priv, baud_rate);
260 * CH341A buffers data until a full endpoint-size packet (32 bytes)
261 * has been received unless bit 7 is set.
263 * At least one device with version 0x27 appears to have this bit
266 if (priv->version > 0x27)
269 r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
270 CH341_REG_DIVISOR << 8 | CH341_REG_PRESCALER,
276 * Chip versions before version 0x30 as read using
277 * CH341_REQ_READ_VERSION used separate registers for line control
278 * (stop bits, parity and word length). Version 0x30 and above use
279 * CH341_REG_LCR only and CH341_REG_LCR2 is always set to zero.
281 if (priv->version < 0x30)
284 r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
285 CH341_REG_LCR2 << 8 | CH341_REG_LCR, lcr);
292 static int ch341_set_handshake(struct usb_device *dev, u8 control)
294 return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0);
297 static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
299 const unsigned int size = 2;
304 buffer = kmalloc(size, GFP_KERNEL);
308 r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size);
312 spin_lock_irqsave(&priv->lock, flags);
313 priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT;
314 spin_unlock_irqrestore(&priv->lock, flags);
320 /* -------------------------------------------------------------------------- */
322 static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
324 const unsigned int size = 2;
328 buffer = kmalloc(size, GFP_KERNEL);
332 /* expect two bytes 0x27 0x00 */
333 r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size);
337 priv->version = buffer[0];
338 dev_dbg(&dev->dev, "Chip version: 0x%02x\n", priv->version);
340 r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
344 r = ch341_set_baudrate_lcr(dev, priv, priv->baud_rate, priv->lcr);
348 r = ch341_set_handshake(dev, priv->mcr);
354 static int ch341_detect_quirks(struct usb_serial_port *port)
356 struct ch341_private *priv = usb_get_serial_port_data(port);
357 struct usb_device *udev = port->serial->dev;
358 const unsigned int size = 2;
359 unsigned long quirks = 0;
363 buffer = kmalloc(size, GFP_KERNEL);
368 * A subset of CH34x devices does not support all features. The
369 * prescaler is limited and there is no support for sending a RS232
370 * break condition. A read failure when trying to set up the latter is
371 * used to detect these devices.
373 r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0), CH341_REQ_READ_REG,
374 USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN,
375 CH341_REG_BREAK, 0, buffer, size, DEFAULT_TIMEOUT);
377 dev_info(&port->dev, "break control not supported, using simulated break\n");
378 quirks = CH341_QUIRK_LIMITED_PRESCALER | CH341_QUIRK_SIMULATE_BREAK;
386 dev_err(&port->dev, "failed to read break control: %d\n", r);
395 dev_dbg(&port->dev, "enabling quirk flags: 0x%02lx\n", quirks);
396 priv->quirks |= quirks;
402 static int ch341_port_probe(struct usb_serial_port *port)
404 struct ch341_private *priv;
407 priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL);
411 spin_lock_init(&priv->lock);
412 priv->baud_rate = DEFAULT_BAUD_RATE;
414 * Some CH340 devices appear unable to change the initial LCR
415 * settings, so set a sane 8N1 default.
417 priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8;
419 r = ch341_configure(port->serial->dev, priv);
423 usb_set_serial_port_data(port, priv);
425 r = ch341_detect_quirks(port);
435 static int ch341_port_remove(struct usb_serial_port *port)
437 struct ch341_private *priv;
439 priv = usb_get_serial_port_data(port);
445 static int ch341_carrier_raised(struct usb_serial_port *port)
447 struct ch341_private *priv = usb_get_serial_port_data(port);
448 if (priv->msr & CH341_BIT_DCD)
453 static void ch341_dtr_rts(struct usb_serial_port *port, int on)
455 struct ch341_private *priv = usb_get_serial_port_data(port);
458 /* drop DTR and RTS */
459 spin_lock_irqsave(&priv->lock, flags);
461 priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR;
463 priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR);
464 spin_unlock_irqrestore(&priv->lock, flags);
465 ch341_set_handshake(port->serial->dev, priv->mcr);
468 static void ch341_close(struct usb_serial_port *port)
470 usb_serial_generic_close(port);
471 usb_kill_urb(port->interrupt_in_urb);
475 /* open this device, set default parameters */
476 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
478 struct ch341_private *priv = usb_get_serial_port_data(port);
482 ch341_set_termios(tty, port, NULL);
484 dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__);
485 r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
487 dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n",
492 r = ch341_get_status(port->serial->dev, priv);
494 dev_err(&port->dev, "failed to read modem status: %d\n", r);
495 goto err_kill_interrupt_urb;
498 r = usb_serial_generic_open(tty, port);
500 goto err_kill_interrupt_urb;
504 err_kill_interrupt_urb:
505 usb_kill_urb(port->interrupt_in_urb);
510 /* Old_termios contains the original termios settings and
511 * tty->termios contains the new setting to be used.
