[RFT PATCH v2 3/6] uvcvideo: Protect queue internals with helper

[Kieran Bingham]

The URB completion operation obtains the current buffer by reading
directly into the queue internal interface.

Protect this queue abstraction by providing a helper
uvc_queue_get_current_buffer() which can be used by both the decode
task, and the uvc_queue_next_buffer() functions.

Signed-off-by: Kieran Bingham <kieran.bing...@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinch...@ideasonboard.com>

---

v2:
 - Fix coding style of conditional statements

 drivers/media/usb/uvc/uvc_queue.c | 33 +++++++++++++++++++++++++++-----
 drivers/media/usb/uvc/uvc_video.c |  7 +------
 drivers/media/usb/uvc/uvcvideo.h  |  2 ++-
 3 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_queue.c 
b/drivers/media/usb/uvc/uvc_queue.c
index c8d78b2f3de4..4a581d631525 100644
--- a/drivers/media/usb/uvc/uvc_queue.c
+++ b/drivers/media/usb/uvc/uvc_queue.c
@@ -399,6 +399,33 @@ void uvc_queue_cancel(struct uvc_video_queue *queue, int 
disconnect)
        spin_unlock_irqrestore(&queue->irqlock, flags);
 }
 
+/*
+ * uvc_queue_get_current_buffer: Obtain the current working output buffer
+ *
+ * Buffers may span multiple packets, and even URBs, therefore the active 
buffer
+ * remains on the queue until the EOF marker.
+ */
+static struct uvc_buffer *
+__uvc_queue_get_current_buffer(struct uvc_video_queue *queue)
+{
+       if (list_empty(&queue->irqqueue))
+               return NULL;
+
+       return list_first_entry(&queue->irqqueue, struct uvc_buffer, queue);
+}
+
+struct uvc_buffer *uvc_queue_get_current_buffer(struct uvc_video_queue *queue)
+{
+       struct uvc_buffer *nextbuf;
+       unsigned long flags;
+
+       spin_lock_irqsave(&queue->irqlock, flags);
+       nextbuf = __uvc_queue_get_current_buffer(queue);
+       spin_unlock_irqrestore(&queue->irqlock, flags);
+
+       return nextbuf;
+}
+
 struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
                struct uvc_buffer *buf)
 {
@@ -415,11 +442,7 @@ struct uvc_buffer *uvc_queue_next_buffer(struct 
uvc_video_queue *queue,
 
        spin_lock_irqsave(&queue->irqlock, flags);
        list_del(&buf->queue);
-       if (!list_empty(&queue->irqqueue))
-               nextbuf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
-                                          queue);
-       else
-               nextbuf = NULL;
+       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;
diff --git a/drivers/media/usb/uvc/uvc_video.c 
b/drivers/media/usb/uvc/uvc_video.c
index 92bd0952a66e..3878bec3276e 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1322,7 +1322,6 @@ static void uvc_video_complete(struct urb *urb)
        struct uvc_streaming *stream = uvc_urb->stream;
        struct uvc_video_queue *queue = &stream->queue;
        struct uvc_buffer *buf = NULL;
-       unsigned long flags;
        int ret;
 
        switch (urb->status) {
@@ -1343,11 +1342,7 @@ static void uvc_video_complete(struct urb *urb)
                return;
        }
 
-       spin_lock_irqsave(&queue->irqlock, flags);
-       if (!list_empty(&queue->irqqueue))
-               buf = list_first_entry(&queue->irqqueue, struct uvc_buffer,
-                                      queue);
-       spin_unlock_irqrestore(&queue->irqlock, flags);
+       buf = uvc_queue_get_current_buffer(queue);
 
        stream->decode(uvc_urb, buf);
 
diff --git a/drivers/media/usb/uvc/uvcvideo.h b/drivers/media/usb/uvc/uvcvideo.h
index 81a9a419a423..5caa1f4de3cb 100644
--- a/drivers/media/usb/uvc/uvcvideo.h
+++ b/drivers/media/usb/uvc/uvcvideo.h
@@ -692,6 +692,8 @@ extern int uvc_queue_streamon(struct uvc_video_queue *queue,
 extern int uvc_queue_streamoff(struct uvc_video_queue *queue,
                               enum v4l2_buf_type type);
 extern void uvc_queue_cancel(struct uvc_video_queue *queue, int disconnect);
+extern struct uvc_buffer *
+               uvc_queue_get_current_buffer(struct uvc_video_queue *queue);
 extern struct uvc_buffer *uvc_queue_next_buffer(struct uvc_video_queue *queue,
                struct uvc_buffer *buf);
 extern int uvc_queue_mmap(struct uvc_video_queue *queue,
-- 
git-series 0.9.1