linux-kernel - Re: [PATCH] serial: Fix an invalid comparing statement

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Date:   Mon, 10 Jun 2019 18:56:55 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Sugaya Taichi <sugaya.taichi@...ionext.com>
Cc:     Jiri Slaby <jslaby@...e.com>,
        Takao Orito <orito.takao@...ionext.com>,
        Kazuhiro Kasai <kasai.kazuhiro@...ionext.com>,
        Shinji Kanematsu <kanematsu.shinji@...ionext.com>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        Masami Hiramatsu <masami.hiramatsu@...aro.org>,
        linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org
Subject: Re: [PATCH] serial: Fix an invalid comparing statement

On Mon, May 27, 2019 at 02:01:27PM +0900, Sugaya Taichi wrote:
> Drop the if-statement which refers to 8th bit field of u8 variable.
> The bit field is no longer used.
> 
> Fixes: ba44dc043004 ("serial: Add Milbeaut serial control")
> Reported-by: Colin Ian King <colin.king@...onical.com>
> Signed-off-by: Sugaya Taichi <sugaya.taichi@...ionext.com>
> ---
>  drivers/tty/serial/milbeaut_usio.c | 15 +++++----------
>  1 file changed, 5 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/tty/serial/milbeaut_usio.c b/drivers/tty/serial/milbeaut_usio.c
> index 949ab7e..d7207ab 100644
> --- a/drivers/tty/serial/milbeaut_usio.c
> +++ b/drivers/tty/serial/milbeaut_usio.c
> @@ -56,7 +56,6 @@
>  #define MLB_USIO_SSR_FRE		BIT(4)
>  #define MLB_USIO_SSR_PE			BIT(5)
>  #define MLB_USIO_SSR_REC		BIT(7)
> -#define MLB_USIO_SSR_BRK		BIT(8)
>  #define MLB_USIO_FCR_FE1		BIT(0)
>  #define MLB_USIO_FCR_FE2		BIT(1)
>  #define MLB_USIO_FCR_FCL1		BIT(2)
> @@ -180,18 +179,14 @@ static void mlb_usio_rx_chars(struct uart_port *port)
>  		if (status & MLB_USIO_SSR_ORE)
>  			port->icount.overrun++;
>  		status &= port->read_status_mask;
> -		if (status & MLB_USIO_SSR_BRK) {
> -			flag = TTY_BREAK;
> +		if (status & MLB_USIO_SSR_PE) {
> +			flag = TTY_PARITY;
>  			ch = 0;
>  		} else
> -			if (status & MLB_USIO_SSR_PE) {
> -				flag = TTY_PARITY;
> +			if (status & MLB_USIO_SSR_FRE) {
> +				flag = TTY_FRAME;
>  				ch = 0;
> -			} else
> -				if (status & MLB_USIO_SSR_FRE) {
> -					flag = TTY_FRAME;
> -					ch = 0;
> -				}
> +			}
>  		if (flag)
>  			uart_insert_char(port, status, MLB_USIO_SSR_ORE,
>  					 ch, flag);

While the code never actually supported Break, you are explicitly
removing that logic now.  So shouldn't you instead _fix_ break handling?
The code before and after your change does not work any differently, so
this patch isn't really needed at this point.

thanks,

greg k-h