* Re: [PATCH] usb: serial: ch341: add debugfs interface and clean up
[not found] <CACnaG5x_EPK+PGqdrRO-OgOQ3go8EKFdV+R14bKuc9mTS5r31w@mail.gmail.com>
@ 2026-08-05 15:28 ` Vegom Doster
2026-08-06 4:40 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Vegom Doster @ 2026-08-05 15:28 UTC (permalink / raw)
To: linux-usb
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On Wed, Aug 5, 2026 at 8:27 PM Vegom Doster <vegomdoster@gmail.com> wrote:
> This patch adds a debugfs interface for the CH341 driver, allowing runtime
> inspection of chip version, quirks, and line status. It also adds a 'baud'
> file to test the divisor calculation without hardware.
>
> The patch also cleans up magic numbers, removes duplicate code, and fixes
> several issues:
> - Replace obsolete usb_control_msg() with usb_control_msg_send/recv
> - Convert version>0x27 hack to proper CH341_QUIRK_INVERTED_BIT7
> - Fix baud_rate update in ch341_set_termios (only on success)
> - Use READ_ONCE/WRITE_ONCE for break_end
> - Fix error handling in ch341_reset_resume
> - Add debugfs interface for diagnostics
>
> No functional changes are made to the driver's operation.
>
> Tested on Arch Linux with Arduino Uno (CH340C, 1a86:7523):
> - checkpatch: 0 errors, 0 warnings, 0 checks
> - DTR/RTS (tiocmget/set): PASS
> - Echo at 9600 and 115200 baud: PASS (byte-per-byte)
> - Divisor formula for 15 speeds (300..3000000): PASS (error ≤0.16%)
> - debugfs: tested with custom test script
>
> Signed-off-by: nerolocker <vegomdoster@gmail.com>
>
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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
* Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
* Copyright 2009, Boris Hajduk <boris@hajduk.org>
* Copyright 2026, nerolocker <vegomdoster@gmail.com>
*
* 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 <linux/kernel.h>
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/debugfs.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
#include <linux/unaligned.h>
#define DEFAULT_BAUD_RATE 9600
#define DEFAULT_TIMEOUT 1000
/* flags for IO-Bits */
#define CH341_BIT_RTS BIT(6)
#define CH341_BIT_DTR BIT(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_REG_FLOW_CTL 0x27
#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_FLOW_CTL_NONE 0x00
#define CH341_FLOW_CTL_RTSCTS 0x01
#define CH341_QUIRK_LIMITED_PRESCALER BIT(0)
#define CH341_QUIRK_SIMULATE_BREAK BIT(1)
#define CH341_QUIRK_INVERTED_BIT7 BIT(2)
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 int baud_rate; /* set baud rate */
u8 mcr;
u8 msr;
u8 lcr;
unsigned long quirks;
u8 version;
unsigned long break_end;
struct dentry *debugfs;
unsigned int dbg_speed;
int dbg_divisor;
unsigned int dbg_actual;
};
static void ch341_set_termios(struct tty_struct *tty,
struct usb_serial_port *port,
const struct ktermios *old_termios);
static void ch341_debugfs_init_port(struct usb_serial_port *port,
struct ch341_private *priv);
static void ch341_debugfs_remove_port(struct ch341_private *priv);
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_send(dev, 0, request,
USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
value, index, NULL, 0, DEFAULT_TIMEOUT,
GFP_KERNEL);
if (r)
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 int 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 unsigned int 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, unsigned int 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,
unsigned int 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->quirks & CH341_QUIRK_INVERTED_BIT7))
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);
/*
* 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, so it must not be
* set on those devices.
*/
if (priv->version <= 0x27)
priv->quirks |= CH341_QUIRK_INVERTED_BIT7;
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_obj(struct ch341_private);
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;
ch341_debugfs_init_port(port, priv);
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);
ch341_debugfs_remove_port(priv);
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;
}
static void ch341_set_flow_control(struct tty_struct *tty,
struct usb_serial_port *port,
const struct ktermios *old_termios)
{
u16 flow_ctl;
int r;
if (C_CRTSCTS(tty))
flow_ctl = CH341_FLOW_CTL_RTSCTS;
else
flow_ctl = CH341_FLOW_CTL_NONE;
r = ch341_control_out(port->serial->dev,
CH341_REQ_WRITE_REG,
(CH341_REG_FLOW_CTL << 8) | CH341_REG_FLOW_CTL,
(flow_ctl << 8) | flow_ctl);
if (r < 0 && old_termios) {
tty->termios.c_cflag &= ~CRTSCTS;
tty->termios.c_cflag |= (old_termios->c_cflag & CRTSCTS);
}
}
/* 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 int 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) {
r = ch341_set_baudrate_lcr(port->serial->dev, priv,
baud_rate, lcr);
if (r < 0 && old_termios) {
tty_termios_copy_hw(&tty->termios, old_termios);
} else if (r == 0) {
priv->baud_rate = baud_rate;
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);
ch341_set_flow_control(tty, port, old_termios);
}
/*
* 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
*/
WRITE_ONCE(priv->break_end,
jiffies + (11 * HZ / CH341_MIN_BPS));
return 0;
}
dev_dbg(&port->dev, "leave break state requested\n");
now = jiffies;
delay = READ_ONCE(priv->break_end);
if (time_before(now, delay)) {
/* Wait until NUL byte is written */
delay -= 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 u16 ch341_break_reg = (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);
u16 reg_contents;
u8 break_reg[2];
int r;
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 */
ret = ch341_configure(serial->dev, priv);
if (ret) {
dev_err(&port->dev, "failed to reconfigure after bus reset: %d\n",
ret);
return ret;
}
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);
}
/* -------------------------------------------------------------------------- */
/* debugfs interface */
/* -------------------------------------------------------------------------- */
static struct dentry *ch341_debugfs_root;
/*
* Decode the raw value returned by ch341_get_divisor() back into the actual
* line speed, using the inverse of the formula in that function.
