[PATCH v7 5/6] [media] vb2: add out-fence support to QBUF

From: Gustavo Padovan
Date: Wed Jan 10 2018 - 11:10:52 EST

From: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>

If V4L2_BUF_FLAG_OUT_FENCE flag is present on the QBUF call we create
an out_fence and send its fd to userspace on the fence_fd field as a
return arg for the QBUF call.

The fence is signaled on buffer_done(), when the job on the buffer is
finished.

v8:
- return 0 as fence_fd if OUT_FENCE flag not used (Mauro)
- fix crash when checking not using fences in vb2_buffer_done()

v7:
- merge patch that add the infrastructure to out-fences into
this one (Alex Courbot)
- Do not install the fd if there is no fence. (Alex Courbot)
- do not report error on requeueing, just WARN_ON_ONCE() (Hans)

v6
- get rid of the V4L2_EVENT_OUT_FENCE event. We always keep the
ordering in vb2 for queueing in the driver, so the event is not
necessary anymore and the out_fence_fd is sent back to userspace
on QBUF call return arg
- do not allow requeueing with out-fences, instead mark the buffer
with an error and wake up to userspace.
- send the out_fence_fd back to userspace on the fence_fd field

v5:
- delay fd_install to DQ_EVENT (Hans)
- if queue is fully ordered send OUT_FENCE event right away
(Brian)
- rename 'q->ordered' to 'q->ordered_in_driver'
- merge change to implement OUT_FENCE event here

v4:
- return the out_fence_fd in the BUF_QUEUED event(Hans)

v3: - add WARN_ON_ONCE(q->ordered) on requeueing (Hans)
- set the OUT_FENCE flag if there is a fence pending (Hans)
- call fd_install() after vb2_core_qbuf() (Hans)
- clean up fence if vb2_core_qbuf() fails (Hans)
- add list to store sync_file and fence for the next queued buffer

v2: check if the queue is ordered.

Signed-off-by: Gustavo Padovan <gustavo.padovan@xxxxxxxxxxxxx>
---
drivers/media/common/videobuf/videobuf2-core.c | 101 +++++++++++++++++++++++--
drivers/media/common/videobuf/videobuf2-v4l2.c | 28 ++++++-
include/media/videobuf2-core.h | 22 ++++++
3 files changed, 140 insertions(+), 11 deletions(-)

diff --git a/drivers/media/common/videobuf/videobuf2-core.c b/drivers/media/common/videobuf/videobuf2-core.c
index 777e3a2bc746..1f30d9efb7c8 100644
--- a/drivers/media/common/videobuf/videobuf2-core.c
+++ b/drivers/media/common/videobuf/videobuf2-core.c
@@ -25,6 +25,7 @@
#include <linux/sched.h>
#include <linux/freezer.h>
#include <linux/kthread.h>
+#include <linux/sync_file.h>

#include <media/videobuf2-core.h>
#include <media/v4l2-mc.h>
@@ -357,6 +358,7 @@ static int __vb2_queue_alloc(struct vb2_queue *q, enum vb2_memory memory,
vb->planes[plane].length = plane_sizes[plane];
vb->planes[plane].min_length = plane_sizes[plane];
}
+ vb->out_fence_fd = -1;
q->bufs[vb->index] = vb;

/* Allocate video buffer memory for the MMAP type */
@@ -939,10 +941,22 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum vb2_buffer_state state)
case VB2_BUF_STATE_QUEUED:
break;
case VB2_BUF_STATE_REQUEUEING:
+ /* Requeuing with explicit synchronization, spit warning */
+ WARN_ON_ONCE(vb->out_fence);
+
if (q->start_streaming_called)
__enqueue_in_driver(vb);
- return;
+ break;
default:
+ if (vb->out_fence) {
+ if (state == VB2_BUF_STATE_ERROR)
+ dma_fence_set_error(vb->out_fence, -EFAULT);
+ dma_fence_signal(vb->out_fence);
+ dma_fence_put(vb->out_fence);
+ vb->out_fence = NULL;
+ vb->out_fence_fd = -1;
+ }
+
/* Inform any processes that may be waiting for buffers */
wake_up(&q->done_wq);
break;
@@ -1341,6 +1355,65 @@ int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb)
}
EXPORT_SYMBOL_GPL(vb2_core_prepare_buf);

