From: Michael Hanselmann <[email protected]> commit c404bf4aa9236cb4d1068e499ae42acf48a6ff97 upstream.
A subset of CH341 devices does not support all features, namely the prescaler is limited to a reduced precision and there is no support for sending a RS232 break condition. This patch adds a detection function which will be extended to set quirk flags as they're implemented. The author's affected device has an imprint of "340" on the turquoise-colored plug, but not all such devices appear to be affected. Signed-off-by: Michael Hanselmann <[email protected]> Link: https://lore.kernel.org/r/1e1ae0da6082bb528a44ef323d4e1d3733d38858.1585697281.git.pub...@hansmi.ch [ johan: use long type for quirks; rephrase and use port device for messages; handle short reads; set quirk flags directly in helper function ] Cc: stable <[email protected]> # 5.5 Signed-off-by: Johan Hovold <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/usb/serial/ch341.c | 53 +++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 53 insertions(+) --- a/drivers/usb/serial/ch341.c +++ b/drivers/usb/serial/ch341.c @@ -87,6 +87,7 @@ struct ch341_private { u8 mcr; u8 msr; u8 lcr; + unsigned long quirks; }; static void ch341_set_termios(struct tty_struct *tty, @@ -308,6 +309,53 @@ out: kfree(buffer); return r; } +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; + char *buffer; + int r; + + buffer = kmalloc(size, GFP_KERNEL); + if (!buffer) + return -ENOMEM; + + /* + * 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(udev, usb_rcvctrlpipe(udev, 0), CH341_REQ_READ_REG, + USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_DIR_IN, + CH341_REG_BREAK, 0, buffer, size, DEFAULT_TIMEOUT); + if (r == -EPIPE) { + dev_dbg(&port->dev, "break control not supported\n"); + r = 0; + goto out; + } + + if (r != size) { + if (r >= 0) + r = -EIO; + dev_err(&port->dev, "failed to read break control: %d\n", r); + goto out; + } + + r = 0; +out: + kfree(buffer); + + 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; @@ -330,6 +378,11 @@ static int ch341_port_probe(struct usb_s goto error; usb_set_serial_port_data(port, priv); + + r = ch341_detect_quirks(port); + if (r < 0) + goto error; + return 0; error: kfree(priv);