*/
static unsigned int ch341_decode_rate(int val)
{
unsigned int ps = val & 0x03;
unsigned int fact = (val >> 2) & 1;
unsigned int div = 0x100 - (val >> 8);
unsigned int clk_div = 1 << (12 - 3 * ps - fact);
return CH341_CLKRATE / (clk_div * div);
}
static int ch341_debugfs_info_show(struct seq_file *m, void *v)
{
struct ch341_private *priv = m->private;
unsigned long flags;
u8 mcr, msr;
spin_lock_irqsave(&priv->lock, flags);
mcr = priv->mcr;
msr = priv->msr;
spin_unlock_irqrestore(&priv->lock, flags);
seq_printf(m, "version: 0x%02x\n", priv->version);
seq_printf(m, "quirks: 0x%04lx\n", priv->quirks);
seq_printf(m, "baud: %u\n", priv->baud_rate);
seq_printf(m, "mcr: 0x%02x\n", mcr);
seq_printf(m, "msr: 0x%02x\n", msr);
return 0;
}
static int ch341_debugfs_info_open(struct inode *inode, struct file *file)
{
return single_open(file, ch341_debugfs_info_show, inode->i_private);
}
static const struct file_operations ch341_debugfs_info_fops = {
.open = ch341_debugfs_info_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static int ch341_debugfs_baud_show(struct seq_file *m, void *v)
{
struct ch341_private *priv = m->private;
seq_printf(m, "requested: %u\n", priv->dbg_speed);
seq_printf(m, "divisor: 0x%04x\n", priv->dbg_divisor);
seq_printf(m, "actual: %u\n", priv->dbg_actual);
return 0;
}
static int ch341_debugfs_baud_open(struct inode *inode, struct file *file)
{
return single_open(file, ch341_debugfs_baud_show, inode->i_private);
}
/*
* Writing a line speed to this file runs the divisor calculation and reports
* the resulting raw divisor value and the achieved rate. This allows the
* formula in ch341_get_divisor() to be verified from userspace without any
* hardware.
*/
static ssize_t ch341_debugfs_baud_write(struct file *file,
const char __user *buf, size_t count,
loff_t *ppos)
{
struct seq_file *seq = file->private_data;
struct ch341_private *priv = seq->private;
char kbuf[16];
unsigned long speed;
int divisor;
int ret;
if (count >= sizeof(kbuf))
return -EINVAL;
ret = simple_write_to_buffer(kbuf, sizeof(kbuf) - 1, ppos, buf, count);
if (ret < 0)
return ret;
kbuf[ret] = '\0';
ret = kstrtoul(kbuf, 10, &speed);
if (ret)
return ret;
divisor = ch341_get_divisor(priv, speed);
if (divisor < 0)
return -EINVAL;
priv->dbg_speed = speed;
priv->dbg_divisor = divisor;
priv->dbg_actual = ch341_decode_rate(divisor);
return count;
}
static const struct file_operations ch341_debugfs_baud_fops = {
.open = ch341_debugfs_baud_open,
.read = seq_read,
.write = ch341_debugfs_baud_write,
.llseek = seq_lseek,
.release = single_release,
};
static void ch341_debugfs_init_port(struct usb_serial_port *port,
struct ch341_private *priv)
{
priv->debugfs = debugfs_create_dir(dev_name(&port->dev),
ch341_debugfs_root);
debugfs_create_file("info", 0444, priv->debugfs, priv,
&ch341_debugfs_info_fops);
debugfs_create_file("baud", 0644, priv->debugfs, priv,
&ch341_debugfs_baud_fops);
}
static void ch341_debugfs_remove_port(struct ch341_private *priv)
{
debugfs_remove_recursive(priv->debugfs);
priv->debugfs = NULL;
}
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
};
static int __init ch341_init(void)
{
int r;
ch341_debugfs_root = debugfs_create_dir("ch341-uart", NULL);
r = usb_serial_register_drivers(serial_drivers, KBUILD_MODNAME,
id_table);
if (r)
debugfs_remove_recursive(ch341_debugfs_root);
return r;
}
static void __exit ch341_exit(void)
{
usb_serial_deregister_drivers(serial_drivers);
debugfs_remove_recursive(ch341_debugfs_root);
}
module_init(ch341_init);
module_exit(ch341_exit);
MODULE_DESCRIPTION("Winchiphead CH341 USB Serial driver");
MODULE_LICENSE("GPL v2");
[-- Attachment #3: ch341-debugfs.patch --]
[-- Type: text/x-patch, Size: 13803 bytes --]
--- ch341_orig.c 2026-08-05 20:21:58.742065698 +0500
+++ ch341.c 2026-08-05 20:16:58.012117521 +0500
@@ -3,6 +3,7 @@
* Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
* Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
* Copyright 2009, Boris Hajduk <boris@hajduk.org>
+ * Copyright 2026, nerolocker <vegomdoster@gmail.com>
*
* ch341.c implements a serial port driver for the Winchiphead CH341.
*
@@ -16,6 +17,7 @@
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/slab.h>
+#include <linux/debugfs.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
@@ -25,8 +27,8 @@
#define DEFAULT_TIMEOUT 1000
/* flags for IO-Bits */
-#define CH341_BIT_RTS (1 << 6)
-#define CH341_BIT_DTR (1 << 5)
+#define CH341_BIT_RTS BIT(6)
+#define CH341_BIT_DTR BIT(5)
/******************************/
/* interrupt pipe definitions */
@@ -40,8 +42,10 @@
/* 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 */
+/*
+ * 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
@@ -83,6 +87,7 @@
#define CH341_QUIRK_LIMITED_PRESCALER BIT(0)
#define CH341_QUIRK_SIMULATE_BREAK BIT(1)
+#define CH341_QUIRK_INVERTED_BIT7 BIT(2)
static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x1a86, 0x5523) },
@@ -97,7 +102,7 @@
struct ch341_private {
spinlock_t lock; /* access lock */
- unsigned baud_rate; /* set baud rate */
+ unsigned int baud_rate; /* set baud rate */
u8 mcr;
u8 msr;
u8 lcr;
@@ -106,12 +111,21 @@
u8 version;
unsigned long break_end;
+
+ struct dentry *debugfs;
+ unsigned int dbg_speed;
+ int dbg_divisor;
+ unsigned int dbg_actual;
};
static void ch341_set_termios(struct tty_struct *tty,
struct usb_serial_port *port,
const struct ktermios *old_termios);
+static void ch341_debugfs_init_port(struct usb_serial_port *port,
+ struct ch341_private *priv);
+static void ch341_debugfs_remove_port(struct ch341_private *priv);
+
static int ch341_control_out(struct usb_device *dev, u8 request,
u16 value, u16 index)
{
@@ -120,10 +134,11 @@
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)
+ r = usb_control_msg_send(dev, 0, request,
+ USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
+ value, index, NULL, 0, DEFAULT_TIMEOUT,
+ GFP_KERNEL);
+ if (r)
dev_err(&dev->dev, "failed to send control message: %d\n", r);
return r;
@@ -131,7 +146,7 @@
static int ch341_control_in(struct usb_device *dev,
u8 request, u16 value, u16 index,
- char *buf, unsigned bufsize)
+ char *buf, unsigned int bufsize)
{
int r;
@@ -155,7 +170,7 @@
#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[] = {
+static const unsigned int ch341_min_rates[] = {
CH341_MIN_RATE(0),
CH341_MIN_RATE(1),
CH341_MIN_RATE(2),
@@ -176,7 +191,7 @@
* 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)
+static int ch341_get_divisor(struct ch341_private *priv, unsigned int speed)
{
unsigned int fact, div, clk_div;
bool force_fact0 = false;
@@ -242,7 +257,7 @@
static int ch341_set_baudrate_lcr(struct usb_device *dev,
struct ch341_private *priv,
- speed_t baud_rate, u8 lcr)
+ unsigned int baud_rate, u8 lcr)
{
int val;
int r;
@@ -256,12 +271,10 @@
/*
* 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.
