On Mon, Jan 18, 2021 at 12:13:26PM +0100, Johan Hovold wrote: > From: Wang Sheng Long <shenglong.wang.ext@xxxxxxxxxxx> > > When data is transmitted between two serial ports, the phenomenon of > data loss often occurs. The two kinds of flow control commonly used in > serial communication are hardware flow control and software flow > control. > > In serial communication, If you only use RX/TX/GND Pins, you can't do > hardware flow. So we often used software flow control and prevent data > loss. The user sets the software flow control through the application > program, and the application program sets the software flow control mode > for the serial port chip through the driver. > > For the cp210 serial port chip, its driver lacks the software flow > control setting code, so the user cannot set the software flow control > function through the application program. This adds the missing software > flow control. > > Signed-off-by: Wang Sheng Long <shenglong.wang.ext@xxxxxxxxxxx> > Link: https://lore.kernel.org/r/20210104094502.3942-1-china_shenglong@xxxxxxx > [ johan: rework properly on top of recent termios changes ] > Signed-off-by: Johan Hovold <johan@xxxxxxxxxx> > --- > drivers/usb/serial/cp210x.c | 67 +++++++++++++++++++++++++++++++++++-- > 1 file changed, 65 insertions(+), 2 deletions(-) > > diff --git a/drivers/usb/serial/cp210x.c b/drivers/usb/serial/cp210x.c > index fbb10dfc56e3..5bd14770065b 100644 > --- a/drivers/usb/serial/cp210x.c > +++ b/drivers/usb/serial/cp210x.c > @@ -377,6 +377,16 @@ static struct usb_serial_driver * const serial_drivers[] = { > #define CONTROL_WRITE_DTR 0x0100 > #define CONTROL_WRITE_RTS 0x0200 > > +/* CP210X_(GET|SET)_CHARS */ > +struct cp210x_special_chars { > + u8 bEofChar; > + u8 bErrorChar; > + u8 bBreakChar; > + u8 bEventChar; > + u8 bXonChar; > + u8 bXoffChar; > +}; > + > /* CP210X_VENDOR_SPECIFIC values */ > #define CP210X_READ_2NCONFIG 0x000E > #define CP210X_READ_LATCH 0x00C2 > @@ -1074,11 +1084,38 @@ static void cp210x_disable_event_mode(struct usb_serial_port *port) > port_priv->event_mode = false; > } > > +static int cp210x_set_chars(struct usb_serial_port *port, > + struct cp210x_special_chars *chars) > +{ > + struct cp210x_port_private *port_priv = usb_get_serial_port_data(port); > + struct usb_serial *serial = port->serial; > + void *dmabuf; > + int result; > + > + dmabuf = kmemdup(chars, sizeof(*chars), GFP_KERNEL); > + if (!dmabuf) > + return -ENOMEM; > + > + result = usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0), > + CP210X_SET_CHARS, REQTYPE_HOST_TO_INTERFACE, 0, > + port_priv->bInterfaceNumber, > + dmabuf, sizeof(*chars), USB_CTRL_SET_TIMEOUT); > + > + kfree(dmabuf); > + > + if (result < 0) { > + dev_err(&port->dev, "failed to set special chars: %d\n", result); > + return result; > + } This is an "open coded" usb_control_msg_send() call :) Other than that minor thing: Reviewed-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
