[PATCH for v4.20] vb2: skip request checks for VIDIOC_PREPARE_BUF

[Hans Verkuil]

VIDIOC_PREPARE_BUF should ignore V4L2_BUF_FLAG_REQUEST_FD since it isn't
doing anything with requests. So inform vb2_queue_or_prepare_buf whether
it is called from vb2_prepare_buf or vb2_qbuf and just return 0 in the
first case.

This was found when adding new v4l2-compliance checks.

Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
---
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c 
b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 1244c246d0c4..1ac1b3f334f6 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -332,10 +332,10 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer 
*vb, struct v4l2_buffer *b
 }

 static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct media_device 
*mdev,
-                                   struct v4l2_buffer *b,
-                                   const char *opname,
+                                   struct v4l2_buffer *b, bool is_prepare,
                                    struct media_request **p_req)
 {
+       const char *opname = is_prepare ? "prepare_buf" : "qbuf";
        struct media_request *req;
        struct vb2_v4l2_buffer *vbuf;
        struct vb2_buffer *vb;
@@ -377,6 +377,9 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, 
struct media_device *md
                        return ret;
        }

+       if (is_prepare)
+               return 0;
+
        if (!(b->flags & V4L2_BUF_FLAG_REQUEST_FD)) {
                if (q->uses_requests) {
                        dprintk(1, "%s: queue uses requests\n", opname);
@@ -656,7 +659,7 @@ int vb2_prepare_buf(struct vb2_queue *q, struct 
media_device *mdev,
        if (b->flags & V4L2_BUF_FLAG_REQUEST_FD)
                return -EINVAL;

-       ret = vb2_queue_or_prepare_buf(q, mdev, b, "prepare_buf", NULL);
+       ret = vb2_queue_or_prepare_buf(q, mdev, b, true, NULL);

        return ret ? ret : vb2_core_prepare_buf(q, b->index, b);
 }
@@ -728,7 +731,7 @@ int vb2_qbuf(struct vb2_queue *q, struct media_device *mdev,
                return -EBUSY;
        }

-       ret = vb2_queue_or_prepare_buf(q, mdev, b, "qbuf", &req);
+       ret = vb2_queue_or_prepare_buf(q, mdev, b, false, &req);
        if (ret)
                return ret;
        ret = vb2_core_qbuf(q, b->index, b, req);