+ * 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)
+ if (!(priv->quirks & CH341_QUIRK_INVERTED_BIT7))
val |= BIT(7);
r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
@@ -326,6 +339,15 @@
priv->version = buffer[0];
dev_dbg(&dev->dev, "Chip version: 0x%02x\n", priv->version);
+ /*
+ * 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, so it must not be
+ * set on those devices.
+ */
+ if (priv->version <= 0x27)
+ priv->quirks |= CH341_QUIRK_INVERTED_BIT7;
+
r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
if (r < 0)
return r;
@@ -403,6 +425,8 @@
if (r < 0)
goto error;
+ ch341_debugfs_init_port(port, priv);
+
return 0;
error: kfree(priv);
@@ -414,12 +438,14 @@
struct ch341_private *priv;
priv = usb_get_serial_port_data(port);
+ ch341_debugfs_remove_port(priv);
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;
@@ -446,7 +472,6 @@
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)
{
@@ -512,7 +537,7 @@
const struct ktermios *old_termios)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
- unsigned baud_rate;
+ unsigned int baud_rate;
unsigned long flags;
u8 lcr;
int r;
@@ -552,14 +577,12 @@
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);
+ 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->baud_rate = baud_rate;
priv->lcr = lcr;
}
}
@@ -601,8 +624,9 @@
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);
+ 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",
@@ -625,7 +649,8 @@
*
* 11 bits = 1 start, 8 data, 1 stop, 1 margin
*/
- priv->break_end = jiffies + (11 * HZ / CH341_MIN_BPS);
+ WRITE_ONCE(priv->break_end,
+ jiffies + (11 * HZ / CH341_MIN_BPS));
return 0;
}
@@ -634,9 +659,10 @@
now = jiffies;
- if (time_before(now, priv->break_end)) {
+ delay = READ_ONCE(priv->break_end);
+ if (time_before(now, delay)) {
/* Wait until NUL byte is written */
- delay = priv->break_end - now;
+ delay -= now;
dev_dbg(&port->dev,
"wait %d ms while transmitting NUL byte at %u baud\n",
jiffies_to_msecs(delay), CH341_MIN_BPS);
@@ -647,7 +673,7 @@
restore:
/* Restore original baud rate */
r2 = ch341_set_baudrate_lcr(port->serial->dev, priv, priv->baud_rate,
- priv->lcr);
+ priv->lcr);
if (r2 < 0) {
dev_err(&port->dev,
"restoring original baud rate of %u failed: %d\n",
@@ -671,10 +697,10 @@
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);
+ ch341_break_reg, 0, break_reg, 2);
if (r) {
dev_err(&port->dev, "%s - USB control read error (%d)\n",
- __func__, r);
+ __func__, r);
if (r > 0)
r = -EIO;
return r;
@@ -694,10 +720,10 @@
__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);
+ ch341_break_reg, reg_contents);
if (r < 0) {
dev_err(&port->dev, "%s - USB control write error (%d)\n",
- __func__, r);
+ __func__, r);
return r;
}
@@ -728,7 +754,7 @@
}
static void ch341_update_status(struct usb_serial_port *port,
- unsigned char *data, size_t len)
+ unsigned char *data, size_t len)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
struct tty_struct *tty;
@@ -763,7 +789,7 @@
tty = tty_port_tty_get(&port->port);
if (tty) {
usb_serial_handle_dcd_change(port, tty,
- status & CH341_BIT_DCD);
+ status & CH341_BIT_DCD);
tty_kref_put(tty);
}
}
@@ -842,7 +868,12 @@
return 0;
/* reconfigure ch341 serial port after bus-reset */
- ch341_configure(serial->dev, priv);
+ ret = ch341_configure(serial->dev, priv);
+ if (ret) {
+ dev_err(&port->dev, "failed to reconfigure after bus reset: %d\n",
+ ret);
+ return ret;
+ }
if (tty_port_initialized(&port->port)) {
ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
@@ -862,6 +893,139 @@
return usb_serial_generic_resume(serial);
}
+/* -------------------------------------------------------------------------- */
+/* debugfs interface */
+/* -------------------------------------------------------------------------- */
+
+static struct dentry *ch341_debugfs_root;
+
+/*
+ * Decode the raw value returned by ch341_get_divisor() back into the actual
+ * line speed, using the inverse of the formula in that function.
+ */
+static unsigned int ch341_decode_rate(int val)
+{
+ unsigned int ps = val & 0x03;
+ unsigned int fact = (val >> 2) & 1;
+ unsigned int div = 0x100 - (val >> 8);
+ unsigned int clk_div = 1 << (12 - 3 * ps - fact);
+
+ return CH341_CLKRATE / (clk_div * div);
+}
+
+static int ch341_debugfs_info_show(struct seq_file *m, void *v)
+{
+ struct ch341_private *priv = m->private;
+ unsigned long flags;
+ u8 mcr, msr;
+
+ spin_lock_irqsave(&priv->lock, flags);
+ mcr = priv->mcr;
+ msr = priv->msr;
+ spin_unlock_irqrestore(&priv->lock, flags);
+
+ seq_printf(m, "version: 0x%02x\n", priv->version);
+ seq_printf(m, "quirks: 0x%04lx\n", priv->quirks);
+ seq_printf(m, "baud: %u\n", priv->baud_rate);
+ seq_printf(m, "mcr: 0x%02x\n", mcr);
+ seq_printf(m, "msr: 0x%02x\n", msr);
+
+ return 0;
+}
+
+static int ch341_debugfs_info_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, ch341_debugfs_info_show, inode->i_private);
+}
+
+static const struct file_operations ch341_debugfs_info_fops = {
+ .open = ch341_debugfs_info_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static int ch341_debugfs_baud_show(struct seq_file *m, void *v)
+{
+ struct ch341_private *priv = m->private;
+
+ seq_printf(m, "requested: %u\n", priv->dbg_speed);
+ seq_printf(m, "divisor: 0x%04x\n", priv->dbg_divisor);
+ seq_printf(m, "actual: %u\n", priv->dbg_actual);
+
+ return 0;
+}
+
+static int ch341_debugfs_baud_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, ch341_debugfs_baud_show, inode->i_private);
+}
+
+/*
+ * Writing a line speed to this file runs the divisor calculation and reports
+ * the resulting raw divisor value and the achieved rate. This allows the
+ * formula in ch341_get_divisor() to be verified from userspace without any
+ * hardware.