+static inline const char *vb2_fence_get_driver_name(struct dma_fence *fence)
+{
+ return "vb2_fence";
+}
+
+static inline const char *vb2_fence_get_timeline_name(struct dma_fence *fence)
+{
+ return "vb2_fence_timeline";
+}
+
+static inline bool vb2_fence_enable_signaling(struct dma_fence *fence)
+{
+ return true;
+}
+
+static const struct dma_fence_ops vb2_fence_ops = {
+ .get_driver_name = vb2_fence_get_driver_name,
+ .get_timeline_name = vb2_fence_get_timeline_name,
+ .enable_signaling = vb2_fence_enable_signaling,
+ .wait = dma_fence_default_wait,
+};
+
+int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index)
+{
+ struct vb2_buffer *vb;
+ u64 context;
+
+ vb = q->bufs[index];
+
+ vb->out_fence_fd = get_unused_fd_flags(O_CLOEXEC);
+
+ if (call_qop(q, is_unordered, q))
+ context = dma_fence_context_alloc(1);
+ else
+ context = q->out_fence_context;
+
+ vb->out_fence = kzalloc(sizeof(*vb->out_fence), GFP_KERNEL);
+ if (!vb->out_fence)
+ return -ENOMEM;
+
+ dma_fence_init(vb->out_fence, &vb2_fence_ops, &q->out_fence_lock,
+ context, 1);
+ if (!vb->out_fence) {
+ put_unused_fd(vb->out_fence_fd);
+ return -ENOMEM;
+ }
+
+ vb->sync_file = sync_file_create(vb->out_fence);
+ if (!vb->sync_file) {
+ put_unused_fd(vb->out_fence_fd);
+ dma_fence_put(vb->out_fence);
+ vb->out_fence = NULL;
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(vb2_setup_out_fence);
+
/*
* vb2_start_streaming() - Attempt to start streaming.
* @q: videobuf2 queue
@@ -1489,18 +1562,16 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
if (vb->in_fence) {
ret = dma_fence_add_callback(vb->in_fence, &vb->fence_cb,
vb2_qbuf_fence_cb);
- if (ret == -EINVAL) {
+ /* is the fence signaled? */
+ if (ret == -ENOENT) {
+ dma_fence_put(vb->in_fence);
+ vb->in_fence = NULL;
+ } else if (ret) {
spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
goto err;
- } else if (!ret) {
- goto fill;
}
-
- dma_fence_put(vb->in_fence);
- vb->in_fence = NULL;
}

-fill:
/*
* If already streaming and there is no fence to wait on
* give the buffer to driver for processing.
@@ -1535,6 +1606,11 @@ int vb2_core_qbuf(struct vb2_queue *q, unsigned int index, void *pb,
if (pb)
call_void_bufop(q, fill_user_buffer, vb, pb);

+ if (vb->out_fence) {
+ fd_install(vb->out_fence_fd, vb->sync_file->file);
+ vb->sync_file = NULL;
+ }
+
dprintk(2, "qbuf of buffer %d succeeded\n", vb->index);
return 0;

@@ -1802,6 +1878,12 @@ static void __vb2_queue_cancel(struct vb2_queue *q)
spin_unlock_irqrestore(&vb->fence_cb_lock, flags);
}

+ /*
+ * Renew out-fence context.
+ */
+ if (!call_qop(q, is_unordered, q))
+ q->out_fence_context = dma_fence_context_alloc(1);
+
/*
* Remove all buffers from videobuf's list...
*/
@@ -2134,6 +2216,9 @@ 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);
+ if (!call_qop(q, is_unordered, q))
+ q->out_fence_context = dma_fence_context_alloc(1);
+ spin_lock_init(&q->out_fence_lock);

q->memory = VB2_MEMORY_UNKNOWN;

diff --git a/drivers/media/common/videobuf/videobuf2-v4l2.c b/drivers/media/common/videobuf/videobuf2-v4l2.c
index 0a41e3bb7733..f1291c25323f 100644
--- a/drivers/media/common/videobuf/videobuf2-v4l2.c
+++ b/drivers/media/common/videobuf/videobuf2-v4l2.c
@@ -179,12 +179,16 @@ static int vb2_queue_or_prepare_buf(struct vb2_queue *q, struct v4l2_buffer *b,
return -EINVAL;
}

