Re: [PATCH V1 4/6] USB: serial: f81232: Add tx_empty function

[Johan Hovold <johan@kernel.org>]

On Thu, Jun 06, 2019 at 10:54:14AM +0800, Ji-Ze Hong (Peter Hong) wrote:
> Add tx_empty() function for F81232 & F81534A series.
> 
> Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
> ---
>  drivers/usb/serial/f81232.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
> index e9470fb0d691..7d1ec8f9d168 100644
> --- a/drivers/usb/serial/f81232.c
> +++ b/drivers/usb/serial/f81232.c
> @@ -850,6 +850,24 @@ static void f81232_dtr_rts(struct usb_serial_port *port, int on)
>  		f81232_set_mctrl(port, 0, TIOCM_DTR | TIOCM_RTS);
>  }
>  
> +static bool f81232_tx_empty(struct usb_serial_port *port)
> +{
> +	int status;
> +	u8 tmp;
> +	u8 both_empty = UART_LSR_TEMT | UART_LSR_THRE;

Doesn't TEMT being set imply that THRE is set? So you only need to check
the former?

> +
> +	status = f81232_get_register(port, LINE_STATUS_REGISTER, &tmp);
> +	if (status) {
> +		dev_err(&port->dev, "get LSR status failed: %d\n", status);
> +		return false;
> +	}
> +
> +	if ((tmp & both_empty) != both_empty)
> +		return false;
> +
> +	return true;
> +}
> +
>  static int f81232_carrier_raised(struct usb_serial_port *port)
>  {
>  	u8 msr;
> @@ -1279,6 +1297,7 @@ static struct usb_serial_driver f81232_device = {
>  	.tiocmget =		f81232_tiocmget,
>  	.tiocmset =		f81232_tiocmset,
>  	.tiocmiwait =		usb_serial_generic_tiocmiwait,
> +	.tx_empty =		f81232_tx_empty,
>  	.process_read_urb =	f81232_read_urb_proxy,
>  	.read_int_callback =	f81232_read_int_callback,
>  	.port_probe =		f81232_port_probe,

Johan