+ */
+static ssize_t ch341_debugfs_baud_write(struct file *file,
+ const char __user *buf, size_t count,
+ loff_t *ppos)
+{
+ struct seq_file *seq = file->private_data;
+ struct ch341_private *priv = seq->private;
+ char kbuf[16];
+ unsigned long speed;
+ int divisor;
+ int ret;
+
+ if (count >= sizeof(kbuf))
+ return -EINVAL;
+
+ ret = simple_write_to_buffer(kbuf, sizeof(kbuf) - 1, ppos, buf, count);
+ if (ret < 0)
+ return ret;
+ kbuf[ret] = '\0';
+
+ ret = kstrtoul(kbuf, 10, &speed);
+ if (ret)
+ return ret;
+
+ divisor = ch341_get_divisor(priv, speed);
+ if (divisor < 0)
+ return -EINVAL;
+
+ priv->dbg_speed = speed;
+ priv->dbg_divisor = divisor;
+ priv->dbg_actual = ch341_decode_rate(divisor);
+
+ return count;
+}
+
+static const struct file_operations ch341_debugfs_baud_fops = {
+ .open = ch341_debugfs_baud_open,
+ .read = seq_read,
+ .write = ch341_debugfs_baud_write,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static void ch341_debugfs_init_port(struct usb_serial_port *port,
+ struct ch341_private *priv)
+{
+ priv->debugfs = debugfs_create_dir(dev_name(&port->dev),
+ ch341_debugfs_root);
+ debugfs_create_file("info", 0444, priv->debugfs, priv,
+ &ch341_debugfs_info_fops);
+ debugfs_create_file("baud", 0644, priv->debugfs, priv,
+ &ch341_debugfs_baud_fops);
+}
+
+static void ch341_debugfs_remove_port(struct ch341_private *priv)
+{
+ debugfs_remove_recursive(priv->debugfs);
+ priv->debugfs = NULL;
+}
+
static struct usb_serial_driver ch341_device = {
.driver = {
.name = "ch341-uart",
@@ -887,7 +1051,28 @@
&ch341_device, NULL
};
-module_usb_serial_driver(serial_drivers, id_table);
+static int __init ch341_init(void)
+{
+ int r;
+
+ ch341_debugfs_root = debugfs_create_dir("ch341-uart", NULL);
+
+ r = usb_serial_register_drivers(serial_drivers, KBUILD_MODNAME,
+ id_table);
+ if (r)
+ debugfs_remove_recursive(ch341_debugfs_root);
+
+ return r;
+}
+
+static void __exit ch341_exit(void)
+{
+ usb_serial_deregister_drivers(serial_drivers);
+ debugfs_remove_recursive(ch341_debugfs_root);
+}
+
+module_init(ch341_init);
+module_exit(ch341_exit);
MODULE_DESCRIPTION("Winchiphead CH341 USB Serial driver");
MODULE_LICENSE("GPL v2");
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH] usb: serial: ch341: add debugfs interface and clean up
@ 2026-08-05 15:31 Vegom Doster
2026-08-06 4:41 ` Greg KH
0 siblings, 1 reply; 4+ messages in thread
From: Vegom Doster @ 2026-08-05 15:31 UTC (permalink / raw)
To: linux-usb; +Cc: johan
[-- Attachment #1: Type: text/plain, Size: 1048 bytes --]
This patch adds a debugfs interface for the CH341 driver, allowing runtime
inspection of chip version, quirks, and line status. It also adds a 'baud'
file to test the divisor calculation without hardware.
The patch also cleans up magic numbers, removes duplicate code, and fixes
several issues:
- Replace obsolete usb_control_msg() with usb_control_msg_send/recv
- Convert version>0x27 hack to proper CH341_QUIRK_INVERTED_BIT7
- Fix baud_rate update in ch341_set_termios (only on success)
- Use READ_ONCE/WRITE_ONCE for break_end
- Fix error handling in ch341_reset_resume
- Add debugfs interface for diagnostics
No functional changes are made to the driver's operation.
Tested on Arch Linux with Arduino Uno (CH340C, 1a86:7523):
- checkpatch: 0 errors, 0 warnings, 0 checks
- DTR/RTS (tiocmget/set): PASS
- Echo at 9600 and 115200 baud: PASS (byte-per-byte)
- Divisor formula for 15 speeds (300..3000000): PASS (error ≤0.16%)
- debugfs: tested with custom test script
Signed-off-by: nerolocker <vegomdoster@gmail.com>
[-- Attachment #2: ch341-debugfs.patch --]
[-- Type: text/x-patch, Size: 13803 bytes --]
--- ch341_orig.c 2026-08-05 20:21:58.742065698 +0500
+++ ch341.c 2026-08-05 20:16:58.012117521 +0500
@@ -3,6 +3,7 @@
* Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
* Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
* Copyright 2009, Boris Hajduk <boris@hajduk.org>
+ * Copyright 2026, nerolocker <vegomdoster@gmail.com>
*
* ch341.c implements a serial port driver for the Winchiphead CH341.
