linux-kernel - Re: [PATCH 34/36] tty: serial: pmac_zilog: Make disposable variable __always

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Message-ID: <445a6440-b4c8-4536-891b-0cefc78e5f57@csgroup.eu>
Date:   Thu, 5 Nov 2020 08:04:44 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        Paul Mackerras <paulus@...ba.org>,
        linux-serial@...r.kernel.org, Jiri Slaby <jirislaby@...nel.org>
Subject: Re: [PATCH 34/36] tty: serial: pmac_zilog: Make disposable variable
 __always_unused



Le 04/11/2020 à 20:35, Lee Jones a écrit :
> Fixes the following W=1 kernel build warning(s):
> 
>   drivers/tty/serial/pmac_zilog.h:365:58: warning: variable ‘garbage’ set but not used [-Wunused-but-set-variable]

Explain how you are fixing this warning.

Setting  __always_unused is usually not the good solution for fixing this warning, but here I guess 
this is likely the good solution. But it should be explained why.

Christophe


> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Jiri Slaby <jirislaby@...nel.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: linux-serial@...r.kernel.org
> Cc: linuxppc-dev@...ts.ozlabs.org
> Signed-off-by: Lee Jones <lee.jones@...aro.org>
> ---
>   drivers/tty/serial/pmac_zilog.h | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/pmac_zilog.h b/drivers/tty/serial/pmac_zilog.h
> index bb874e76810e0..968aec7c1cf82 100644
> --- a/drivers/tty/serial/pmac_zilog.h
> +++ b/drivers/tty/serial/pmac_zilog.h
> @@ -362,7 +362,7 @@ static inline void zssync(struct uart_pmac_port *port)
>   
>   /* Misc macros */
>   #define ZS_CLEARERR(port)    (write_zsreg(port, 0, ERR_RES))
> -#define ZS_CLEARFIFO(port)   do { volatile unsigned char garbage; \
> +#define ZS_CLEARFIFO(port)   do { volatile unsigned char __always_unused garbage; \
>   				     garbage = read_zsdata(port); \
>   				     garbage = read_zsdata(port); \
>   				     garbage = read_zsdata(port); \
>