Re: [PATCH 34/36] tty: serial: pmac_zilog: Make disposable variable __always_unused

[Christophe Leroy]

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@xxxxxxxxxxxxxxxxxxx>
> Cc: Jiri Slaby <jirislaby@xxxxxxxxxx>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: linux-serial@xxxxxxxxxxxxxxx
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
> ---
>   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); \