linux-kernel - Re: [PATCH] drivers: applicom: remove set but not used variable 'byte_reset

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Date:   Tue, 21 Jul 2020 10:54:41 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Zheng Yongjun <zhengyongjun3@...wei.com>
Cc:     arnd@...db.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: applicom: remove set but not used variable
 'byte_reset_it'

On Tue, Jul 21, 2020 at 04:41:07PM +0800, Zheng Yongjun wrote:
> Fixes gcc '-Wunused-but-set-variable' warning:
> 
> drivers/char/applicom.c: In function 'ac_register_board':
> drivers/char/applicom.c:543: warning:
> variable 'byte_reset_it' set but not used [-Wunused-but-set-variable]
> 
> Signed-off-by: Zheng Yongjun <zhengyongjun3@...wei.com>
> ---
>  drivers/char/applicom.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/drivers/char/applicom.c b/drivers/char/applicom.c
> index 14b2d8034c51..fd0b21607a7f 100644
> --- a/drivers/char/applicom.c
> +++ b/drivers/char/applicom.c
> @@ -131,8 +131,6 @@ static int dummy;	/* dev_id for request_irq() */
>  static int ac_register_board(unsigned long physloc, void __iomem *loc, 
>  		      unsigned char boardno)
>  {
> -	volatile unsigned char byte_reset_it;
> -
>  	if((readb(loc + CONF_END_TEST)     != 0x00) ||
>  	   (readb(loc + CONF_END_TEST + 1) != 0x55) ||
>  	   (readb(loc + CONF_END_TEST + 2) != 0xAA) ||
> @@ -160,7 +158,6 @@ static int ac_register_board(unsigned long physloc, void __iomem *loc,
>  	apbs[boardno].RamIO = loc;
>  	init_waitqueue_head(&apbs[boardno].FlagSleepSend);
>  	spin_lock_init(&apbs[boardno].mutex);
> -	byte_reset_it = readb(loc + RAM_IT_TO_PC);

Are you sure you didn't just break the driver?  Lots of times reading
from hardware is required in order to have previous things work, or even
have other affects.

thanks,

greg k-h