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 5a5fb7f..2adc4a9 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -2255,6 +2255,7 @@ 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;
unsigned int q_count;
unsigned int dq_count;
@@ -2356,6 +2357,7 @@ 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;
}
/*
@@ -2434,7 +2436,7 @@ 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.
@@ -2448,7 +2450,7 @@ 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];
/*
@@ -2526,6 +2528,7 @@ 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;
}
/*
--
1.8.5.2
--
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