LinuxTV Patchwork [v6,05/10] media: uvcvideo: queue: Support asynchronous buffer handling

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Submitter Kieran Bingham
Date Nov. 9, 2018, 5:05 p.m.
Message ID <36fe070c8b07e0f71b276a586a06dd61dd564e05.1541782862.git-series.kieran.bingham@ideasonboard.com>
Download mbox | patch
Permalink /patch/52875/
State New
Delegated to: Laurent Pinchart
Headers show

Comments

Kieran Bingham - Nov. 9, 2018, 5:05 p.m.
The buffer queue interface currently operates sequentially, processing
buffers after they have fully completed.

In preparation for supporting parallel tasks operating on the buffers,
we will need to support buffers being processed on multiple CPUs.

Adapt the uvc_queue_next_buffer() such that a reference count tracks the
active use of the buffer, returning the buffer to the VB2 stack at
completion.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

v5:
 - uvc_queue_requeue() -> uvc_queue_buffer_requeue()
 - Fix comment
---
 drivers/media/usb/uvc/uvc_queue.c | 61 ++++++++++++++++++++++++++------
 drivers/media/usb/uvc/uvcvideo.h  |  4 ++-
 2 files changed, 54 insertions(+), 11 deletions(-)
Laurent Pinchart - Nov. 10, 2018, 4:30 p.m.
Hi Kieran,

Thank you for the patch.

