[RFC PATCH 3/8] vb2: remove the 'fileio = NULL' hack.

Hans Verkuil
2013-11-21T15:22:40Z

From: Hans Verkuil <hans.verkuil@cisco.com>

The read/write implementation in vb2 reuses existing vb2 functions, but
it sets q->fileio to NULL before calling them in order to skip the
'q->fileio != NULL' check.

This works today due to the synchronous nature of read/write, but it
1) is ugly, and 2) will fail in an asynchronous use-case such as a
thread queuing and dequeuing buffers. This last example will be necessary
in order to implement vb2 DVB support.

This patch removes the hack by splitting up the dqbuf/qbuf/streamon/streamoff
functions into an external and an internal version. The external version
checks q->fileio and then calls the internal version. The read/write
implementation now just uses the internal version, removing the need to
set q->fileio to NULL.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
---
drivers/media/v4l2-core/videobuf2-core.c | 223 ++++++++++++++++---------------
1 file changed, 112 insertions(+), 111 deletions(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index e90a5be..9ea3ae9 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1261,11 +1261,6 @@ static int __buf_prepare(struct vb2_buffer *vb, const struct v4l2_buffer *b)
static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b,
const char *opname)
{
- if (q->fileio) {
- dprintk(1, "%s(): file io in progress\n", opname);
- return -EBUSY;
- }
-
if (b->type != q->type) {
dprintk(1, "%s(): invalid buffer type\n", opname);
return -EINVAL;
@@ -1307,9 +1302,15 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b,
*/
int vb2_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b)
{
- int ret = vb2_queue_or_prepare_buf(q, b, "prepare_buf");
struct vb2_buffer *vb;
+ int ret;
+
+ if (q->fileio) {
+ dprintk(1, "%s(): file io in progress\n", __func__);
+ return -EBUSY;
+ }

+ ret = vb2_queue_or_prepare_buf(q, b, "prepare_buf");
if (ret)
return ret;

@@ -1331,24 +1332,7 @@ int vb2_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b)
}
EXPORT_SYMBOL_GPL(vb2_prepare_buf);

-/**
- * vb2_qbuf() - Queue a buffer from userspace
- * @q: videobuf2 queue
- * @b: buffer structure passed from userspace to vidioc_qbuf handler
- * in driver
- *
- * Should be called from vidioc_qbuf ioctl handler of a driver.
- * This function:
- * 1) verifies the passed buffer,
- * 2) if necessary, calls buf_prepare callback in the driver (if provided), in
- * which driver-specific buffer initialization can be performed,
- * 3) if streaming is on, queues the buffer in driver by the means of buf_queue
- * callback for processing.
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_qbuf handler in driver.
- */
-int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
+static int vb2_internal_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
{
int ret = vb2_queue_or_prepare_buf(q, b, "qbuf");
struct vb2_buffer *vb;
@@ -1396,6 +1380,33 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
dprintk(1, "%s() of buffer %d succeeded\n", __func__, vb->v4l2_buf.index);
return 0;
}
+
+/**
+ * vb2_qbuf() - Queue a buffer from userspace
+ * @q: videobuf2 queue
+ * @b: buffer structure passed from userspace to vidioc_qbuf handler
+ * in driver
+ *
+ * Should be called from vidioc_qbuf ioctl handler of a driver.
+ * This function:
+ * 1) verifies the passed buffer,
+ * 2) if necessary, calls buf_prepare callback in the driver (if provided), in
+ * which driver-specific buffer initialization can be performed,
+ * 3) if streaming is on, queues the buffer in driver by the means of buf_queue
+ * callback for processing.
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_qbuf handler in driver.
+ */
+int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
+{
+ if (q->fileio) {
+ dprintk(1, "%s(): file io in progress\n", __func__);
+ return -EBUSY;
+ }
+
+ return vb2_internal_qbuf(q, b);
+}
EXPORT_SYMBOL_GPL(vb2_qbuf);

