Hi Brandon,
On Sat, Jun 22, 2024 at 07:57:43AM +0100, Brandon Cheo Fusi wrote:
> When dealing with a userptr pointing to a buffer in userspace,
> videobuf2 swaps the corresponding physical pages with other pages
> so we have a contiguous area of memory for DMA. This only works if
> the userptr is page aligned.
>
> The current way of allocating user buffers using malloc only
> guarantees alignment up to `alignof(max_align_t)`, which is usually
> 16. So replace malloc with posix_memalign to ensure the returned
> pointer is on a page boundary.
>
> Signed-off-by: Brandon Cheo Fusi <fusibrandon13@xxxxxxxxx>
> ---
> utils/common/v4l-helpers.h | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/utils/common/v4l-helpers.h b/utils/common/v4l-helpers.h
> index cf0e92d..4104b53 100644
> --- a/utils/common/v4l-helpers.h
> +++ b/utils/common/v4l-helpers.h
> @@ -1656,15 +1656,16 @@ static inline int v4l_queue_alloc_bufs(struct v4l_fd *f,
> struct v4l_queue *q, unsigned from)
> {
> unsigned b, p;
> + void *m;
> + int ret;
>
> if (q->memory != V4L2_MEMORY_USERPTR)
> return 0;
> for (b = from; b < v4l_queue_g_buffers(q); b++) {
> for (p = 0; p < v4l_queue_g_num_planes(q); p++) {
> - void *m = malloc(v4l_queue_g_length(q, p));
Please continue declaring m and ret here. They're not used outside the loop
(and should not be).
> -
> - if (m == NULL)
> - return errno;
> + ret = posix_memalign(&m, getpagesize(), v4l_queue_g_length(q, p));
Over 80 characters per line for no apparent reason.
> + if (ret)
> + return ret;
> v4l_queue_s_userptr(q, b, p, m);
> }
> }
--
Kind regards,
Sakari Ailus
