linux-kernel - Re: [PATCH 17/17] tty: srmcons: make 'str

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Message-ID: <885063ee-b0da-42cc-b836-da2117d4d3aa@linaro.org>
Date:   Tue, 21 Nov 2023 11:58:27 -0600
From:   Richard Henderson <richard.henderson@...aro.org>
To:     "Jiri Slaby (SUSE)" <jirislaby@...nel.org>,
        gregkh@...uxfoundation.org
Cc:     linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>, linux-alpha@...r.kernel.org
Subject: Re: [PATCH 17/17] tty: srmcons: make 'str_cr' const and non-array

On 11/21/23 03:22, Jiri Slaby (SUSE) wrote:
> 'str_cr' contains a single character: \n. There is no need to declare it
> as array. Declare it as a variable, make it const and pass a pointer to
> it to callback_puts().
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> Cc: Richard Henderson <richard.henderson@...aro.org>
> Cc: Ivan Kokshaysky <ink@...assic.park.msu.ru>
> Cc: Matt Turner <mattst88@...il.com>
> Cc: linux-alpha@...r.kernel.org
> ---
>   arch/alpha/kernel/srmcons.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/alpha/kernel/srmcons.c b/arch/alpha/kernel/srmcons.c
> index c6b821afbfd3..a6cff61706b5 100644
> --- a/arch/alpha/kernel/srmcons.c
> +++ b/arch/alpha/kernel/srmcons.c
> @@ -91,7 +91,7 @@ srmcons_receive_chars(struct timer_list *t)
>   static void
>   srmcons_do_write(struct tty_port *port, const char *buf, int count)
>   {
> -	static char str_cr[1] = "\r";
> +	static const char str_cr = '\r';

Best to remove this entirely...

>   	size_t c;
>   	srmcons_result result;
>   
> @@ -119,7 +119,7 @@ srmcons_do_write(struct tty_port *port, const char *buf, int count)
>   		}
>   
>   		while (need_cr) {
> -			result.as_long = callback_puts(0, str_cr, 1);
> +			result.as_long = callback_puts(0, &str_cr, 1);

... and simply use "\r" here.

Logically it adds one '\0' of const data, but it is virtually certain that even more bytes 
of padding are present anyway.  As a string literal it will be placed into .rodata.str1.1 
and packed with other strings.


r~