- if ((b->fence_fd != 0 && b->fence_fd != -1) &&
- !(b->flags & V4L2_BUF_FLAG_IN_FENCE)) {
+ if (b->fence_fd > 0 && !(b->flags & V4L2_BUF_FLAG_IN_FENCE)) {
dprintk(1, "%s: fence_fd set without IN_FENCE flag\n", opname);
return -EINVAL;
}

+ if (b->fence_fd == -1 && (b->flags & V4L2_BUF_FLAG_IN_FENCE)) {
+ dprintk(1, "%s: IN_FENCE flag set but no fence_fd\n", opname);
+ return -EINVAL;
+ }
+
return __verify_planes_array(q->bufs[b->index], b);
}

@@ -212,7 +216,12 @@ static void __fill_v4l2_buffer(struct vb2_buffer *vb, void *pb)
b->sequence = vbuf->sequence;
b->reserved = 0;

- b->fence_fd = 0;
+ if (b->flags & V4L2_BUF_FLAG_OUT_FENCE) {
+ b->fence_fd = vb->out_fence_fd;
+ } else {
+ b->fence_fd = 0;
+ }
+
if (vb->in_fence)
b->flags |= V4L2_BUF_FLAG_IN_FENCE;
else
@@ -491,6 +500,10 @@ int vb2_querybuf(struct vb2_queue *q, struct v4l2_buffer *b)
ret = __verify_planes_array(vb, b);
if (!ret)
vb2_core_querybuf(q, b->index, b);
+
+ /* Do not return the out-fence fd on querybuf */
+ if (vb->out_fence)
+ b->fence_fd = -1;
return ret;
}
EXPORT_SYMBOL(vb2_querybuf);
@@ -595,6 +608,15 @@ int vb2_qbuf(struct vb2_queue *q, struct v4l2_buffer *b)
}
}

+ if (b->flags & V4L2_BUF_FLAG_OUT_FENCE) {
+ ret = vb2_setup_out_fence(q, b->index);
+ if (ret) {
+ dprintk(1, "failed to set up out-fence\n");
+ dma_fence_put(fence);
+ return ret;
+ }
+ }
+
return vb2_core_qbuf(q, b->index, b, fence);
}
EXPORT_SYMBOL_GPL(vb2_qbuf);
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index 0a2b1ac12dd0..260435dfc301 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -260,6 +260,10 @@ struct vb2_buffer {
* using the buffer (queueing to the driver)
* fence_cb: fence callback information
* fence_cb_lock: protect callback signal/remove
+ * out_fence_fd: the out_fence_fd to be shared with userspace.
+ * out_fence: the out-fence associated with the buffer once
+ * it is queued to the driver.
+ * sync_file: the sync file to wrap the out fence
*/
enum vb2_buffer_state state;

@@ -271,6 +275,10 @@ struct vb2_buffer {
struct dma_fence_cb fence_cb;
spinlock_t fence_cb_lock;

+ int out_fence_fd;
+ struct dma_fence *out_fence;
+ struct sync_file *sync_file;
+
#ifdef CONFIG_VIDEO_ADV_DEBUG
/*
* Counters for how often these buffer-related ops are
@@ -514,6 +522,7 @@ struct vb2_buf_ops {
* @last_buffer_dequeued: used in poll() and DQBUF to immediately return if the
* last decoded buffer was already dequeued. Set for capture queues
* when a buffer with the %V4L2_BUF_FLAG_LAST is dequeued.
+ * @out_fence_context: the fence context for the out fences
* @fileio: file io emulator internal data, used only if emulator is active
* @threadio: thread io internal data, used only if thread is active
*/
@@ -567,6 +576,9 @@ struct vb2_queue {
unsigned int copy_timestamp:1;
unsigned int last_buffer_dequeued:1;

+ u64 out_fence_context;
+ spinlock_t out_fence_lock;
+
struct vb2_fileio_data *fileio;
struct vb2_threadio_data *threadio;

@@ -753,6 +765,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
*/
int vb2_core_prepare_buf(struct vb2_queue *q, unsigned int index, void *pb);

+/**
+ * vb2_setup_out_fence() - setup new out-fence
+ * @q: The vb2_queue where to setup it
+ * @index: index of the buffer
+ *
+ * Setup the file descriptor, the fence and the sync_file for the next
+ * buffer to be queued and add everything to the tail of the q->out_fence_list.
+ */
+int vb2_setup_out_fence(struct vb2_queue *q, unsigned int index);
+
/**
* vb2_core_qbuf() - Queue a buffer from userspace
*
--
2.14.3