// SPDX-License-Identifier: GPL-2.0 /* * Copyright 2007, Frank A Kingswood * Copyright 2007, Werner Cornelius * Copyright 2009, Boris Hajduk * * ch341.c implements a serial port driver for the Winchiphead CH341. * * The CH341 device can be used to implement an RS232 asynchronous * serial port, an IEEE-1284 parallel printer port or a memory-like * interface. In all cases the CH341 supports an I2C interface as well. * This driver only supports the asynchronous serial interface. */ #include #include #include #include #include #include #include #include #define DEFAULT_BAUD_RATE 9600 #define DEFAULT_TIMEOUT 1000 /* flags for IO-Bits */ #define CH341_BIT_RTS (1 << 6) #define CH341_BIT_DTR (1 << 5) /******************************/ /* interrupt pipe definitions */ /******************************/ /* always 4 interrupt bytes */ /* first irq byte normally 0x08 */ /* second irq byte base 0x7d + below */ /* third irq byte base 0x94 + below */ /* fourth irq byte normally 0xee */ /* second interrupt byte */ #define CH341_MULT_STAT 0x04 /* multiple status since last interrupt event */ /* status returned in third interrupt answer byte, inverted in data from irq */ #define CH341_BIT_CTS 0x01 #define CH341_BIT_DSR 0x02 #define CH341_BIT_RI 0x04 #define CH341_BIT_DCD 0x08 #define CH341_BITS_MODEM_STAT 0x0f /* all bits */ /* Break support - the information used to implement this was gleaned from * the Net/FreeBSD uchcom.c driver by Takanori Watanabe. Domo arigato. */ #define CH341_REQ_READ_VERSION 0x5F #define CH341_REQ_WRITE_REG 0x9A #define CH341_REQ_READ_REG 0x95 #define CH341_REQ_SERIAL_INIT 0xA1 #define CH341_REQ_MODEM_CTRL 0xA4 #define CH341_REG_BREAK 0x05 #define CH341_REG_PRESCALER 0x12 #define CH341_REG_DIVISOR 0x13 #define CH341_REG_LCR 0x18 #define CH341_REG_LCR2 0x25 #define CH341_NBREAK_BITS 0x01 #define CH341_LCR_ENABLE_RX 0x80 #define CH341_LCR_ENABLE_TX 0x40 #define CH341_LCR_MARK_SPACE 0x20 #define CH341_LCR_PAR_EVEN 0x10 #define CH341_LCR_ENABLE_PAR 0x08 #define CH341_LCR_STOP_BITS_2 0x04 #define CH341_LCR_CS8 0x03 #define CH341_LCR_CS7 0x02 #define CH341_LCR_CS6 0x01 #define CH341_LCR_CS5 0x00 #define CH341_QUIRK_LIMITED_PRESCALER BIT(0) #define CH341_QUIRK_SIMULATE_BREAK BIT(1) static const struct usb_device_id id_table[] = { { USB_DEVICE(0x1a86, 0x5523) }, { USB_DEVICE(0x1a86, 0x7522) }, { USB_DEVICE(0x1a86, 0x7523) }, { USB_DEVICE(0x2184, 0x0057) }, { USB_DEVICE(0x4348, 0x5523) }, { USB_DEVICE(0x9986, 0x7523) }, { }, }; MODULE_DEVICE_TABLE(usb, id_table); struct ch341_private { spinlock_t lock; /* access lock */ unsigned baud_rate; /* set baud rate */ u8 mcr; u8 msr; u8 lcr; unsigned long quirks; u8 version; unsigned long break_end; }; static void ch341_set_termios(struct tty_struct *tty, struct usb_serial_port *port, const struct ktermios *old_termios); static int ch341_control_out(struct usb_device *dev, u8 request, u16 value, u16 index) { int r; dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x)\n", __func__, request, value, index); r = usb_control_msg(dev, usb_sndctrlpipe(dev, 0), request, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT, value, index, NULL, 0, DEFAULT_TIMEOUT); if (r < 0) dev_err(&dev->dev, "failed to send control message: %d\n", r); return r; } static int ch341_control_in(struct usb_device *dev, u8 request, u16 value, u16 index, char *buf, unsigned bufsize) { int r; dev_dbg(&dev->dev, "%s - (%02x,%04x,%04x,%u)\n", __func__, request, value, index, bufsize); r = usb_control_msg_recv(dev, 