*
@@ -16,6 +17,7 @@
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/slab.h>
+#include <linux/debugfs.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
@@ -25,8 +27,8 @@
#define DEFAULT_TIMEOUT 1000
/* flags for IO-Bits */
-#define CH341_BIT_RTS (1 << 6)
-#define CH341_BIT_DTR (1 << 5)
+#define CH341_BIT_RTS BIT(6)
+#define CH341_BIT_DTR BIT(5)
/******************************/
/* interrupt pipe definitions */
@@ -40,8 +42,10 @@
/* 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 */
+/*
+ * 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
@@ -83,6 +87,7 @@
#define CH341_QUIRK_LIMITED_PRESCALER BIT(0)
#define CH341_QUIRK_SIMULATE_BREAK BIT(1)
+#define CH341_QUIRK_INVERTED_BIT7 BIT(2)
static const struct usb_device_id id_table[] = {
{ USB_DEVICE(0x1a86, 0x5523) },
@@ -97,7 +102,7 @@
struct ch341_private {
spinlock_t lock; /* access lock */
- unsigned baud_rate; /* set baud rate */
+ unsigned int baud_rate; /* set baud rate */
u8 mcr;
u8 msr;
u8 lcr;
@@ -106,12 +111,21 @@
u8 version;
unsigned long break_end;
+
+ struct dentry *debugfs;
+ unsigned int dbg_speed;
+ int dbg_divisor;
+ unsigned int dbg_actual;
};
static void ch341_set_termios(struct tty_struct *tty,
struct usb_serial_port *port,
const struct ktermios *old_termios);
+static void ch341_debugfs_init_port(struct usb_serial_port *port,
+ struct ch341_private *priv);
+static void ch341_debugfs_remove_port(struct ch341_private *priv);
+
static int ch341_control_out(struct usb_device *dev, u8 request,
u16 value, u16 index)
{
@@ -120,10 +134,11 @@
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)
+ r = usb_control_msg_send(dev, 0, request,
+ USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
+ value, index, NULL, 0, DEFAULT_TIMEOUT,
+ GFP_KERNEL);
+ if (r)
dev_err(&dev->dev, "failed to send control message: %d\n", r);
return r;
@@ -131,7 +146,7 @@
static int ch341_control_in(struct usb_device *dev,
u8 request, u16 value, u16 index,
- char *buf, unsigned bufsize)
+ char *buf, unsigned int bufsize)
{
int r;
@@ -155,7 +170,7 @@
#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[] = {
+static const unsigned int ch341_min_rates[] = {
CH341_MIN_RATE(0),
CH341_MIN_RATE(1),
CH341_MIN_RATE(2),
@@ -176,7 +191,7 @@
* 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)
+static int ch341_get_divisor(struct ch341_private *priv, unsigned int speed)
{
unsigned int fact, div, clk_div;
bool force_fact0 = false;
@@ -242,7 +257,7 @@
static int ch341_set_baudrate_lcr(struct usb_device *dev,
struct ch341_private *priv,
- speed_t baud_rate, u8 lcr)
+ unsigned int baud_rate, u8 lcr)
{
int val;
int r;
@@ -256,12 +271,10 @@
/*
* 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.
+ * 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)
+ if (!(priv->quirks & CH341_QUIRK_INVERTED_BIT7))
val |= BIT(7);
r = ch341_control_out(dev, CH341_REQ_WRITE_REG,
@@ -326,6 +339,15 @@
priv->version = buffer[0];
dev_dbg(&dev->dev, "Chip version: 0x%02x\n", priv->version);
+ /*
+ * 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, so it must not be
+ * set on those devices.
+ */
+ if (priv->version <= 0x27)
+ priv->quirks |= CH341_QUIRK_INVERTED_BIT7;
+
r = ch341_control_out(dev, CH341_REQ_SERIAL_INIT, 0, 0);
if (r < 0)
return r;
@@ -403,6 +425,8 @@
if (r < 0)
goto error;
+ ch341_debugfs_init_port(port, priv);
+
return 0;
error: kfree(priv);
@@ -414,12 +438,14 @@
struct ch341_private *priv;
priv = usb_get_serial_port_data(port);
+ ch341_debugfs_remove_port(priv);
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;
@@ -446,7 +472,6 @@
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)
{
@@ -512,7 +537,7 @@
const struct ktermios *old_termios)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
- unsigned baud_rate;
+ unsigned int baud_rate;
unsigned long flags;
u8 lcr;
int r;
@@ -552,14 +577,12 @@
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);
+ 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->baud_rate = baud_rate;
priv->lcr = lcr;
}
}
@@ -601,8 +624,9 @@
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);
+ 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",
@@ -625,7 +649,8 @@
*
* 11 bits = 1 start, 8 data, 1 stop, 1 margin
*/
- priv->break_end = jiffies + (11 * HZ / CH341_MIN_BPS);
+ WRITE_ONCE(priv->break_end,
+ jiffies + (11 * HZ / CH341_MIN_BPS));
return 0;
}
@@ -634,9 +659,10 @@
now = jiffies;
- if (time_before(now, priv->break_end)) {
+ delay = READ_ONCE(priv->break_end);
+ if (time_before(now, delay)) {
/* Wait until NUL byte is written */
- delay = priv->break_end - now;
+ delay -= now;
dev_dbg(&port->dev,
"wait %d ms while transmitting NUL byte at %u baud\n",
jiffies_to_msecs(delay), CH341_MIN_BPS);
@@ -647,7 +673,7 @@
restore:
/* Restore original baud rate */
r2 = ch341_set_baudrate_lcr(port->serial->dev, priv, priv->baud_rate,
- priv->lcr);
+ priv->lcr);
if (r2 < 0) {
dev_err(&port->dev,
"restoring original baud rate of %u failed: %d\n",
@@ -671,10 +697,10 @@
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);
+ ch341_break_reg, 0, break_reg, 2);
if (r) {
dev_err(&port->dev, "%s - USB control read error (%d)\n",
- __func__, r);
+ __func__, r);
if (r > 0)
r = -EIO;
return r;
@@ -694,10 +720,10 @@
__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);
+ ch341_break_reg, reg_contents);
if (r < 0) {
dev_err(&port->dev, "%s - USB control write error (%d)\n",
- __func__, r);
+ __func__, r);
return r;
}
@@ -728,7 +754,7 @@
}
static void ch341_update_status(struct usb_serial_port *port,
- unsigned char *data, size_t len)
+ unsigned char *data, size_t len)
{
struct ch341_private *priv = usb_get_serial_port_data(port);
struct tty_struct *tty;
@@ -763,7 +789,7 @@
tty = tty_port_tty_get(&port->port);
if (tty) {
usb_serial_handle_dcd_change(port, tty,
- status & CH341_BIT_DCD);
+ status & CH341_BIT_DCD);
tty_kref_put(tty);
}
}
@@ -842,7 +868,12 @@
return 0;
/* reconfigure ch341 serial port after bus-reset */
- ch341_configure(serial->dev, priv);
+ ret = ch341_configure(serial->dev, priv);
+ if (ret) {
+ dev_err(&port->dev, "failed to reconfigure after bus reset: %d\n",
+ ret);
+ return ret;
+ }
if (tty_port_initialized(&port->port)) {
ret = usb_submit_urb(port->interrupt_in_urb, GFP_NOIO);
@@ -862,6 +893,139 @@
return usb_serial_generic_resume(serial);
}
+/* -------------------------------------------------------------------------- */
+/* debugfs interface */
+/* -------------------------------------------------------------------------- */
+
+static struct dentry *ch341_debugfs_root;
+
+/*
+ * Decode the raw value returned by ch341_get_divisor() back into the actual
+ * line speed, using the inverse of the formula in that function.
