From 4e5a4d8a8e970bd6b96c1c710cd636770b776697 Mon Sep 17 00:00:00 2001 From: Hans Verkuil Date: Fri, 14 Feb 2014 06:46:50 -0300 Subject: [PATCH] [media] vb2: fix read/write regression 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 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 Tested-by: Hans Verkuil Cc: Andy Walls Signed-off-by: Mauro Carvalho Chehab --- drivers/media/v4l2-core/videobuf2-core.c | 46 ++++++++++++++++++++---- 1 file changed, 40 insertions(+), 6 deletions(-) diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c index 3c07534e9ba5..dbc2b8ab8cdb 100644 --- a/drivers/media/v4l2-core/videobuf2-core.c +++ b/drivers/media/v4l2-core/videobuf2-core.c @@ -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; } /* -- 2.39.2