linux-kernel - Re: [PATCH v2] tty: serial: samsung: remove variable 'ufstat' set but not used

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Date:   Fri, 22 Nov 2019 13:08:37 +0100
From:   Jiri Slaby <jslaby@...e.com>
To:     Chen Wandun <chenwandun@...wei.com>, gregkh@...uxfoundation.org,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        beomho.seo@...sung.com, sw0312.kim@...sung.com,
        youngmin.nam@...sung.com
Subject: Re: [PATCH v2] tty: serial: samsung: remove variable 'ufstat' set but
 not used

On 22. 11. 19, 13:04, Chen Wandun wrote:
> Fixes gcc '-Wunused-but-set-variable' warning:
> 
> drivers/tty/serial/samsung_tty.c: In function s3c24xx_serial_rx_chars_dma:
> drivers/tty/serial/samsung_tty.c:549:24: warning: variable ufstat set but not used [-Wunused-but-set-variable]
> 
> Signed-off-by: Chen Wandun <chenwandun@...wei.com>
> ---
>  drivers/tty/serial/samsung_tty.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index 83fd516..ab3c7d1 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -546,7 +546,7 @@ static void s3c24xx_serial_rx_drain_fifo(struct s3c24xx_uart_port *ourport);
>  
>  static irqreturn_t s3c24xx_serial_rx_chars_dma(void *dev_id)
>  {
> -	unsigned int utrstat, ufstat, received;
> +	unsigned int utrstat, received;
>  	struct s3c24xx_uart_port *ourport = dev_id;
>  	struct uart_port *port = &ourport->port;
>  	struct s3c24xx_uart_dma *dma = ourport->dma;
> @@ -556,7 +556,7 @@ static irqreturn_t s3c24xx_serial_rx_chars_dma(void *dev_id)
>  	struct dma_tx_state state;
>  
>  	utrstat = rd_regl(port, S3C2410_UTRSTAT);
> -	ufstat = rd_regl(port, S3C2410_UFSTAT);
> +	rd_regl(port, S3C2410_UFSTAT);

The question (CCed some samsung people) is whether we have to spend the
cycles reading the register at all? Does it have side-effects?

thanks,
-- 
js
suse labs