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

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

On Fri, Mar 06, 2026 at 06:43:59PM +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),

That happens on a 32bit also, although of course, the number would be
smaller.

> incorrectly
> indicating that memory was unmapped and potentially breaking the
> caller's logic.
> 

All the callers ignore the return value so it doesn't actually affect
anything.  The commit message needs to say this.

> 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;
> 
> Signed-off-by: Richard Lyu <richard.lyu@suse.com>

Please add a Fixes tag.

Otherwise, the fix looks okay to me.

regards,
dan carpenter