0, request, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN, value, index, buf, bufsize, DEFAULT_TIMEOUT, GFP_KERNEL); if (r) { dev_err(&dev->dev, "failed to receive control message: %d\n", r); return r; } return 0; } #define CH341_CLKRATE 48000000 #define CH341_CLK_DIV(ps, fact) (1 << (12 - 3 * (ps) - (fact))) #define CH341_MIN_RATE(ps) (CH341_CLKRATE / (CH341_CLK_DIV((ps), 1) * 512)) static const speed_t ch341_min_rates[] = { CH341_MIN_RATE(0), CH341_MIN_RATE(1), CH341_MIN_RATE(2), CH341_MIN_RATE(3), }; /* Supported range is 46 to 3000000 bps. */ #define CH341_MIN_BPS DIV_ROUND_UP(CH341_CLKRATE, CH341_CLK_DIV(0, 0) * 256) #define CH341_MAX_BPS (CH341_CLKRATE / (CH341_CLK_DIV(3, 0) * 2)) /* * The device line speed is given by the following equation: * * baudrate = 48000000 / (2^(12 - 3 * ps - fact) * div), where * * 0 <= ps <= 3, * 0 <= fact <= 1, * 2 <= div <= 256 if fact = 0, or * 9 <= div <= 256 if fact = 1 */ static int ch341_get_divisor(struct ch341_private *priv, speed_t speed) { unsigned int fact, div, clk_div; bool force_fact0 = false; int ps; /* * Clamp to supported range, this makes the (ps < 0) and (div < 2) * sanity checks below redundant. */ speed = clamp_val(speed, CH341_MIN_BPS, CH341_MAX_BPS); /* * Start with highest possible base clock (fact = 1) that will give a * divisor strictly less than 512. */ fact = 1; for (ps = 3; ps >= 0; ps--) { if (speed > ch341_min_rates[ps]) break; } if (ps < 0) return -EINVAL; /* Determine corresponding divisor, rounding down. */ clk_div = CH341_CLK_DIV(ps, fact); div = CH341_CLKRATE / (clk_div * speed); /* Some devices require a lower base clock if ps < 3. */ if (ps < 3 && (priv->quirks & CH341_QUIRK_LIMITED_PRESCALER)) force_fact0 = true; /* Halve base clock (fact = 0) if required. */ if (div < 9 || div > 255 || force_fact0) { div /= 2; clk_div *= 2; fact = 0; } if (div < 2) return -EINVAL; /* * Pick next divisor if resulting rate is closer to the requested one, * scale up to avoid rounding errors on low rates. */ if (16 * CH341_CLKRATE / (clk_div * div) - 16 * speed >= 16 * speed - 16 * CH341_CLKRATE / (clk_div * (div + 1))) div++; /* * Prefer lower base clock (fact = 0) if even divisor. * * Note that this makes the receiver more tolerant to errors. */ if (fact == 1 && div % 2 == 0) { div /= 2; fact = 0; } return (0x100 - div) << 8 | fact << 2 | ps; } static int ch341_set_baudrate_lcr(struct usb_device *dev, struct ch341_private *priv, speed_t baud_rate, u8 lcr) { int val; int r; if (!baud_rate) return -EINVAL; val = ch341_get_divisor(priv, baud_rate); if (val < 0) return -EINVAL; /* * CH341A buffers data until a full endpoint-size packet (32 bytes) * has been received unless bit 7 is set. * * At least one device with version 0x27 appears to have this bit * inverted. */ if (priv->version > 0x27) val |= BIT(7); r = ch341_control_out(dev, CH341_REQ_WRITE_REG, CH341_REG_DIVISOR << 8 | CH341_REG_PRESCALER, val); if (r) return r; /* * Chip versions before version 0x30 as read using * CH341_REQ_READ_VERSION used separate registers for line control * (stop bits, parity and word length). Version 0x30 and above use * CH341_REG_LCR only and CH341_REG_LCR2 is always set to zero. */ if (priv->version < 0x30) return 0; r = ch341_control_out(dev, CH341_REQ_WRITE_REG, CH341_REG_LCR2 << 8 | CH341_REG_LCR, lcr); if (r) return r; return r; } static int ch341_set_handshake(struct usb_device *dev, u8 control) { return ch341_control_out(dev, CH341_REQ_MODEM_CTRL, ~control, 