Grigori Goronzy <greg@xxxxxxxxxxxx> wrote:
> The status bit was found with USB captures of the Windows
> driver and some luck. Tested on CH340G and CH341A.
By my reversing, bit 0x4, is "multiple status changes since last
interrupt"
>
> Signed-off-by: Grigori Goronzy <greg@xxxxxxxxxxxx>
> ---
> drivers/usb/serial/ch341.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/usb/serial/ch341.c
> b/drivers/usb/serial/ch341.c index 6981e2ad..adf7d79 100644
> --- a/drivers/usb/serial/ch341.c
> +++ b/drivers/usb/serial/ch341.c
> @@ -82,6 +82,8 @@
> #define CH341_LCR_CS6 0x01
> #define CH341_LCR_CS5 0x00
>
> +#define CH341_STATUS_TXBUSY 0x01
> +
> static const struct usb_device_id id_table[] = {
> { USB_DEVICE(0x4348, 0x5523) },
> { USB_DEVICE(0x1a86, 0x7523) },
> @@ -95,6 +97,7 @@ struct ch341_private {
> unsigned baud_rate; /* set baud rate */
> u8 line_control; /* set line control value RTS/DTR */
> u8 line_status; /* active status of modem control inputs */
> + u8 uart_status; /* generic UART status bits */
> };
>
> static void ch341_set_termios(struct tty_struct *tty,
> @@ -187,7 +190,8 @@ static int ch341_get_status(struct usb_device *dev, struct ch341_private *priv)
> if (r == 2) {
> r = 0;
> spin_lock_irqsave(&priv->lock, flags);
> - priv->line_status = (~(*buffer)) & CH341_BITS_MODEM_STAT;
> + priv->line_status = (~buffer[0]) & CH341_BITS_MODEM_STAT;
> + priv->uart_status = buffer[1];
> spin_unlock_irqrestore(&priv->lock, flags);
> } else {
> r = -EPROTO;
> @@ -198,6 +202,18 @@ out:
> return r;
> }
>
> +static bool ch341_tx_empty(struct usb_serial_port *port)
> +{
> + int r;
> + struct ch341_private *priv = usb_get_serial_port_data(port);
> +
> + r = ch341_get_status(port->serial->dev, priv);
> + if (r < 0)
> + return true;
> +
> + return !(priv->uart_status & CH341_STATUS_TXBUSY);
> +}
> +
> /* -------------------------------------------------------------------------- */
>
> static int ch341_configure(struct usb_device *dev, struct ch341_private *priv)
> @@ -606,6 +622,7 @@ static struct usb_serial_driver ch341_device = {
> .carrier_raised = ch341_carrier_raised,
> .close = ch341_close,
> .set_termios = ch341_set_termios,
> + .tx_empty = ch341_tx_empty,
> .break_ctl = ch341_break_ctl,
> .tiocmget = ch341_tiocmget,
> .tiocmset = ch341_tiocmset,
> --
> 1.9.1
>
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