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Subject[RFCv3 03/17] media: videobuf2: add support for requests
Date
Make vb2 aware of requests. Drivers can specify whether a given queue
can accept requests or not. Queues that accept requests will block on a
buffer that is part of a request until that request is submitted.

Signed-off-by: Alexandre Courbot <acourbot@chromium.org>
---
drivers/media/common/videobuf2/videobuf2-core.c | 133 ++++++++++++++++++++++--
drivers/media/common/videobuf2/videobuf2-v4l2.c | 28 ++++-
include/media/videobuf2-core.h | 15 ++-
3 files changed, 168 insertions(+), 8 deletions(-)

diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
index f7109f827f6e..c1b9ccbdecb3 100644
--- a/drivers/media/common/videobuf2/videobuf2-core.c
+++ b/drivers/media/common/videobuf2/videobuf2-core.c
@@ -28,6 +28,7 @@

#include <media/videobuf2-core.h>
#include <media/v4l2-mc.h>
+#include <media/media-request.h>

#include <trace/events/vb2.h>

@@ -930,6 +931,17 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
vb->state = state;
}
atomic_dec(&q->owned_by_drv_count);
+ if (vb->request) {
+ struct media_request *req = vb->request;
+
+ if (atomic_dec_and_test(&req->buf_cpt))
+ media_request_complete(vb->request);
+
+ /* release reference acquired during qbuf */
+ vb->request = NULL;
+ media_request_put(req);
+ }
+
spin_unlock_irqrestore(&q->done_lock, flags);

trace_vb2_buf_done(q, vb);
@@ -1306,6 +1318,53 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
}
EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);

+/*
+ * vb2_check_buf_req_status() - Validate request state of a buffer
+ * @vb: buffer to check
+ *
+ * Returns true if a buffer is ready to be passed to the driver request-wise.
+ * This means that neither this buffer nor any previously-queued buffer is
+ * associated to a request that is not yet submitted.
+ *
+ * If this function returns false, then the buffer shall not be passed to its
+ * driver since the request state is not completely built yet. In that case,
+ * this function will register a notifier to be called when the request is
+ * submitted and the queue can be unblocked.
+ *
+ * This function must be called with req_lock held.
+ */
+static bool vb2_check_buf_req_status(struct vb2_buffer *vb)
+{
+ struct media_request *req = vb->request;
+ struct vb2_queue *q = vb->vb2_queue;
+ int ret = false;
+
+ mutex_lock(&q->req_lock);
+
+ if (!req) {
+ ret = !q->waiting_req;
+ goto done;
+ }
+
+ mutex_lock(&req->lock);
+ if (req->state == MEDIA_REQUEST_STATE_SUBMITTED) {
+ mutex_unlock(&req->lock);
+ ret = !q->waiting_req;
+ goto done;
+ }
+
+ if (!q->waiting_req) {
+ q->waiting_req = true;
+ atomic_notifier_chain_register(&req->submit_notif,
+ &q->req_blk);
+ }
+ mutex_unlock(&req->lock);
+
+done:
+ mutex_unlock(&q->req_lock);
+ return ret;
+}
+
/*
* vb2_start_streaming() - Attempt to start streaming.
* @q: videobuf2 queue
@@ -1326,8 +1385,11 @@ static int vb2_start_streaming(struct vb2_queue *q)
* If any buffers were queued before streamon,
* we can now pass them to driver for processing.
*/
- list_for_each_entry(vb, &q->queued_list, queued_entry)
+ list_for_each_entry(vb, &q->queued_list, queued_entry) {
+ if (!vb2_check_buf_req_status(vb))
+ break;
__enqueue_in_driver(vb);
+ }

/* Tell the driver to start streaming */
q->start_streaming_called = 1;
@@ -1369,7 +1431,46 @@ static int vb2_start_streaming(struct vb2_queue *q)
return ret;
}

