Re: [PATCH V2 2/7] USB: serial: f81232: Add tx_empty function

[Johan Hovold <johan@kernel.org>]

On Mon, Sep 23, 2019 at 10:24:44AM +0800, Ji-Ze Hong (Peter Hong) wrote:
> Add tx_empty() function for F81232.
> 
> Signed-off-by: Ji-Ze Hong (Peter Hong) <hpeter+linux_kernel@gmail.com>
> ---
>  drivers/usb/serial/f81232.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/drivers/usb/serial/f81232.c b/drivers/usb/serial/f81232.c
> index c07d376c743d..b42b3738a768 100644
> --- a/drivers/usb/serial/f81232.c
> +++ b/drivers/usb/serial/f81232.c
> @@ -685,6 +685,23 @@ 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;
> +
> +	status = f81232_get_register(port, LINE_STATUS_REGISTER, &tmp);
> +	if (status) {
> +		dev_err(&port->dev, "get LSR status failed: %d\n", status);
> +		return false;

You need to return true here on errors like the other drivers do
(consider a disconnected device where you end up with -ENODEV here).

> +	}
> +
> +	if ((tmp & UART_LSR_TEMT) != UART_LSR_TEMT)
> +		return false;
> +
> +	return true;
> +}

Johan