From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
This is not allowed by the spec and does in fact not make any sense.
Return -EINVAL if this is the case.
Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
---
drivers/media/v4l2-core/videobuf2-core.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index b7de6be..c662ad9 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1511,6 +1511,19 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
dprintk(1, "plane parameters verification failed: %d\n", ret);
return ret;
}
+ if (b->field == V4L2_FIELD_ALTERNATE && V4L2_TYPE_IS_OUTPUT(q->type)) {
+ /*
+ * If the format's field is ALTERNATE, then the buffer's field
+ * should be either TOP or BOTTOM, not ALTERNATE since that
+ * makes no sense. The driver has to know whether the
+ * buffer represents a top or a bottom field in order to
+ * program any DMA correctly. Using ALTERNATE is wrong, since
+ * that just says that it is either a top or a bottom field,
+ * but not which of the two it is.
+ */
+ dprintk(1, "the field is incorrectly set to ALTERNATE for an output buffer\n");
+ return -EINVAL;
+ }
vb->state = VB2_BUF_STATE_PREPARING;
vb->v4l2_buf.timestamp.tv_sec = 0;
--
1.9.1
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