Re: [PATCH v2] media: staging: ipu3: img-mmu: fix sign-to-unsigned conversion

[Dan Carpenter <dan.carpenter@linaro.org>]

On Fri, Mar 06, 2026 at 10:43:20PM +0800, Richard Lyu wrote:
> imgu_mmu_unmap() returns size_t (unsigned), representing the number of
> bytes successfully unmapped. However, when the alignment check fails,
> it currently returns -EINVAL.
> 
> On 64-bit systems, this negative error code is implicitly converted
> to a very large unsigned value (18446744073709551594). The same happens
> on 32-bit systems as well, although the resulting value is smaller.
> 
> Return 0 when the alignment check fails to correctly indicate that
> no bytes were unmapped while resolving the following
> -Wsign-conversion warning:
> 
> drivers/staging/media/ipu3/ipu3-mmu.c:393:24: warning: unsigned
> conversion from 'int' to 'size_t' {aka 'long unsigned int'} changes
> value from '-22' to '18446744073709551594' [-Wsign-conversion]
>   393 |         return -EINVAL;
> 
> All callers ignore the return value, so this change does not affect
> existing behavior.
> 
> Fixes: 26f5689592e2 ("media: staging/intel-ipu3: mmu: Implement driver")
> Signed-off-by: Richard Lyu <richard.lyu@suse.com>
> ---
> v2:
> - Added note that this affects 32-bit systems as well.
> - Clarified that all callers ignore the return value.
> - Added Fixes tag.
> - Link: https://lore.kernel.org/all/aarQeHfQuq20gXH0@stanley.mountain/

Thanks!

Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>

regards,
dan carpenter