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));
-
- if (m == NULL)
- return errno;
+ ret = posix_memalign(&m, getpagesize(), v4l_queue_g_length(q, p));
+ if (ret)
+ return ret;
v4l_queue_s_userptr(q, b, p, m);
}
}
--
2.39.2
