On Thu, Feb 13, 2014 at 6:40 PM, Hans Verkuil <hverkuil@xxxxxxxxx> wrote:
> From: Hans Verkuil <hans.verkuil@xxxxxxxxx>
>
> Commit 88e268702bfba78448abd20a31129458707383aa ("vb2: Improve file I/O
> emulation to handle buffers in any order") broke read/write support if
> the size of the buffer being read/written is less than the size of the
> image.
>
> When the commit was tested originally I used qv4l2, which call read()
> with exactly the size of the image. But if you try 'cat /dev/video0'
> then it will fail and typically hang after reading two buffers.
>
> This patch fixes the behavior by adding a new buf_index field that
> contains the index of the field currently being filled/read, or it
> is num_buffers in which case a new buffer needs to be dequeued.
>
> Signed-off-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
> Cc: Andy Walls <awalls@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/v4l2-core/videobuf2-core.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> index 7766bf5..a3b4b4c 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -2418,6 +2418,7 @@ struct vb2_fileio_data {
> struct v4l2_requestbuffers req;
> struct v4l2_buffer b;
> struct vb2_fileio_buf bufs[VIDEO_MAX_FRAME];
> + unsigned int buf_index;
> unsigned int index;
The two index fields are now confusing, especially because there is no
documentation. Perhaps we could call index "cur_index" and also add
documentation please?
> unsigned int q_count;
> unsigned int dq_count;
> @@ -2519,6 +2520,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
> fileio->bufs[i].queued = 1;
> }
> fileio->index = q->num_buffers;
> + fileio->buf_index = q->num_buffers;
> }
>
> /*
> @@ -2597,7 +2599,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
> /*
> * Check if we need to dequeue the buffer.
> */
> - index = fileio->index;
> + index = fileio->buf_index;
> if (index >= q->num_buffers) {
> /*
> * Call vb2_dqbuf to get buffer back.
> @@ -2611,7 +2613,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
> return ret;
> fileio->dq_count += 1;
>
> - index = fileio->b.index;
> + fileio->buf_index = index = fileio->b.index;
> buf = &fileio->bufs[index];
>
> /*
> @@ -2689,6 +2691,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
> fileio->q_count += 1;
> if (fileio->index < q->num_buffers)
> fileio->index++;
> + fileio->buf_index = fileio->index;
> }
>
> /*
> --
> 1.8.4.rc3
>
--
Best regards,
Pawel Osciak
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