+ */
+static unsigned int ch341_decode_rate(int val)
+{
+ unsigned int ps = val & 0x03;
+ unsigned int fact = (val >> 2) & 1;
+ unsigned int div = 0x100 - (val >> 8);
+ unsigned int clk_div = 1 << (12 - 3 * ps - fact);
+
+ return CH341_CLKRATE / (clk_div * div);
+}
+
+static int ch341_debugfs_info_show(struct seq_file *m, void *v)
+{
+ struct ch341_private *priv = m->private;
+ unsigned long flags;
+ u8 mcr, msr;
+
+ spin_lock_irqsave(&priv->lock, flags);
+ mcr = priv->mcr;
+ msr = priv->msr;
+ spin_unlock_irqrestore(&priv->lock, flags);
+
+ seq_printf(m, "version: 0x%02x\n", priv->version);
+ seq_printf(m, "quirks: 0x%04lx\n", priv->quirks);
+ seq_printf(m, "baud: %u\n", priv->baud_rate);
+ seq_printf(m, "mcr: 0x%02x\n", mcr);
+ seq_printf(m, "msr: 0x%02x\n", msr);
+
+ return 0;
+}
+
+static int ch341_debugfs_info_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, ch341_debugfs_info_show, inode->i_private);
+}
+
+static const struct file_operations ch341_debugfs_info_fops = {
+ .open = ch341_debugfs_info_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static int ch341_debugfs_baud_show(struct seq_file *m, void *v)
+{
+ struct ch341_private *priv = m->private;
+
+ seq_printf(m, "requested: %u\n", priv->dbg_speed);
+ seq_printf(m, "divisor: 0x%04x\n", priv->dbg_divisor);
+ seq_printf(m, "actual: %u\n", priv->dbg_actual);
+
+ return 0;
+}
+
+static int ch341_debugfs_baud_open(struct inode *inode, struct file *file)
+{
+ return single_open(file, ch341_debugfs_baud_show, inode->i_private);
+}
+
+/*
+ * Writing a line speed to this file runs the divisor calculation and reports
+ * the resulting raw divisor value and the achieved rate. This allows the
+ * formula in ch341_get_divisor() to be verified from userspace without any
+ * hardware.
+ */
+static ssize_t ch341_debugfs_baud_write(struct file *file,
+ const char __user *buf, size_t count,
+ loff_t *ppos)
+{
+ struct seq_file *seq = file->private_data;
+ struct ch341_private *priv = seq->private;
+ char kbuf[16];
+ unsigned long speed;
+ int divisor;
+ int ret;
+
+ if (count >= sizeof(kbuf))
+ return -EINVAL;
+
+ ret = simple_write_to_buffer(kbuf, sizeof(kbuf) - 1, ppos, buf, count);
+ if (ret < 0)
+ return ret;
+ kbuf[ret] = '\0';
+
+ ret = kstrtoul(kbuf, 10, &speed);
+ if (ret)
+ return ret;
+
+ divisor = ch341_get_divisor(priv, speed);
+ if (divisor < 0)
+ return -EINVAL;
+
+ priv->dbg_speed = speed;
+ priv->dbg_divisor = divisor;
+ priv->dbg_actual = ch341_decode_rate(divisor);
+
+ return count;
+}
+
+static const struct file_operations ch341_debugfs_baud_fops = {
+ .open = ch341_debugfs_baud_open,
+ .read = seq_read,
+ .write = ch341_debugfs_baud_write,
+ .llseek = seq_lseek,
+ .release = single_release,
+};
+
+static void ch341_debugfs_init_port(struct usb_serial_port *port,
+ struct ch341_private *priv)
+{
+ priv->debugfs = debugfs_create_dir(dev_name(&port->dev),
+ ch341_debugfs_root);
+ debugfs_create_file("info", 0444, priv->debugfs, priv,
+ &ch341_debugfs_info_fops);
+ debugfs_create_file("baud", 0644, priv->debugfs, priv,
+ &ch341_debugfs_baud_fops);
+}
+
+static void ch341_debugfs_remove_port(struct ch341_private *priv)
+{
+ debugfs_remove_recursive(priv->debugfs);
+ priv->debugfs = NULL;
+}
+
static struct usb_serial_driver ch341_device = {
.driver = {
.name = "ch341-uart",
@@ -887,7 +1051,28 @@
&ch341_device, NULL
};
-module_usb_serial_driver(serial_drivers, id_table);
+static int __init ch341_init(void)
+{
+ int r;
+
+ ch341_debugfs_root = debugfs_create_dir("ch341-uart", NULL);
+
+ r = usb_serial_register_drivers(serial_drivers, KBUILD_MODNAME,
+ id_table);
+ if (r)
+ debugfs_remove_recursive(ch341_debugfs_root);
+
+ return r;
+}
+
+static void __exit ch341_exit(void)
+{
+ usb_serial_deregister_drivers(serial_drivers);
+ debugfs_remove_recursive(ch341_debugfs_root);
+}
+
+module_init(ch341_init);
+module_exit(ch341_exit);
MODULE_DESCRIPTION("Winchiphead CH341 USB Serial driver");
MODULE_LICENSE("GPL v2");
[-- Attachment #3: ch341.c --]
[-- Type: text/x-csrc, Size: 28095 bytes --]
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright 2007, Frank A Kingswood <frank@kingswood-consulting.co.uk>
* Copyright 2007, Werner Cornelius <werner@cornelius-consult.de>
* Copyright 2009, Boris Hajduk <boris@hajduk.org>
* Copyright 2026, nerolocker <vegomdoster@gmail.com>
*
* 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 <linux/kernel.h>
#include <linux/tty.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/debugfs.h>
#include <linux/usb.h>
#include <linux/usb/serial.h>
#include <linux/serial.h>
#include <linux/unaligned.h>
#define DEFAULT_BAUD_RATE 9600
#define DEFAULT_TIMEOUT 1000
/* flags for IO-Bits */
#define CH341_BIT_RTS BIT(6)
#define CH341_BIT_DTR BIT(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_REG_FLOW_CTL 0x27
#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_FLOW_CTL_NONE 0x00
#define CH341_FLOW_CTL_RTSCTS 0x01
#define CH341_QUIRK_LIMITED_PRESCALER BIT(0)
#define CH341_QUIRK_SIMULATE_BREAK BIT(1)
#define CH341_QUIRK_INVERTED_BIT7 BIT(2)
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 int baud_rate; /* set baud rate */
u8 mcr;
u8 msr;
u8 lcr;
unsigned long quirks;
u8 version;
unsigned long break_end;
struct dentry *debugfs;
unsigned int dbg_speed;
int dbg_divisor;
unsigned int dbg_actual;
};
static void ch341_set_termios(struct tty_struct *tty,
struct usb_serial_port *port,
const struct ktermios *old_termios);
static void ch341_debugfs_init_port(struct usb_serial_port *port,
struct ch341_private *priv);
static void ch341_debugfs_remove_port(struct ch341_private *priv);
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_send(dev, 0, request,
USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_OUT,
value, index, NULL, 0, DEFAULT_TIMEOUT,
GFP_KERNEL);
if (r)
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 int 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 unsigned int 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, unsigned int 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,
unsigned int 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->quirks & CH341_QUIRK_INVERTED_BIT7))
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);
/*
* 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, so it must not be
* set on those devices.