-int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
+/*
+ * vb2_unblock_requests() - unblock a queue waiting for a request submission
+ * @nb: notifier block that has been registered
+ * @action: unused
+ * @data: request that has been submitted
+ *
+ * This is a callback function that is registered when
+ * vb2_check_buf_req_status() returns false. It is invoked when the request
+ * blocking the queue has been submitted. This means its buffers (and all
+ * following valid buffers) can be passed to drivers.
+ */
+static int vb2_unblock_requests(struct notifier_block *nb, unsigned long action,
+ void *data)
+{
+ struct vb2_queue *q = container_of(nb, struct vb2_queue, req_blk);
+ struct media_request *req = data;
+ struct vb2_buffer *vb;
+ bool found_request = false;
+
+ mutex_lock(&q->req_lock);
+ atomic_notifier_chain_unregister(&req->submit_notif, &q->req_blk);
+ q->waiting_req = false;
+ mutex_unlock(&q->req_lock);
+
+ list_for_each_entry(vb, &q->queued_list, queued_entry) {
+ /* All buffers before our request are already passed to the driver */
+ if (!found_request && vb->request != req)
+ continue;
+ found_request = true;
+
+ if (!vb2_check_buf_req_status(vb))
+ break;
+ __enqueue_in_driver(vb);
+ }
+
+ return 0;
+}
+
+int vb2_core_qbuf(struct vb2_queue *q, unsigned int index,
+ struct media_request *req, void *pb)
{
struct vb2_buffer *vb;
int ret;
@@ -1392,6 +1493,24 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
return -EINVAL;
}

+ vb->request = req;
+ if (req) {
+ struct vb2_buffer *_vb;
+
+ /* does the queue support requests? */
+ if (!q->allow_requests)
+ return -EINVAL;
+
+ /* do we already have a buffer for this request in the queue? */
+ list_for_each_entry(_vb, &q->queued_list, queued_entry)
+ if (_vb->request == req)
+ return -EBUSY;
+
+ /* make sure the request stays alive as long as we need */
+ media_request_get(req);
+ atomic_inc(&req->buf_cpt);
+ }
+
/*
* Add to the queued buffers list, a buffer will stay on it until
* dequeued in dqbuf.
@@ -1410,7 +1529,7 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb)
* If already streaming, give the buffer to driver for processing.
* If not, the buffer will be given to driver on next streamon.
*/
- if (q->start_streaming_called)
+ if (q->start_streaming_called && vb2_check_buf_req_status(vb))
__enqueue_in_driver(vb);

/* Fill buffer information for the userspace */
@@ -2004,6 +2123,8 @@ int vb2_core_queue_init(struct vb2_queue *q)
spin_lock_init(&q->done_lock);
mutex_init(&q->mmap_lock);
init_waitqueue_head(&q->done_wq);
+ mutex_init(&q->req_lock);
+ q->req_blk.notifier_call = vb2_unblock_requests;

q->memory = VB2_MEMORY_UNKNOWN;

@@ -2255,7 +2376,7 @@ static int __vb2_init_fileio(struct vb2_queue *q, int read)
* Queue all buffers.
*/
for (i = 0; i < q->num_buffers; i++) {
- ret = vb2_core_qbuf(q, i, NULL);
+ ret = vb2_core_qbuf(q, i, NULL, NULL);
if (ret)
goto err_reqbufs;
fileio->bufs[i].queued = 1;
@@ -2434,7 +2555,7 @@ static size_t __vb2_perform_fileio(struct vb2_queue *q, char __user *data, size_

if (copy_timestamp)
b->timestamp = ktime_get_ns();
- ret = vb2_core_qbuf(q, index, NULL);
+ ret = vb2_core_qbuf(q, index, NULL, NULL);
dprintk(5, "vb2_dbuf result: %d\n", ret);
if (ret)
return ret;
@@ -2537,7 +2658,7 @@ static int vb2_thread(void *data)
if (copy_timestamp)
vb->timestamp = ktime_get_ns();
if (!threadio->stop)
- ret = vb2_core_qbuf(q, vb->index, NULL);
+ ret = vb2_core_qbuf(q, vb->index, NULL, NULL);
call_void_qop(q, wait_prepare, q);
if (ret || threadio->stop)
break;
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index 0034f4d190f2..69286e7f9dd0 100644
--- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
@@ -30,6 +30,7 @@
#include <media/v4l2-common.h>