/**
@@ -1544,37 +1555,11 @@ static void __vb2_dqbuf(struct vb2_buffer *vb)
}
}

-/**
- * vb2_dqbuf() - Dequeue a buffer to the userspace
- * @q: videobuf2 queue
- * @b: buffer structure passed from userspace to vidioc_dqbuf handler
- * in driver
- * @nonblocking: if true, this call will not sleep waiting for a buffer if no
- * buffers ready for dequeuing are present. Normally the driver
- * would be passing (file->f_flags & O_NONBLOCK) here
- *
- * Should be called from vidioc_dqbuf ioctl handler of a driver.
- * This function:
- * 1) verifies the passed buffer,
- * 2) calls buf_finish callback in the driver (if provided), in which
- * driver can perform any additional operations that may be required before
- * returning the buffer to userspace, such as cache sync,
- * 3) the buffer struct members are filled with relevant information for
- * the userspace.
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_dqbuf handler in driver.
- */
-int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)
+static int vb2_internal_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)
{
struct vb2_buffer *vb = NULL;
int ret;

- if (q->fileio) {
- dprintk(1, "dqbuf: file io in progress\n");
- return -EBUSY;
- }
-
if (b->type != q->type) {
dprintk(1, "dqbuf: invalid buffer type\n");
return -EINVAL;
@@ -1613,6 +1598,36 @@ int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)

return 0;
}
+
+/**
+ * vb2_dqbuf() - Dequeue a buffer to the userspace
+ * @q: videobuf2 queue
+ * @b: buffer structure passed from userspace to vidioc_dqbuf handler
+ * in driver
+ * @nonblocking: if true, this call will not sleep waiting for a buffer if no
+ * buffers ready for dequeuing are present. Normally the driver
+ * would be passing (file->f_flags & O_NONBLOCK) here
+ *
+ * Should be called from vidioc_dqbuf ioctl handler of a driver.
+ * This function:
+ * 1) verifies the passed buffer,
+ * 2) calls buf_finish callback in the driver (if provided), in which
+ * driver can perform any additional operations that may be required before
+ * returning the buffer to userspace, such as cache sync,
+ * 3) the buffer struct members are filled with relevant information for
+ * the userspace.
+ *
+ * The return values from this function are intended to be directly returned
+ * from vidioc_dqbuf handler in driver.
+ */
+int vb2_dqbuf(struct vb2_queue *q, struct v4l2_buffer *b, bool nonblocking)
+{
+ if (q->fileio) {
+ dprintk(1, "dqbuf: file io in progress\n");
+ return -EBUSY;
+ }
+ return vb2_internal_dqbuf(q, b, nonblocking);
+}
EXPORT_SYMBOL_GPL(vb2_dqbuf);

/**
@@ -1652,29 +1667,11 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
__vb2_dqbuf(q->bufs[i]);
}

-/**
- * vb2_streamon - start streaming
- * @q: videobuf2 queue
- * @type: type argument passed from userspace to vidioc_streamon handler
- *
- * Should be called from vidioc_streamon handler of a driver.
- * This function:
- * 1) verifies current state
- * 2) passes any previously queued buffers to the driver and starts streaming
- *
- * The return values from this function are intended to be directly returned
- * from vidioc_streamon handler in the driver.
- */
-int vb2_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
+static int vb2_internal_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
{
struct vb2_buffer *vb;
int ret;

- if (q->fileio) {
- dprintk(1, "streamon: file io in progress\n");
- return -EBUSY;
- }
-
if (type != q->type) {
dprintk(1, "streamon: invalid stream type\n");
return -EINVAL;
@@ -1707,31 +1704,32 @@ int vb2_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
dprintk(3, "Streamon successful\n");
return 0;
}
-EXPORT_SYMBOL_GPL(vb2_streamon);
-

/**
- * vb2_streamoff - stop streaming
+ * vb2_streamon - start streaming
* @q: videobuf2 queue
- * @type: type argument passed from userspace to vidioc_streamoff handler
+ * @type: type argument passed from userspace to vidioc_streamon handler
*
- * Should be called from vidioc_streamoff handler of a driver.
+ * Should be called from vidioc_streamon handler of a driver.
* This function:
- * 1) verifies current state,
- * 2) stop streaming and dequeues any queued buffers, including those previously
- * passed to the driver (after waiting for the driver to finish).
+ * 1) verifies current state
+ * 2) passes any previously queued buffers to the driver and starts streaming
*
- * This call can be used for pausing playback.
* The return values from this function are intended to be directly returned
- * from vidioc_streamoff handler in the driver
+ * from vidioc_streamon handler in the driver.
*/
-int vb2_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
+int vb2_streamon(struct vb2_queue *q, enum v4l2_buf_type type)
{
if (q->fileio) {
- dprintk(1, "streamoff: file io in progress\n");
+ dprintk(1, "streamon: file io in progress\n");
return -EBUSY;
}
+ return vb2_internal_streamon(q, type);
+}
+EXPORT_SYMBOL_GPL(vb2_streamon);