*/
if (priv->version <= 0x27)
priv->quirks |= CH341_QUIRK_INVERTED_BIT7;
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_obj(struct ch341_private);
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;
ch341_debugfs_init_port(port, priv);
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);
ch341_debugfs_remove_port(priv);
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;
}
static void ch341_set_flow_control(struct tty_struct *tty,
struct usb_serial_port *port,
const struct ktermios *old_termios)
{
u16 flow_ctl;
int r;
if (C_CRTSCTS(tty))
flow_ctl = CH341_FLOW_CTL_RTSCTS;
else
flow_ctl = CH341_FLOW_CTL_NONE;
r = ch341_control_out(port->serial->dev,
CH341_REQ_WRITE_REG,
(CH341_REG_FLOW_CTL << 8) | CH341_REG_FLOW_CTL,
(flow_ctl << 8) | flow_ctl);
if (r < 0 && old_termios) {
tty->termios.c_cflag &= ~CRTSCTS;
tty->termios.c_cflag |= (old_termios->c_cflag & CRTSCTS);
}
}
/* 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 int 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) {
r = ch341_set_baudrate_lcr(port->serial->dev, priv,
baud_rate, lcr);
if (r < 0 && old_termios) {
tty_termios_copy_hw(&tty->termios, old_termios);
} else if (r == 0) {
priv->baud_rate = baud_rate;
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);
ch341_set_flow_control(tty, port, old_termios);
}
/*
* 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
*/
WRITE_ONCE(priv->break_end,
jiffies + (11 * HZ / CH341_MIN_BPS));
return 0;
}
dev_dbg(&port->dev, "leave break state requested\n");
now = jiffies;
delay = READ_ONCE(priv->break_end);
if (time_before(now, delay)) {
/* Wait until NUL byte is written */
delay -= 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 u16 ch341_break_reg = (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);
u16 reg_contents;
u8 break_reg[2];
int r;
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 */
ret = ch341_configure(serial->dev, priv);
if (ret) {
dev_err(&port->dev, "failed to reconfigure after bus reset: %d\n",
ret);
return ret;
}
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);
}
/* -------------------------------------------------------------------------- */
/* debugfs interface */
/* -------------------------------------------------------------------------- */
static struct dentry *ch341_debugfs_root;
/*
* Decode the raw value returned by ch341_get_divisor() back into the actual
* line speed, using the inverse of the formula in that function.
*/
static unsigned int ch341_decode_rate(int val)
{
unsigned int ps = val & 0x03;
unsigned int fact = (val >> 2) & 1;
unsigned int div = 0x100 - (val >> 8);
unsigned int clk_div = 1 << (12 - 3 * ps - fact);
return CH341_CLKRATE / (clk_div * div);
}
static int ch341_debugfs_info_show(struct seq_file *m, void *v)
{
struct ch341_private *priv = m->private;
unsigned long flags;
u8 mcr, msr;
spin_lock_irqsave(&priv->lock, flags);
mcr = priv->mcr;
msr = priv->msr;
spin_unlock_irqrestore(&priv->lock, flags);
seq_printf(m, "version: 0x%02x\n", priv->version);
seq_printf(m, "quirks: 0x%04lx\n", priv->quirks);
seq_printf(m, "baud: %u\n", priv->baud_rate);
seq_printf(m, "mcr: 0x%02x\n", mcr);
seq_printf(m, "msr: 0x%02x\n", msr);
return 0;
}
static int ch341_debugfs_info_open(struct inode *inode, struct file *file)
{
return single_open(file, ch341_debugfs_info_show, inode->i_private);
}
static const struct file_operations ch341_debugfs_info_fops = {
.open = ch341_debugfs_info_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static int ch341_debugfs_baud_show(struct seq_file *m, void *v)
{
struct ch341_private *priv = m->private;
seq_printf(m, "requested: %u\n", priv->dbg_speed);
seq_printf(m, "divisor: 0x%04x\n", priv->dbg_divisor);
seq_printf(m, "actual: %u\n", priv->dbg_actual);
return 0;
}
static int ch341_debugfs_baud_open(struct inode *inode, struct file *file)
{
return single_open(file, ch341_debugfs_baud_show, inode->i_private);
}
/*
* Writing a line speed to this file runs the divisor calculation and reports
* the resulting raw divisor value and the achieved rate. This allows the
* formula in ch341_get_divisor() to be verified from userspace without any
* hardware.