#include <media/videobuf2-v4l2.h>
+#include <media/media-request.h>

static int debug;
module_param(debug, int, 0644);
@@ -563,6 +564,7 @@ EXPORT_SYMBOL_GPL(vb2_create_bufs);

int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
{
+ struct media_request *req = NULL;
int ret;

if (vb2_fileio_is_active(q)) {
@@ -570,8 +572,32 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
return -EBUSY;
}

+ /*
+ * The caller should have validated that the request is valid,
+ * so we just need to look it up without further checking
+ */
+ if (b->request_fd > 0) {
+ req = media_request_get_from_fd(b->request_fd);
+ if (!req)
+ return -EINVAL;
+
+ mutex_lock(&req->lock);
+ if (req->state != MEDIA_REQUEST_STATE_IDLE) {
+ mutex_unlock(&req->lock);
+ media_request_put(req);
+ return -EINVAL;
+ }
+ mutex_unlock(&req->lock);
+ }
+
ret = vb2_queue_or_prepare_buf(q, b, "qbuf");
- return ret ? ret : vb2_core_qbuf(q, b->index, b);
+ if (!ret)
+ ret = vb2_core_qbuf(q, b->index, req, b);
+
+ if (req)
+ media_request_put(req);
+
+ return ret;
}
EXPORT_SYMBOL_GPL(vb2_qbuf);

diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index f3ee4c7c2fb3..ddd793e73022 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -238,6 +238,7 @@ struct vb2_queue;
* @num_planes: number of planes in the buffer
* on an internal driver queue.
* @timestamp: frame timestamp in ns.
+ * @request: request the buffer belongs to, if any.
*/
struct vb2_buffer {
struct vb2_queue *vb2_queue;
@@ -246,6 +247,7 @@ struct vb2_buffer {
unsigned int memory;
unsigned int num_planes;
u64 timestamp;
+ struct media_request *request;

/* private: internal use only
*
@@ -446,6 +448,7 @@ struct vb2_buf_ops {
* @quirk_poll_must_check_waiting_for_buffers: Return %POLLERR at poll when QBUF
* has not been called. This is a vb1 idiom that has been adopted
* also by vb2.
+ * @allow_requests: whether requests are supported on this queue.
* @lock: pointer to a mutex that protects the &struct vb2_queue. The
* driver can set this to a mutex to let the v4l2 core serialize
* the queuing ioctls. If the driver wants to handle locking
@@ -502,6 +505,9 @@ struct vb2_buf_ops {
* when a buffer with the %V4L2_BUF_FLAG_LAST is dequeued.
* @fileio: file io emulator internal data, used only if emulator is active
* @threadio: thread io internal data, used only if thread is active
+ * @req_lock: protects req_blk and waiting_req
+ * @req_blk: notifier to be called when waiting for a request to be submitted
+ * @waiting_req:whether this queue is currently waiting on a request submission
*/
struct vb2_queue {
unsigned int type;
@@ -513,6 +519,7 @@ struct vb2_queue {
unsigned fileio_write_immediately:1;
unsigned allow_zero_bytesused:1;
unsigned quirk_poll_must_check_waiting_for_buffers:1;
+ unsigned allow_requests:1;

struct mutex *lock;
void *owner;
@@ -556,6 +563,10 @@ struct vb2_queue {
struct vb2_fileio_data *fileio;
struct vb2_threadio_data *threadio;

+ struct mutex req_lock;
+ struct notifier_block req_blk;
+ bool waiting_req;
+
#ifdef CONFIG_VIDEO_ADV_DEBUG
/*
* Counters for how often these queue-related ops are
@@ -743,6 +754,7 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
*
* @q: pointer to &struct vb2_queue with videobuf2 queue.
* @index: id number of the buffer
+ * @req: request this buffer belongs to, if any
* @pb: buffer structure passed from userspace to
* v4l2_ioctl_ops->vidioc_qbuf handler in driver
*
@@ -759,7 +771,8 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);
*
* Return: returns zero on success; an error code otherwise.
*/
-int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb);
+int vb2_core_qbuf(struct vb2_queue *q, unsigned int index,
+ struct media_request *req, void *pb);

/**
* vb2_core_dqbuf() - Dequeue a buffer to the userspace
--
2.16.0.rc1.238.g530d649a79-goog
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