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[media] vb2: fix read/write regression

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Commit 88e268702b ("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 calls 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 cur_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.

The old index field has been renamed to initial_index in order to be
a bit more descriptive.

This has been tested with both read and write.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Hans Verkuil <hans.verkuil@cisco.com>
Cc: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>
This commit is contained in:
Hans Verkuil 2014-02-14 06:46:50 -03:00 committed by Mauro Carvalho Chehab
parent 249f5a58bc
commit 4e5a4d8a8e
1 changed files with 40 additions and 6 deletions
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46
drivers/media/v4l2-core/videobuf2-core.c
View file

@ -2310,6 +2310,22 @@ struct vb2_fileio_buf {
/**
* struct vb2_fileio_data - queue context used by file io emulator
*
* @cur_index: the index of the buffer currently being read from or
* written to. If equal to q->num_buffers then a new buffer
* must be dequeued.
* @initial_index: in the read() case all buffers are queued up immediately
* in __vb2_init_fileio() and __vb2_perform_fileio() just cycles
* buffers. However, in the write() case no buffers are initially
* queued, instead whenever a buffer is full it is queued up by
* __vb2_perform_fileio(). Only once all available buffers have
* been queued up will __vb2_perform_fileio() start to dequeue
* buffers. This means that initially __vb2_perform_fileio()
* needs to know what buffer index to use when it is queuing up
* the buffers for the first time. That initial index is stored
* in this field. Once it is equal to q->num_buffers all
* available buffers have been queued and __vb2_perform_fileio()
* should start the normal dequeue/queue cycle.
*
* vb2 provides a compatibility layer and emulator of file io (read and
* write) calls on top of streaming API. For proper operation it required
* this structure to save the driver state between each call of the read
@ -2319,7 +2335,8 @@ struct vb2_fileio_data {
struct v4l2_requestbuffers req;
struct v4l2_buffer b;
struct vb2_fileio_buf bufs[VIDEO_MAX_FRAME];
unsigned int index;
unsigned int cur_index;
unsigned int initial_index;
unsigned int q_count;
unsigned int dq_count;
unsigned int flags;
@ -2419,7 +2436,12 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
goto err_reqbufs;
fileio->bufs[i].queued = 1;
}
fileio->index = q->num_buffers;
/*
* All buffers have been queued, so mark that by setting
* initial_index to q->num_buffers
*/
fileio->initial_index = q->num_buffers;
fileio->cur_index = q->num_buffers;
}
/*
@ -2498,7 +2520,7 @@ 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->cur_index;
if (index >= q->num_buffers) {
/*
* Call vb2_dqbuf to get buffer back.
@ -2512,7 +2534,7 @@ 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->cur_index = index = fileio->b.index;
buf = &fileio->bufs[index];
/*
@ -2588,8 +2610,20 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
buf->queued = 1;
buf->size = vb2_plane_size(q->bufs[index], 0);
fileio->q_count += 1;
if (fileio->index < q->num_buffers)
fileio->index++;
/*
* If we are queuing up buffers for the first time, then
* increase initial_index by one.
*/
if (fileio->initial_index < q->num_buffers)
fileio->initial_index++;
/*
* The next buffer to use is either a buffer that's going to be
* queued for the first time (initial_index < q->num_buffers)
* or it is equal to q->num_buffers, meaning that the next
* time we need to dequeue a buffer since we've now queued up
* all the 'first time' buffers.
*/
fileio->cur_index = fileio->initial_index;
}
/*