+static int vb2_internal_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
+{
if (type != q->type) {
dprintk(1, "streamoff: invalid stream type\n");
return -EINVAL;
@@ -1751,6 +1749,30 @@ int vb2_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
dprintk(3, "Streamoff successful\n");
return 0;
}
+
+/**
+ * vb2_streamoff - stop streaming
+ * @q: videobuf2 queue
+ * @type: type argument passed from userspace to vidioc_streamoff handler
+ *
+ * Should be called from vidioc_streamoff handler of a driver.
+ * This function:
+ * 1) verifies current state,
+ * 2) stop streaming and dequeues any queued buffers, including those previously
+ * passed to the driver (after waiting for the driver to finish).
+ *
+ * This call can be used for pausing playback.
+ * The return values from this function are intended to be directly returned
+ * from vidioc_streamoff handler in the driver
+ */
+int vb2_streamoff(struct vb2_queue *q, enum v4l2_buf_type type)
+{
+ if (q->fileio) {
+ dprintk(1, "streamoff: file io in progress\n");
+ return -EBUSY;
+ }
+ return vb2_internal_streamoff(q, type);
+}
EXPORT_SYMBOL_GPL(vb2_streamoff);

/**
@@ -2273,13 +2295,8 @@ static int __vb2_cleanup_fileio(struct vb2_queue *q)
struct vb2_fileio_data *fileio = q->fileio;

if (fileio) {
- /*
- * Hack fileio context to enable direct calls to vb2 ioctl
- * interface.
- */
+ vb2_internal_streamoff(q, q->type);
q->fileio = NULL;
-
- vb2_streamoff(q, q->type);
fileio->req.count = 0;
vb2_reqbufs(q, &fileio->req);
kfree(fileio);
@@ -2322,12 +2339,6 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
}
fileio = q->fileio;

- /*
- * Hack fileio context to enable direct calls to vb2 ioctl interface.
- * The pointer will be restored before returning from this function.
- */
- q->fileio = NULL;
-
index = fileio->index;
buf = &fileio->bufs[index];

@@ -2344,10 +2355,10 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
fileio->b.type = q->type;
fileio->b.memory = q->memory;
fileio->b.index = index;
- ret = vb2_dqbuf(q, &fileio->b, nonblock);
+ ret = vb2_internal_dqbuf(q, &fileio->b, nonblock);
dprintk(5, "file io: vb2_dqbuf result: %d\n", ret);
if (ret)
- goto end;
+ return ret;
fileio->dq_count += 1;

/*
@@ -2377,8 +2388,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
ret = copy_from_user(buf->vaddr + buf->pos, data, count);
if (ret) {
dprintk(3, "file io: error copying data\n");
- ret = -EFAULT;
- goto end;
+ return -EFAULT;
}

/*
@@ -2398,10 +2408,6 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
if (read && (fileio->flags & VB2_FILEIO_READ_ONCE) &&
fileio->dq_count == 1) {
dprintk(3, "file io: read limit reached\n");
- /*
- * Restore fileio pointer and release the context.
- */
- q->fileio = fileio;
return __vb2_cleanup_fileio(q);
}

@@ -2413,10 +2419,10 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
fileio->b.memory = q->memory;
fileio->b.index = index;
fileio->b.bytesused = buf->pos;
- ret = vb2_qbuf(q, &fileio->b);
+ ret = vb2_internal_qbuf(q, &fileio->b);
dprintk(5, "file io: vb2_dbuf result: %d\n", ret);
if (ret)
- goto end;
+ return ret;

/*
* Buffer has been queued, update the status
@@ -2435,9 +2441,9 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
* Start streaming if required.
*/
if (!read && !q->streaming) {
- ret = vb2_streamon(q, q->type);
+ ret = vb2_internal_streamon(q, q->type);
if (ret)
- goto end;
+ return ret;
}
}

@@ -2446,11 +2452,6 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_
*/
if (ret == 0)
ret = count;
-end:
- /*
- * Restore the fileio context and block vb2 ioctl interface.
- */
- q->fileio = fileio;
return ret;
}

--
1.8.4.3