513 static void ch341_set_termios(struct tty_struct *tty,
514 struct usb_serial_port *port, struct ktermios *old_termios)
516 struct ch341_private *priv = usb_get_serial_port_data(port);
522 /* redundant changes may cause the chip to lose bytes */
523 if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios))
526 baud_rate = tty_get_baud_rate(tty);
528 lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX;
530 switch (C_CSIZE(tty)) {
532 lcr |= CH341_LCR_CS5;
535 lcr |= CH341_LCR_CS6;
538 lcr |= CH341_LCR_CS7;
541 lcr |= CH341_LCR_CS8;
546 lcr |= CH341_LCR_ENABLE_PAR;
547 if (C_PARODD(tty) == 0)
548 lcr |= CH341_LCR_PAR_EVEN;
550 lcr |= CH341_LCR_MARK_SPACE;
554 lcr |= CH341_LCR_STOP_BITS_2;
557 priv->baud_rate = baud_rate;
559 r = ch341_set_baudrate_lcr(port->serial->dev, priv,
560 priv->baud_rate, lcr);
561 if (r < 0 && old_termios) {
562 priv->baud_rate = tty_termios_baud_rate(old_termios);
563 tty_termios_copy_hw(&tty->termios, old_termios);
569 spin_lock_irqsave(&priv->lock, flags);
570 if (C_BAUD(tty) == B0)
571 priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS);
572 else if (old_termios && (old_termios->c_cflag & CBAUD) == B0)
573 priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS);
574 spin_unlock_irqrestore(&priv->lock, flags);
576 ch341_set_handshake(port->serial->dev, priv->mcr);
580 * A subset of all CH34x devices don't support a real break condition and
581 * reading CH341_REG_BREAK fails (see also ch341_detect_quirks). This function
582 * simulates a break condition by lowering the baud rate to the minimum
583 * supported by the hardware upon enabling the break condition and sending
586 * Incoming data is corrupted while the break condition is being simulated.
588 * Normally the duration of the break condition can be controlled individually
589 * by userspace using TIOCSBRK and TIOCCBRK or by passing an argument to
590 * TCSBRKP. Due to how the simulation is implemented the duration can't be
591 * controlled. The duration is always about (1s / 46bd * 9bit) = 196ms.
593 static void ch341_simulate_break(struct tty_struct *tty, int break_state)
595 struct usb_serial_port *port = tty->driver_data;
596 struct ch341_private *priv = usb_get_serial_port_data(port);
597 unsigned long now, delay;
600 if (break_state != 0) {
601 dev_dbg(&port->dev, "enter break state requested\n");
603 r = ch341_set_baudrate_lcr(port->serial->dev, priv,
605 CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8);
608 "failed to change baud rate to %u: %d\n",
613 r = tty_put_char(tty, '\0');
616 "failed to write NUL byte for simulated break condition: %d\n",
622 * Compute expected transmission duration including safety
623 * margin. The original baud rate is only restored after the
624 * computed point in time.
626 * 11 bits = 1 start, 8 data, 1 stop, 1 margin
628 priv->break_end = jiffies + (11 * HZ / CH341_MIN_BPS);
633 dev_dbg(&port->dev, "leave break state requested\n");
637 if (time_before(now, priv->break_end)) {
638 /* Wait until NUL byte is written */
639 delay = priv->break_end - now;
641 "wait %d ms while transmitting NUL byte at %u baud\n",
642 jiffies_to_msecs(delay), CH341_MIN_BPS);
643 schedule_timeout_interruptible(delay);
647 /* Restore original baud rate */
648 r = ch341_set_baudrate_lcr(port->serial->dev, priv, priv->baud_rate,
652 "restoring original baud rate of %u failed: %d\n",
656 static void ch341_break_ctl(struct tty_struct *tty, int break_state)
658 const uint16_t ch341_break_reg =
659 ((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK;
660 struct usb_serial_port *port = tty->driver_data;
661 struct ch341_private *priv = usb_get_serial_port_data(port);
663 uint16_t reg_contents;
666 if (priv->quirks & CH341_QUIRK_SIMULATE_BREAK) {
667 ch341_simulate_break(tty, break_state);
671 break_reg = kmalloc(2, GFP_KERNEL);
675 r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG,
676 ch341_break_reg, 0, break_reg, 2);
678 dev_err(&port->dev, "%s - USB control read error (%d)\n",
682 dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n",
683 __func__, break_reg[0], break_reg[1]);
684 if (break_state != 0) {
685 dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__);
686 break_reg[0] &= ~CH341_NBREAK_BITS;
687 break_reg[1] &= ~CH341_LCR_ENABLE_TX;
689 dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__);
