linux-kernel - Re: [PATCH] tty: gdm724x: use min_t() for size

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Date:   Wed, 16 Aug 2023 10:13:38 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Cc:     gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] tty: gdm724x: use min_t() for size_t varable and a
 constant

On Wed, Aug 16, 2023 at 10:53:22AM +0200, Jiri Slaby (SUSE) wrote:
> My thinking was that ulong is the same as size_t everywhere. No, size_t
> is uint on 32bit. So the below commit introduced a build warning on
> 32bit:
> .../gdm724x/gdm_tty.c:165:24: warning: comparison of distinct pointer types ('typeof (2048UL) *' (aka 'unsigned long *') and 'typeof (remain) *' (aka 'unsigned int *'))
> 
> To fix this, partially revert the commit (remove constants' suffixes)
> and switch to min_t() in this case instead.
> 
> /me would hope for Z (or alike) suffix for constants.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> Fixes: c3e5c706aefc (tty: gdm724x: convert counts to size_t)
> Reported-by: Nathan Chancellor <nathan@...nel.org>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202308151953.rNNnAR2N-lkp@intel.com/

Tested-by: Nathan Chancellor <nathan@...nel.org> # build

> ---
>  drivers/staging/gdm724x/gdm_tty.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/gdm724x/gdm_tty.c b/drivers/staging/gdm724x/gdm_tty.c
> index 67d9bf41e836..32b2e817ff04 100644
> --- a/drivers/staging/gdm724x/gdm_tty.c
> +++ b/drivers/staging/gdm724x/gdm_tty.c
> @@ -17,9 +17,9 @@
>  #define GDM_TTY_MAJOR 0
>  #define GDM_TTY_MINOR 32
>  
> -#define WRITE_SIZE 2048UL
> +#define WRITE_SIZE 2048
>  
> -#define MUX_TX_MAX_SIZE 2048UL
> +#define MUX_TX_MAX_SIZE 2048
>  
>  static inline bool gdm_tty_ready(struct gdm *gdm)
>  {
> @@ -159,7 +159,7 @@ static ssize_t gdm_tty_write(struct tty_struct *tty, const u8 *buf, size_t len)
>  		return -ENODEV;
>  
>  	while (remain) {
> -		size_t sending_len = min(MUX_TX_MAX_SIZE, remain);
> +		size_t sending_len = min_t(size_t, MUX_TX_MAX_SIZE, remain);
>  		gdm->tty_dev->send_func(gdm->tty_dev->priv_dev,
>  					(void *)(buf + sent_len),
>  					sending_len,
> -- 
> 2.41.0
>