linux-kernel - Re: [PATCH v2 3/5] regcache: flat: Remove unneeded check and error message for -ENOMEM

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Message-ID: <39f251f542baf2148c9e75f94baf0b2188c38e95.camel@svanheule.net>
Date: Thu, 30 Oct 2025 21:18:11 +0100
From: Sander Vanheule <sander@...nheule.net>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Mark Brown
	 <broonie@...nel.org>, Christophe JAILLET <christophe.jaillet@...adoo.fr>, 
	linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki"
	 <rafael@...nel.org>, Danilo Krummrich <dakr@...nel.org>
Subject: Re: [PATCH v2 3/5] regcache: flat: Remove unneeded check and error
 message for -ENOMEM

Hi Andy,

On Thu, 2025-10-30 at 18:37 +0100, Andy Shevchenko wrote:
> There is a convention in the kernel to avoid error messages
> in the cases of -ENOMEM errors. Besides that, the idea behind
> using struct_size() and other macros from overflow.h is
> to saturate the size that the following allocation call will
> definitely fail, hence the check and the error messaging added
> in regcache_flat_init() are redundant. Remove them.
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---

Makes sense, although I couldn't find the failure path myself in the code (it's probably
too deep down in the memory management code). But I see now there are unit tests that
check allocation failure for overflowed sizes.

FWIW

Acked-by: Sander Vanheule <sander@...nheule.net>

Best,
Sander

>  drivers/base/regmap/regcache-flat.c | 10 +---------
>  1 file changed, 1 insertion(+), 9 deletions(-)
> 
> diff --git a/drivers/base/regmap/regcache-flat.c b/drivers/base/regmap/regcache-flat.c
> index 3b9235bb8313..bacb7137092f 100644
> --- a/drivers/base/regmap/regcache-flat.c
> +++ b/drivers/base/regmap/regcache-flat.c
> @@ -30,7 +30,6 @@ struct regcache_flat_data {
>  static int regcache_flat_init(struct regmap *map)
>  {
>  	int i;
> -	size_t cache_data_size;
>  	unsigned int cache_size;
>  	struct regcache_flat_data *cache;
>  
> @@ -38,14 +37,7 @@ static int regcache_flat_init(struct regmap *map)
>  		return -EINVAL;
>  
>  	cache_size = regcache_flat_get_index(map, map->max_register) + 1;
> -	cache_data_size = struct_size(cache, data, cache_size);
> -
> -	if (cache_data_size == SIZE_MAX) {
> -		dev_err(map->dev, "cannot allocate regmap cache");
> -		return -ENOMEM;
> -	}
> -
> -	cache = kzalloc(cache_data_size, map->alloc_flags);
> +	cache = kzalloc(struct_size(cache, data, cache_size), map->alloc_flags);
>  	if (!cache)
>  		return -ENOMEM;
>