On Friday, 9 November 2018 19:05:28 EET Kieran Bingham wrote:
> The buffer queue interface currently operates sequentially, processing
> buffers after they have fully completed.
> 
> In preparation for supporting parallel tasks operating on the buffers,
> we will need to support buffers being processed on multiple CPUs.
> 
> Adapt the uvc_queue_next_buffer() such that a reference count tracks the
> active use of the buffer, returning the buffer to the VB2 stack at
> completion.
> 
> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> v5:
>  - uvc_queue_requeue() -> uvc_queue_buffer_requeue()
>  - Fix comment
> ---
>  drivers/media/usb/uvc/uvc_queue.c | 61 ++++++++++++++++++++++++++------
>  drivers/media/usb/uvc/uvcvideo.h  |  4 ++-
>  2 files changed, 54 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_queue.c
> b/drivers/media/usb/uvc/uvc_queue.c index fa7059aab49a..2752e386f1e8 100644
> --- a/drivers/media/usb/uvc/uvc_queue.c
> +++ b/drivers/media/usb/uvc/uvc_queue.c
> @@ -142,6 +142,7 @@ static void uvc_buffer_queue(struct vb2_buffer *vb)
> 
>  	spin_lock_irqsave(&queue->irqlock, flags);
>  	if (likely(!(queue->flags & UVC_QUEUE_DISCONNECTED))) {
> +		kref_init(&buf->ref);
>  		list_add_tail(&buf->queue, &queue->irqqueue);
>  	} else {
>  		/* If the device is disconnected return the buffer to userspace
> @@ -458,28 +459,66 @@ struct uvc_buffer *uvc_queue_get_current_buffer(struct
> uvc_video_queue *queue) return nextbuf;
>  }
> 
> -struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
> +/*
> + * uvc_queue_buffer_requeue: Requeue a buffer on our internal irqqueue
> + *
> + * Reuse a buffer through our internal queue without the need to 'prepare'.
> + * The buffer will be returned to userspace through the uvc_buffer_queue
> call if + * the device has been disconnected.
> + */
> +static void uvc_queue_buffer_requeue(struct uvc_video_queue *queue,
>  		struct uvc_buffer *buf)
>  {
> -	struct uvc_buffer *nextbuf;
> -	unsigned long flags;
> +	buf->error = 0;
> +	buf->state = UVC_BUF_STATE_QUEUED;
> +	buf->bytesused = 0;
> +	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, 0);
> +
> +	uvc_buffer_queue(&buf->buf.vb2_buf);
> +}
> +
> +static void uvc_queue_buffer_complete(struct kref *ref)
> +{
> +	struct uvc_buffer *buf = container_of(ref, struct uvc_buffer, ref);
> +	struct vb2_buffer *vb = &buf->buf.vb2_buf;
> +	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
> 
>  	if ((queue->flags & UVC_QUEUE_DROP_CORRUPTED) && buf->error) {
> -		buf->error = 0;
> -		buf->state = UVC_BUF_STATE_QUEUED;
> -		buf->bytesused = 0;
> -		vb2_set_plane_payload(&buf->buf.vb2_buf, 0, 0);
> -		return buf;
> +		uvc_queue_buffer_requeue(queue, buf);
> +		return;
>  	}
> 
> +	buf->state = buf->error ? UVC_BUF_STATE_ERROR : UVC_BUF_STATE_DONE;
> +	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, buf->bytesused);
> +	vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_DONE);
> +}
> +
> +/*
> + * Release a reference on the buffer. Complete the buffer when the last
> + * reference is released.
> + */
> +void uvc_queue_buffer_release(struct uvc_buffer *buf)
> +{
> +	kref_put(&buf->ref, uvc_queue_buffer_complete);
> +}
> +
> +/*
> + * Remove this buffer from the queue. Lifetime will persist while async
> actions + * are still running (if any), and uvc_queue_buffer_release will
> give the buffer + * back to VB2 when all users have completed.
> + */
> +struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
> +		struct uvc_buffer *buf)
> +{
> +	struct uvc_buffer *nextbuf;
> +	unsigned long flags;
> +
>  	spin_lock_irqsave(&queue->irqlock, flags);
>  	list_del(&buf->queue);
>  	nextbuf = __uvc_queue_get_current_buffer(queue);
>  	spin_unlock_irqrestore(&queue->irqlock, flags);
> 
> -	buf->state = buf->error ? UVC_BUF_STATE_ERROR : UVC_BUF_STATE_DONE;
> -	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, buf->bytesused);
> -	vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_DONE);
> +	uvc_queue_buffer_release(buf);
> 
>  	return nextbuf;
>  }
> diff --git a/drivers/media/usb/uvc/uvcvideo.h
> b/drivers/media/usb/uvc/uvcvideo.h index 16b8348f7ff0..7f884c60ae59 100644
> --- a/drivers/media/usb/uvc/uvcvideo.h
> +++ b/drivers/media/usb/uvc/uvcvideo.h
> @@ -413,6 +413,9 @@ struct uvc_buffer {
>  	unsigned int bytesused;
> 
>  	u32 pts;
> +
> +	/* Asynchronous buffer handling. */
> +	struct kref ref;
>  };
> 
>  #define UVC_QUEUE_DISCONNECTED		(1 << 0)
> @@ -728,6 +731,7 @@ void uvc_queue_cancel(struct uvc_video_queue *queue, int
> disconnect);
> struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
> struct uvc_buffer *buf);
>  struct uvc_buffer *uvc_queue_get_current_buffer(struct uvc_video_queue
> *queue);
> +void uvc_queue_buffer_release(struct uvc_buffer *buf);
>  int uvc_queue_mmap(struct uvc_video_queue *queue,
>  		   struct vm_area_struct *vma);
>  __poll_t uvc_queue_poll(struct uvc_video_queue *queue, struct file *file,

Patch

diff --git a/drivers/media/usb/uvc/uvc_queue.c b/drivers/media/usb/uvc/uvc_queue.c
index fa7059aab49a..2752e386f1e8 100644
--- a/drivers/media/usb/uvc/uvc_queue.c
+++ b/drivers/media/usb/uvc/uvc_queue.c
@@ -142,6 +142,7 @@  static void uvc_buffer_queue(struct vb2_buffer *vb)
 
 	spin_lock_irqsave(&queue->irqlock, flags);
 	if (likely(!(queue->flags & UVC_QUEUE_DISCONNECTED))) {
+		kref_init(&buf->ref);
 		list_add_tail(&buf->queue, &queue->irqqueue);
 	} else {
 		/* If the device is disconnected return the buffer to userspace
@@ -458,28 +459,66 @@  struct uvc_buffer *uvc_queue_get_current_buffer(struct uvc_video_queue *queue)
 	return nextbuf;
 }
 
-struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
+/*
+ * uvc_queue_buffer_requeue: Requeue a buffer on our internal irqqueue
+ *
+ * Reuse a buffer through our internal queue without the need to 'prepare'.
+ * The buffer will be returned to userspace through the uvc_buffer_queue call if
+ * the device has been disconnected.
+ */
+static void uvc_queue_buffer_requeue(struct uvc_video_queue *queue,
 		struct uvc_buffer *buf)
 {
-	struct uvc_buffer *nextbuf;
-	unsigned long flags;
+	buf->error = 0;
+	buf->state = UVC_BUF_STATE_QUEUED;
+	buf->bytesused = 0;
+	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, 0);
+
+	uvc_buffer_queue(&buf->buf.vb2_buf);
+}
+
+static void uvc_queue_buffer_complete(struct kref *ref)
+{
+	struct uvc_buffer *buf = container_of(ref, struct uvc_buffer, ref);
+	struct vb2_buffer *vb = &buf->buf.vb2_buf;
+	struct uvc_video_queue *queue = vb2_get_drv_priv(vb->vb2_queue);
 
 	if ((queue->flags & UVC_QUEUE_DROP_CORRUPTED) && buf->error) {
-		buf->error = 0;
-		buf->state = UVC_BUF_STATE_QUEUED;
-		buf->bytesused = 0;
-		vb2_set_plane_payload(&buf->buf.vb2_buf, 0, 0);
-		return buf;
+		uvc_queue_buffer_requeue(queue, buf);
+		return;
 	}
 
+	buf->state = buf->error ? UVC_BUF_STATE_ERROR : UVC_BUF_STATE_DONE;
+	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, buf->bytesused);
+	vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_DONE);
+}
+
+/*
+ * Release a reference on the buffer. Complete the buffer when the last
+ * reference is released.
+ */
+void uvc_queue_buffer_release(struct uvc_buffer *buf)
+{
+	kref_put(&buf->ref, uvc_queue_buffer_complete);
+}
+
+/*
+ * Remove this buffer from the queue. Lifetime will persist while async actions
+ * are still running (if any), and uvc_queue_buffer_release will give the buffer
+ * back to VB2 when all users have completed.
+ */
+struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
+		struct uvc_buffer *buf)
+{
+	struct uvc_buffer *nextbuf;
+	unsigned long flags;
+
 	spin_lock_irqsave(&queue->irqlock, flags);
 	list_del(&buf->queue);
 	nextbuf = __uvc_queue_get_current_buffer(queue);
 	spin_unlock_irqrestore(&queue->irqlock, flags);
 
-	buf->state = buf->error ? UVC_BUF_STATE_ERROR : UVC_BUF_STATE_DONE;
-	vb2_set_plane_payload(&buf->buf.vb2_buf, 0, buf->bytesused);
-	vb2_buffer_done(&buf->buf.vb2_buf, VB2_BUF_STATE_DONE);
+	uvc_queue_buffer_release(buf);
 
 	return nextbuf;
 }
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 16b8348f7ff0..7f884c60ae59 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -413,6 +413,9 @@  struct uvc_buffer {
 	unsigned int bytesused;
 
 	u32 pts;
+
+	/* Asynchronous buffer handling. */
+	struct kref ref;
 };
 
 #define UVC_QUEUE_DISCONNECTED		(1 << 0)
@@ -728,6 +731,7 @@  void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect);
 struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
 					 struct uvc_buffer *buf);
 struct uvc_buffer *uvc_queue_get_current_buffer(struct uvc_video_queue *queue);
+void uvc_queue_buffer_release(struct uvc_buffer *buf);
 int uvc_queue_mmap(struct uvc_video_queue *queue,
 		   struct vm_area_struct *vma);
 __poll_t uvc_queue_poll(struct uvc_video_queue *queue, struct file *file,

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