0); } static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv) { const unsigned int size = 2; u8 buffer[2]; int r; unsigned long flags; r = ch341_control_in(dev, CH341_REQ_READ_REG, 0x0706, 0, buffer, size); if (r) return r; spin_lock_irqsave(&priv->lock, flags); priv->msr = (~(*buffer)) & CH341_BITS_MODEM_STAT; spin_unlock_irqrestore(&priv->lock, flags); return 0; } /* -------------------------------------------------------------------------- */ static int ch341_configure(struct usb_device *dev, struct ch341_private *priv) { const unsigned int size = 2; u8 buffer[2]; int r; /* expect two bytes 0x27 0x00 */ r = ch341_control_in(dev, CH341_REQ_READ_VERSION, 0, 0, buffer, size); if (r) return r; priv->version = buffer[0]; dev_dbg(&dev->dev, "Chip version: 0x%02x\n", priv->version); r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0); if (r < 0) return r; r = ch341_set_baudrate_lcr(dev, priv, priv->baud_rate, priv->lcr); if (r < 0) return r; r = ch341_set_handshake(dev, priv->mcr); if (r < 0) return r; return 0; } static int ch341_detect_quirks(struct usb_serial_port *port) { struct ch341_private *priv = usb_get_serial_port_data(port); struct usb_device *udev = port->serial->dev; const unsigned int size = 2; unsigned long quirks = 0; u8 buffer[2]; int r; /* * A subset of CH34x devices does not support all features. The * prescaler is limited and there is no support for sending a RS232 * break condition. A read failure when trying to set up the latter is * used to detect these devices. */ r = usb_control_msg_recv(udev, 0, CH341_REQ_READ_REG, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN, CH341_REG_BREAK, 0, &buffer, size, DEFAULT_TIMEOUT, GFP_KERNEL); if (r == -EPIPE) { dev_info(&port->dev, "break control not supported, using simulated break\n"); quirks = CH341_QUIRK_LIMITED_PRESCALER | CH341_QUIRK_SIMULATE_BREAK; r = 0; } else if (r) { dev_err(&port->dev, "failed to read break control: %d\n", r); } if (quirks) { dev_dbg(&port->dev, "enabling quirk flags: 0x%02lx\n", quirks); priv->quirks |= quirks; } return r; } static int ch341_port_probe(struct usb_serial_port *port) { struct ch341_private *priv; int r; priv = kzalloc(sizeof(struct ch341_private), GFP_KERNEL); if (!priv) return -ENOMEM; spin_lock_init(&priv->lock); priv->baud_rate = DEFAULT_BAUD_RATE; /* * Some CH340 devices appear unable to change the initial LCR * settings, so set a sane 8N1 default. */ priv->lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8; r = ch341_configure(port->serial->dev, priv); if (r < 0) goto error; usb_set_serial_port_data(port, priv); r = ch341_detect_quirks(port); if (r < 0) goto error; return 0; error: kfree(priv); return r; } static void ch341_port_remove(struct usb_serial_port *port) { struct ch341_private *priv; priv = usb_get_serial_port_data(port); kfree(priv); } static int ch341_carrier_raised(struct usb_serial_port *port) { struct ch341_private *priv = usb_get_serial_port_data(port); if (priv->msr & CH341_BIT_DCD) return 1; return 0; } static void ch341_dtr_rts(struct usb_serial_port *port, int on) { struct ch341_private *priv = usb_get_serial_port_data(port); unsigned long flags; /* drop DTR and RTS */ spin_lock_irqsave(&priv->lock, flags); if (on) priv->mcr |= CH341_BIT_RTS | CH341_BIT_DTR; else priv->mcr &= ~(CH341_BIT_RTS | CH341_BIT_DTR); spin_unlock_irqrestore(&priv->lock, flags); ch341_set_handshake(port->serial->dev, priv->mcr); } static void ch341_close(struct usb_serial_port *port) { usb_serial_generic_close(port); usb_kill_urb(port->interrupt_in_urb); } /* open this device, set default parameters */ static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port) { struct ch341_private *priv = usb_get_serial_port_data(port); int r; if (tty) ch341_set_termios(tty, port, NULL); dev_dbg(&port->dev, "%s - submitting interrupt urb\n", __func__); r = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL); if (r) { dev_err(&port->dev, "%s - failed to submit interrupt urb: %d\n", __func__, r); return r; } r = ch341_get_status(port->serial->dev, priv); if (r < 0) { dev_err(&port->dev, "failed to read modem status: %d\n", r); goto err_kill_interrupt_urb; } r = usb_serial_generic_open(tty, port); if (r) goto err_kill_interrupt_urb; return 0; err_kill_interrupt_urb: usb_kill_urb(port->interrupt_in_urb); return r; } /* Old_termios contains the original termios settings and * tty->termios contains the new setting to be used. */ static void ch341_set_termios(struct tty_struct *tty, struct usb_serial_port *port, const struct ktermios *old_termios) { struct ch341_private *priv = usb_get_serial_port_data(port); unsigned baud_rate; unsigned long flags; u8 lcr; int r; /* redundant changes may cause the chip to lose bytes */ if (old_termios && !tty_termios_hw_change(&tty->termios, old_termios)) return; baud_rate = tty_get_baud_rate(tty); lcr = CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX; switch (C_CSIZE(tty)) { case CS5: lcr |= CH341_LCR_CS5; break; case CS6: lcr |= CH341_LCR_CS6; break; case CS7: lcr |= CH341_LCR_CS7; break; case CS8: lcr |= CH341_LCR_CS8; break; } if (C_PARENB(tty)) { lcr |= CH341_LCR_ENABLE_PAR; if (C_PARODD(tty) == 0) lcr |= CH341_LCR_PAR_EVEN; if (C_CMSPAR(tty)) lcr |= CH341_LCR_MARK_SPACE; } if (C_CSTOPB(tty)) lcr |= CH341_LCR_STOP_BITS_2; if (baud_rate) { priv->baud_rate = baud_rate; r = ch341_set_baudrate_lcr(port->serial->dev, priv, priv->baud_rate, lcr); if (r < 0 && old_termios) { priv->baud_rate = tty_termios_baud_rate(old_termios); tty_termios_copy_hw(&tty->termios, old_termios); } else if (r == 0) { priv->lcr = lcr; } } spin_lock_irqsave(&priv->lock, flags); if (C_BAUD(tty) == B0) priv->mcr &= ~(CH341_BIT_DTR | CH341_BIT_RTS); else if (old_termios && (old_termios->c_cflag & CBAUD) == B0) priv->mcr |= (CH341_BIT_DTR | CH341_BIT_RTS); spin_unlock_irqrestore(&priv->lock, flags); ch341_set_handshake(port->serial->dev, priv->mcr); } /* * A subset of all CH34x devices don't support a real break condition and * reading CH341_REG_BREAK fails (see also ch341_detect_quirks). This function * simulates a break condition by lowering the baud rate to the minimum * supported by the hardware upon enabling the break condition and sending * a NUL byte. * * Incoming data is corrupted while the break condition is being simulated. * * Normally the duration of the break condition can be controlled individually * by userspace using TIOCSBRK and TIOCCBRK or by passing an argument to * TCSBRKP. Due to how the simulation is implemented the duration can't be * controlled. The duration is always about (1s / 46bd * 9bit) = 196ms. */ static int ch341_simulate_break(struct tty_struct *tty, int break_state) { struct usb_serial_port *port = tty->driver_data; struct ch341_private *priv = usb_get_serial_port_data(port); unsigned long now, delay; int r, r2; if (break_state != 0) { dev_dbg(&port->dev, "enter break state requested\n"); r = ch341_set_baudrate_lcr(port->serial->dev, priv, CH341_MIN_BPS, CH341_LCR_ENABLE_RX | CH341_LCR_ENABLE_TX | CH341_LCR_CS8); if (r < 0) { dev_err(&port->dev, "failed to change baud rate to %u: %d\n", CH341_MIN_BPS, r); goto restore; } r = tty_put_char(tty, '\0'); if (r < 0) { dev_err(&port->dev, "failed to write NUL byte for simulated break condition: %d\n", r); goto restore; } /* * Compute expected transmission duration including safety * margin. The original baud rate is only restored after the * computed point in time. * * 11 bits = 1 start, 8 data, 1 stop, 1 margin */ priv->break_end = jiffies + (11 * HZ / CH341_MIN_BPS); return 0; } dev_dbg(&port->dev, "leave break state requested\n"); now = jiffies; if (time_before(now, priv->break_end)) { /* Wait until NUL byte is written */ delay = priv->break_end - now; dev_dbg(&port->dev, "wait %d ms while transmitting NUL byte at %u baud\n", jiffies_to_msecs(delay), CH341_MIN_BPS); schedule_timeout_interruptible(delay); } r = 0; restore: /* Restore original baud rate */ r2 = ch341_set_baudrate_lcr(port->serial->dev, priv, priv->baud_rate, priv->lcr); if (r2 < 0) { dev_err(&port->dev, "restoring original baud rate of %u failed: %d\n", priv->baud_rate, r2); return r2; } return r; } static int ch341_break_ctl(struct tty_struct *tty, int break_state) { const uint16_t ch341_break_reg = ((uint16_t) CH341_REG_LCR << 8) | CH341_REG_BREAK; struct usb_serial_port *port = tty->driver_data; struct ch341_private *priv = usb_get_serial_port_data(port); int r; uint16_t reg_contents; uint8_t break_reg[2]; if (priv->quirks & CH341_QUIRK_SIMULATE_BREAK) return ch341_simulate_break(tty, break_state); r = ch341_control_in(port->serial->dev, CH341_REQ_READ_REG, ch341_break_reg, 0, break_reg, 2); if (r) { dev_err(&port->dev, "%s - USB control read error (%d)\n", __func__, r); if (r > 0) r = -EIO; return r; } dev_dbg(&port->dev, "%s - initial ch341 break register contents - reg1: %x, reg2: %x\n", __func__, break_reg[0], break_reg[1]); if (break_state != 0) { dev_dbg(&port->dev, "%s - Enter break state requested\n", __func__); break_reg[0] &= ~CH341_NBREAK_BITS; break_reg[1] &= ~CH341_LCR_ENABLE_TX; } else { dev_dbg(&port->dev, "%s - Leave break state requested\n", __func__); break_reg[0] |= CH341_NBREAK_BITS; break_reg[1] |= CH341_LCR_ENABLE_TX; } dev_dbg(&port->dev, "%s - New ch341 break register contents - reg1: %x, reg2: %x\n", __func__, break_reg[0], break_reg[1]); reg_contents = get_unaligned_le16(break_reg); r = ch341_control_out(port->serial->dev, CH341_REQ_WRITE_REG, ch341_break_reg, reg_contents); if (r < 0) { dev_err(&port->dev, "%s - USB control write error (%d)\n", __func__, r); return r; } return 0; } static int ch341_tiocmset(struct tty_struct *tty, unsigned int set, unsigned int clear) { struct usb_serial_port *port = tty->driver_data; struct ch341_private *priv = usb_get_serial_port_data(port); unsigned long flags; u8 control; spin_lock_irqsave(&priv->lock, flags); if (set & TIOCM_RTS) priv->mcr |= CH341_BIT_RTS; if (set & TIOCM_DTR) priv->mcr |= CH341_BIT_DTR; if (clear & TIOCM_RTS) priv->mcr &= ~CH341_BIT_RTS; if (clear & TIOCM_DTR) priv->mcr &= ~CH341_BIT_DTR; control = priv->mcr; spin_unlock_irqrestore(&priv->lock, flags); return ch341_set_handshake(port->serial->dev, control); } static void ch341_update_status(struct usb_serial_port *port, unsigned char *data, size_t len) { struct ch341_private *priv = usb_get_serial_port_data(port); struct tty_struct *tty; unsigned long flags; u8 status; u8 delta; if (len < 4) return; status = ~data[2] & CH341_BITS_MODEM_STAT; spin_lock_irqsave(&priv->lock, flags); delta = status ^ priv->msr; priv->msr = status; spin_unlock_irqrestore(&priv->lock, flags); if (data[1] & CH341_MULT_STAT) dev_dbg(&port->dev, "%s - multiple status change\n", __func__); if (!delta) return; if (delta & CH341_BIT_CTS) port->icount.cts++; if (delta & CH341_BIT_DSR) port->icount.dsr++; if (delta & CH341_BIT_RI) port->icount.rng++; if (delta & CH341_BIT_DCD) { port->icount.dcd++; tty = tty_port_tty_get(&port->port); if (tty) { usb_serial_handle_dcd_change(port, tty, status & CH341_BIT_DCD); tty_kref_put(tty); } } wake_up_interruptible(&port->port.delta_msr_wait); } static void ch341_read_int_callback(struct urb *urb) { struct usb_serial_port *port = urb->context; unsigned char *data = urb->transfer_buffer; unsigned int len = urb->actual_length; int status; switch (urb->status) { case 0: /* success */ break; case -ECONNRESET: case -ENOENT: case -ESHUTDOWN: /* this urb is terminated, clean up */ dev_dbg(&urb->dev->dev, "%s - urb shutting down: %d\n", __func__, urb->status); return; default: dev_dbg(&urb->dev->dev, "%s - nonzero urb status: %d\n", __func__, urb->status); goto exit; } usb_serial_debug_data(&port->dev, __func__, len, data); ch341_update_status(port, data, len); exit: status = usb_submit_urb(urb, GFP_ATOMIC); if (status) { dev_err(&urb->dev->dev, "%s - usb_submit_urb failed: %d\n", __func__, status); } } static int ch341_tiocmget(struct tty_struct *tty) { struct usb_serial_port *port = tty->driver_data; struct ch341_private *priv = usb_get_serial_port_data(port); unsigned long flags; u8 mcr; u8 status; unsigned int result; spin_lock_irqsave(&priv->lock, flags); mcr = priv->mcr; status = priv->msr; spin_unlock_irqrestore(&priv->lock, flags); result = ((mcr & CH341_BIT_DTR) ? TIOCM_DTR : 0) | ((mcr & CH341_BIT_RTS) ? TIOCM_RTS : 0) | ((status & CH341_BIT_CTS) ? TIOCM_CTS : 0) | ((status & CH341_BIT_DSR) ? TIOCM_DSR : 0) | ((status & CH341_BIT_RI) ? TIOCM_RI : 0) | ((status & CH341_BIT_DCD) ? TIOCM_CD : 0); dev_dbg(&port->dev, "%s - result = %x\n", __func__, result); return result; } static int ch341_reset_resume(struct usb_serial *serial) { struct usb_serial_port *port = serial->port[0]; struct ch341_private *priv; int ret; priv = usb_get_serial_port_data(port); if (!priv) return 0; /* reconfigure ch341 serial port after bus-reset */ ch341_configure(serial->dev, priv); if (tty_port_initialized(&port->port)) { ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO); if (ret) { dev_err(&port->dev, "failed to submit interrupt urb: %d\n", ret); return ret; } ret = ch341_get_status(port->serial->dev, priv); if (ret < 0) { dev_err(&port->dev, "failed to read modem status: %d\n", ret); } } return usb_serial_generic_resume(serial); } static struct usb_serial_driver ch341_device = { .driver = { .name = "ch341-uart", }, .id_table = id_table, .num_ports = 1, .open = ch341_open, .dtr_rts = ch341_dtr_rts, .carrier_raised = ch341_carrier_raised, .close = ch341_close, .set_termios = ch341_set_termios, .break_ctl = ch341_break_ctl, .tiocmget = ch341_tiocmget, .tiocmset = ch341_tiocmset, .tiocmiwait = usb_serial_generic_tiocmiwait, .read_int_callback = ch341_read_int_callback, .port_probe = ch341_port_probe, .port_remove = ch341_port_remove, .reset_resume = ch341_reset_resume, }; static struct usb_serial_driver * const serial_drivers[] = { &ch341_device, NULL }; module_usb_serial_driver(serial_drivers, id_table); MODULE_DESCRIPTION("Winchiphead CH341 USB Serial driver"); MODULE_LICENSE("GPL v2");