linux-kernel - Re: [PATCH 34/36] tty: gdm724x: convert counts to size

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Date:   Tue, 15 Aug 2023 10:22:47 -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, linux-staging@...ts.linux.dev
Subject: Re: [PATCH 34/36] tty: gdm724x: convert counts to size_t

On Thu, Aug 10, 2023 at 11:15:08AM +0200, Jiri Slaby (SUSE) wrote:
> Unify the type of tty_operations::write() counters with the 'count'
> parameter. I.e. use size_t for them.
> 
> This includes changing constants to UL to keep min() and avoid min_t().

This patch appears to cause a warning/error on 32-bit architectures now
due to this part of the change, as size_t is 'unsigned int' there:

  In file included from include/linux/kernel.h:27,
                   from drivers/staging/gdm724x/gdm_tty.c:6:
  drivers/staging/gdm724x/gdm_tty.c: In function 'gdm_tty_write':
  include/linux/minmax.h:21:35: error: comparison of distinct pointer types lacks a cast [-Werror]
     21 |         (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
        |                                   ^~
  include/linux/minmax.h:27:18: note: in expansion of macro '__typecheck'
     27 |                 (__typecheck(x, y) && __no_side_effects(x, y))
        |                  ^~~~~~~~~~~
  include/linux/minmax.h:37:31: note: in expansion of macro '__safe_cmp'
     37 |         __builtin_choose_expr(__safe_cmp(x, y), \
        |                               ^~~~~~~~~~
  include/linux/minmax.h:68:25: note: in expansion of macro '__careful_cmp'
     68 | #define min(x, y)       __careful_cmp(x, y, <)
        |                         ^~~~~~~~~~~~~
  drivers/staging/gdm724x/gdm_tty.c:162:38: note: in expansion of macro 'min'
    162 |                 size_t sending_len = min(MUX_TX_MAX_SIZE, remain);
        |                                      ^~~
  cc1: all warnings being treated as errors

> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> Cc: linux-staging@...ts.linux.dev
> ---
>  drivers/staging/gdm724x/gdm_tty.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/staging/gdm724x/gdm_tty.c b/drivers/staging/gdm724x/gdm_tty.c
> index b31f2afb0286..cbaaa8fa7474 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 2048
> +#define WRITE_SIZE 2048UL
>  
> -#define MUX_TX_MAX_SIZE 2048
> +#define MUX_TX_MAX_SIZE 2048UL
>  
>  static inline bool gdm_tty_ready(struct gdm *gdm)
>  {
> @@ -152,9 +152,8 @@ static void gdm_tty_send_complete(void *arg)
>  static ssize_t gdm_tty_write(struct tty_struct *tty, const u8 *buf, size_t len)
>  {
>  	struct gdm *gdm = tty->driver_data;
> -	int remain = len;
> -	int sent_len = 0;
> -	int sending_len = 0;
> +	size_t remain = len;
> +	size_t sent_len = 0;
>  
>  	if (!gdm_tty_ready(gdm))
>  		return -ENODEV;
> @@ -163,7 +162,7 @@ static ssize_t gdm_tty_write(struct tty_struct *tty, const u8 *buf, size_t len)
>  		return 0;
>  
>  	while (1) {
> -		sending_len = min(MUX_TX_MAX_SIZE, remain);
> +		size_t sending_len = min(MUX_TX_MAX_SIZE, remain);
>  		gdm->tty_dev->send_func(gdm->tty_dev->priv_dev,
>  					(void *)(buf + sent_len),
>  					sending_len,
> -- 
> 2.41.0
>