*/
static ssize_t ch341_debugfs_baud_write(struct file *file,
const char __user *buf, size_t count,
loff_t *ppos)
{
struct seq_file *seq = file->private_data;
struct ch341_private *priv = seq->private;
char kbuf[16];
unsigned long speed;
int divisor;
int ret;
if (count >= sizeof(kbuf))
return -EINVAL;
ret = simple_write_to_buffer(kbuf, sizeof(kbuf) - 1, ppos, buf, count);
if (ret < 0)
return ret;
kbuf[ret] = '\0';
ret = kstrtoul(kbuf, 10, &speed);
if (ret)
return ret;
divisor = ch341_get_divisor(priv, speed);
if (divisor < 0)
return -EINVAL;
priv->dbg_speed = speed;
priv->dbg_divisor = divisor;
priv->dbg_actual = ch341_decode_rate(divisor);
return count;
}
static const struct file_operations ch341_debugfs_baud_fops = {
.open = ch341_debugfs_baud_open,
.read = seq_read,
.write = ch341_debugfs_baud_write,
.llseek = seq_lseek,
.release = single_release,
};
static void ch341_debugfs_init_port(struct usb_serial_port *port,
struct ch341_private *priv)
{
priv->debugfs = debugfs_create_dir(dev_name(&port->dev),
ch341_debugfs_root);
debugfs_create_file("info", 0444, priv->debugfs, priv,
&ch341_debugfs_info_fops);
debugfs_create_file("baud", 0644, priv->debugfs, priv,
&ch341_debugfs_baud_fops);
}
static void ch341_debugfs_remove_port(struct ch341_private *priv)
{
debugfs_remove_recursive(priv->debugfs);
priv->debugfs = NULL;
}
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
};
static int __init ch341_init(void)
{
int r;
ch341_debugfs_root = debugfs_create_dir("ch341-uart", NULL);
r = usb_serial_register_drivers(serial_drivers, KBUILD_MODNAME,
id_table);
if (r)
debugfs_remove_recursive(ch341_debugfs_root);
return r;
}
static void __exit ch341_exit(void)
{
usb_serial_deregister_drivers(serial_drivers);
debugfs_remove_recursive(ch341_debugfs_root);
}
module_init(ch341_init);
module_exit(ch341_exit);
MODULE_DESCRIPTION("Winchiphead CH341 USB Serial driver");
MODULE_LICENSE("GPL v2");
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] usb: serial: ch341: add debugfs interface and clean up
2026-08-05 15:28 ` Vegom Doster
@ 2026-08-06 4:40 ` Greg KH
0 siblings, 0 replies; 4+ messages in thread
From: Greg KH @ 2026-08-06 4:40 UTC (permalink / raw)
To: Vegom Doster; +Cc: linux-usb
On Wed, Aug 05, 2026 at 08:28:00PM +0500, Vegom Doster wrote:
> On Wed, Aug 5, 2026 at 8:27 PM Vegom Doster <vegomdoster@gmail.com> wrote:
>
> > This patch adds a debugfs interface for the CH341 driver, allowing runtime
> > inspection of chip version, quirks, and line status. It also adds a 'baud'
> > file to test the divisor calculation without hardware.
> >
> > The patch also cleans up magic numbers, removes duplicate code, and fixes
> > several issues:
> > - Replace obsolete usb_control_msg() with usb_control_msg_send/recv
> > - Convert version>0x27 hack to proper CH341_QUIRK_INVERTED_BIT7
> > - Fix baud_rate update in ch341_set_termios (only on success)
> > - Use READ_ONCE/WRITE_ONCE for break_end
> > - Fix error handling in ch341_reset_resume
> > - Add debugfs interface for diagnostics
> >
> > No functional changes are made to the driver's operation.
> >
> > Tested on Arch Linux with Arduino Uno (CH340C, 1a86:7523):
> > - checkpatch: 0 errors, 0 warnings, 0 checks
> > - DTR/RTS (tiocmget/set): PASS
> > - Echo at 9600 and 115200 baud: PASS (byte-per-byte)
> > - Divisor formula for 15 speeds (300..3000000): PASS (error ≤0.16%)
> > - debugfs: tested with custom test script
> >
> > Signed-off-by: nerolocker <vegomdoster@gmail.com>
This shouldn't be quoted, and you need a real name for the signed-off-by
line.
> >
> // SPDX-License-Identifier: GPL-2.0
This isn't a diff, but rather the whole file.
Perhaps take a look at the "how to write a kernel patch" tutorial on
kernelnewbies.org first?
Also, obviously, you have to break this up into smaller pieces to even
be able to get it reviewed :)
And finally, why add a debugfs file at all? What is it going to be used
for and why is it only needed now, after the driver is very stable?
thanks,
greg k-h
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] usb: serial: ch341: add debugfs interface and clean up
2026-08-05 15:31 [PATCH] usb: serial: ch341: add debugfs interface and clean up Vegom Doster
@ 2026-08-06 4:41 ` Greg KH
0 siblings, 0 replies; 4+ messages in thread
From: Greg KH @ 2026-08-06 4:41 UTC (permalink / raw)
To: Vegom Doster; +Cc: linux-usb, johan
On Wed, Aug 05, 2026 at 08:31:00PM +0500, Vegom Doster wrote:
> This patch adds a debugfs interface for the CH341 driver, allowing runtime
> inspection of chip version, quirks, and line status. It also adds a 'baud'
> file to test the divisor calculation without hardware.
>
> The patch also cleans up magic numbers, removes duplicate code, and fixes
> several issues:
> - Replace obsolete usb_control_msg() with usb_control_msg_send/recv
> - Convert version>0x27 hack to proper CH341_QUIRK_INVERTED_BIT7
> - Fix baud_rate update in ch341_set_termios (only on success)
> - Use READ_ONCE/WRITE_ONCE for break_end
> - Fix error handling in ch341_reset_resume
> - Add debugfs interface for diagnostics
>
> No functional changes are made to the driver's operation.
>
> Tested on Arch Linux with Arduino Uno (CH340C, 1a86:7523):
> - checkpatch: 0 errors, 0 warnings, 0 checks
> - DTR/RTS (tiocmget/set): PASS
> - Echo at 9600 and 115200 baud: PASS (byte-per-byte)
> - Divisor formula for 15 speeds (300..3000000): PASS (error ≤0.16%)
> - debugfs: tested with custom test script
>
> Signed-off-by: nerolocker <vegomdoster@gmail.com>
Better, but my bot says:
--------
Hi,
This is the friendly patch-bot of Greg Kroah-Hartman. You have sent him
a patch that has triggered this response. He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created. Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.
You are receiving this message because of the following common error(s)
as indicated below:
- Your patch did many different things all at once, making it difficult
to review. All Linux kernel patches need to only do one thing at a
time. If you need to do multiple things (such as clean up all coding
style issues in a file/driver), do it in a sequence of patches, each
one doing only one thing. This will make it easier to review the
patches to ensure that they are correct, and to help alleviate any
merge issues that larger patches can cause.
- It looks like you did not use your "real" name for the patch on either
the Signed-off-by: line, or the From: line (both of which have to
match). Please read the kernel file,
Documentation/process/submitting-patches.rst for how to do this
correctly.
- This looks like a new version of a previously submitted patch, but you
did not list below the --- line any changes from the previous version.
Please read the section entitled "The canonical patch format" in the
kernel file, Documentation/process/submitting-patches.rst for what
needs to be done here to properly describe this.
If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.
thanks,
greg k-h's patch email bot
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-08-06 4:41 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-08-05 15:31 [PATCH] usb: serial: ch341: add debugfs interface and clean up Vegom Doster
2026-08-06 4:41 ` Greg KH
[not found] <CACnaG5x_EPK+PGqdrRO-OgOQ3go8EKFdV+R14bKuc9mTS5r31w@mail.gmail.com>
2026-08-05 15:28 ` Vegom Doster
2026-08-06 4:40 ` Greg KH
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