690 break_reg[0] |= CH341_NBREAK_BITS;
691 break_reg[1] |= CH341_LCR_ENABLE_TX;
693 dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n",
694 __func__, break_reg[0], break_reg[1]);
695 reg_contents = get_unaligned_le16(break_reg);
696 r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG,
697 ch341_break_reg, reg_contents);
699 dev_err(&port->dev, "%s - USB control write error (%d)\n",
705 static int ch341_tiocmset(struct tty_struct *tty,
706 unsigned int set, unsigned int clear)
708 struct usb_serial_port *port = tty->driver_data;
709 struct ch341_private *priv = usb_get_serial_port_data(port);
713 spin_lock_irqsave(&priv->lock, flags);
715 priv->mcr |= CH341_BIT_RTS;
717 priv->mcr |= CH341_BIT_DTR;
718 if (clear & TIOCM_RTS)
719 priv->mcr &= ~CH341_BIT_RTS;
720 if (clear & TIOCM_DTR)
721 priv->mcr &= ~CH341_BIT_DTR;
723 spin_unlock_irqrestore(&priv->lock, flags);
725 return ch341_set_handshake(port->serial->dev, control);
728 static void ch341_update_status(struct usb_serial_port *port,
729 unsigned char *data, size_t len)
731 struct ch341_private *priv = usb_get_serial_port_data(port);
732 struct tty_struct *tty;
740 status = ~data[2] & CH341_BITS_MODEM_STAT;
742 spin_lock_irqsave(&priv->lock, flags);
743 delta = status ^ priv->msr;
745 spin_unlock_irqrestore(&priv->lock, flags);
747 if (data[1] & CH341_MULT_STAT)
748 dev_dbg(&port->dev, "%s - multiple status change\n", __func__);
753 if (delta & CH341_BIT_CTS)
755 if (delta & CH341_BIT_DSR)
757 if (delta & CH341_BIT_RI)
759 if (delta & CH341_BIT_DCD) {
761 tty = tty_port_tty_get(&port->port);
763 usb_serial_handle_dcd_change(port, tty,
764 status & CH341_BIT_DCD);
769 wake_up_interruptible(&port->port.delta_msr_wait);
772 static void ch341_read_int_callback(struct urb *urb)
774 struct usb_serial_port *port = urb->context;
775 unsigned char *data = urb->transfer_buffer;
776 unsigned int len = urb->actual_length;
779 switch (urb->status) {
786 /* this urb is terminated, clean up */
787 dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n",
788 __func__, urb->status);
791 dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n",
792 __func__, urb->status);
796 usb_serial_debug_data(&port->dev, __func__, len, data);
797 ch341_update_status(port, data, len);
799 status = usb_submit_urb(urb, GFP_ATOMIC);
801 dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n",
806 static int ch341_tiocmget(struct tty_struct *tty)
808 struct usb_serial_port *port = tty->driver_data;
809 struct ch341_private *priv = usb_get_serial_port_data(port);
815 spin_lock_irqsave(&priv->lock, flags);
818 spin_unlock_irqrestore(&priv->lock, flags);
820 result = ((mcr & CH341_BIT_DTR) ? TIOCM_DTR : 0)
821 | ((mcr & CH341_BIT_RTS) ? TIOCM_RTS : 0)
822 | ((status & CH341_BIT_CTS) ? TIOCM_CTS : 0)
823 | ((status & CH341_BIT_DSR) ? TIOCM_DSR : 0)
824 | ((status & CH341_BIT_RI) ? TIOCM_RI : 0)
825 | ((status & CH341_BIT_DCD) ? TIOCM_CD : 0);
827 dev_dbg(&port->dev, "%s - result = %x\n", __func__, result);
832 static int ch341_reset_resume(struct usb_serial *serial)
834 struct usb_serial_port *port = serial->port[0];
835 struct ch341_private *priv;
838 priv = usb_get_serial_port_data(port);
842 /* reconfigure ch341 serial port after bus-reset */
843 ch341_configure(serial->dev, priv);
845 if (tty_port_initialized(&port->port)) {
846 ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
848 dev_err(&port->dev, "failed to submit interrupt urb: %d\n",
853 ret = ch341_get_status(port->serial->dev, priv);
855 dev_err(&port->dev, "failed to read modem status: %d\n",
860 return usb_serial_generic_resume(serial);
863 static struct usb_serial_driver ch341_device = {
865 .owner = THIS_MODULE,
866 .name = "ch341-uart",
868 .id_table = id_table,
871 .dtr_rts = ch341_dtr_rts,
872 .carrier_raised = ch341_carrier_raised,
873 .close = ch341_close,
874 .set_termios = ch341_set_termios,
875 .break_ctl = ch341_break_ctl,
876 .tiocmget = ch341_tiocmget,
877 .tiocmset = ch341_tiocmset,
878 .tiocmiwait = usb_serial_generic_tiocmiwait,
879 .read_int_callback = ch341_read_int_callback,
880 .port_probe = ch341_port_probe,
881 .port_remove = ch341_port_remove,
882 .reset_resume = ch341_reset_resume,
885 static struct usb_serial_driver * const serial_drivers[] = {
889 module_usb_serial_driver(serial_drivers, id_table);
891 MODULE_LICENSE("GPL v2");