On (21/07/26 13:22), Tomasz Figa wrote:

quoted

quoted

I guess ->flags can become u8 for both create-bufs and req-bufs.
We had ->flags in both structs as u32, but then decided to leave
some reserved[] space in req-bufs and switched to u8 there.

diff --git a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
index a048a9f6b7b6..cf633b5a4919 100644
--- a/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst
+++ b/Documentation/userspace-api/media/v4l/vidioc-create-bufs.rst

@@ -112,13 +112,13 @@ than the number requested.
        other changes, then set ``count`` to 0, ``memory`` to
        ``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.

-    * - __u32
+    * - __u8
       - ``flags``
       - Specifies additional buffer management attributes.
        See :ref:`memory-flags`.

-    * - __u32
-      - ``reserved``\ [6]
+    * - __u8
+      - ``reserved``\ [27]
       - A place holder for future extensions. Drivers and applications
        must set the array to zero.

diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 6edf4508c636..2ae949ec0afa 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c

@@ -694,7 +694,7 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)

 static void validate_memory_flags(struct vb2_queue *q,
                                  int memory,
-                                 u32 *flags)
+                                 u8 *flags)
 {
        if (!q->allow_cache_hints || memory != V4L2_MEMORY_MMAP) {
                /*

@@ -711,11 +711,9 @@ static void validate_memory_flags(struct vb2_queue *q,
 int vb2_reqbufs(struct vb2_queue *q, struct v4l2_requestbuffers *req)
 {
        int ret = vb2_verify_memory_type(q, req->memory, req->type);
-       u32 flags = req->flags;

        fill_buf_caps(q, &req->capabilities);
-       validate_memory_flags(q, req->memory, &flags);
-       req->flags = flags;
+       validate_memory_flags(q, req->memory, &req->flags);
        return ret ? ret : vb2_core_reqbufs(q, req->memory,
                                            req->flags, &req->count);
 }

@@ -990,11 +988,9 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
 {
        struct video_device *vdev = video_devdata(file);
        int res = vb2_verify_memory_type(vdev->queue, p->memory, p->type);
-       u32 flags = p->flags;

        fill_buf_caps(vdev->queue, &p->capabilities);
-       validate_memory_flags(vdev->queue, p->memory, &flags);
-       p->flags = flags;
+       validate_memory_flags(vdev->queue, p->memory, &p->flags);
        if (res)
                return res;
        if (vb2_queue_is_busy(vdev, file))

diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 7973aa0465d2..ad4f7cee53f2 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h

@@ -2513,8 +2513,8 @@ struct v4l2_create_buffers {
        __u32                   memory;
        struct v4l2_format      format;
        __u32                   capabilities;
-       __u32                   flags;
-       __u32                   reserved[6];
+       __u8                    flags;
+       __u8                    reserved[27];
 };

 /*

I don't think we want this UABI churn anymore for a trivial
simplification in the implementation.

OK, I can scratch it. I thought that for API symmetry we can have
::memory-flags of the same type/size in create-bufs and req-bufs,
but don't have any strong opinion on this.