[media] uvc gadget: switch to v4l2 core locking

Switch this driver over to the V4L2 core locking mechanism in preparation
for switching to unlocked_ioctl. Suggested by Laurent Pinchart.

This patch introduces a new mutex at the struct uvc_video level and
drops the old mutex at the queue level. The new lock is now used for all
ioctl locking and in the release file operation (the driver always has
to take care of locking in file operations, the core only serializes
ioctls).

Note that the mmap and get_unmapped_area file operations no longer take
a lock. Commit f035eb4e976ef5a059e30bc91cfd310ff030a7d3 fixed a AB-BA
deadlock by moving all the locking down into vb2, so the mmap and
get_unmapped_area file operations should no longer do any locking before
calling into vb2.

Signed-off-by: Hans Verkuil <[e-mail]>
Acked-by: Laurent Pinchart <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/usb/gadget/function/f_uvc.c

···
 	video->ioctl_ops = &uvc_v4l2_ioctl_ops;
 	video->release = video_device_release;
 	video->vfl_dir = VFL_DIR_TX;
+	video->lock = &uvc->video.mutex;
 	strlcpy(video->name, cdev->gadget->name, sizeof(video->name));
 
 	uvc->vdev = video;
···
 	if (uvc == NULL)
 		return ERR_PTR(-ENOMEM);
 
+	mutex_init(&uvc->video.mutex);
 	uvc->state = UVC_STATE_DISCONNECTED;
 	opts = fi_to_f_uvc_opts(fi);
 

drivers/usb/gadget/function/uvc.h

···
 	unsigned int width;
 	unsigned int height;
 	unsigned int imagesize;
+	struct mutex mutex;	/* protects frame parameters */
 
 	/* Requests */
 	unsigned int req_size;

drivers/usb/gadget/function/uvc_queue.c

···
 	spin_unlock_irqrestore(&queue->irqlock, flags);
 }
 
-static void uvc_wait_prepare(struct vb2_queue *vq)
-{
-	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
-
-	mutex_unlock(&queue->mutex);
-}
-
-static void uvc_wait_finish(struct vb2_queue *vq)
-{
-	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
-
-	mutex_lock(&queue->mutex);
-}
-
 static struct vb2_ops uvc_queue_qops = {
 	.queue_setup = uvc_queue_setup,
 	.buf_prepare = uvc_buffer_prepare,
 	.buf_queue = uvc_buffer_queue,
-	.wait_prepare = uvc_wait_prepare,
-	.wait_finish = uvc_wait_finish,
+	.wait_prepare = vb2_ops_wait_prepare,
+	.wait_finish = vb2_ops_wait_finish,
 };
 
-int uvcg_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type)
+int uvcg_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type,
+		    struct mutex *lock)
 {
 	int ret;
 
···
 	queue->queue.drv_priv = queue;
 	queue->queue.buf_struct_size = sizeof(struct uvc_buffer);
 	queue->queue.ops = &uvc_queue_qops;
+	queue->queue.lock = lock;
 	queue->queue.mem_ops = &vb2_vmalloc_memops;
 	queue->queue.timestamp_flags = V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC
 				     | V4L2_BUF_FLAG_TSTAMP_SRC_EOF;
···
 	if (ret)
 		return ret;
 
-	mutex_init(&queue->mutex);
 	spin_lock_init(&queue->irqlock);
 	INIT_LIST_HEAD(&queue->irqqueue);
 	queue->flags = 0;
···
  */
 void uvcg_free_buffers(struct uvc_video_queue *queue)
 {
-	mutex_lock(&queue->mutex);
 	vb2_queue_release(&queue->queue);
-	mutex_unlock(&queue->mutex);
 }
 
 /*
···
 {
 	int ret;
 
-	mutex_lock(&queue->mutex);
 	ret = vb2_reqbufs(&queue->queue, rb);
-	mutex_unlock(&queue->mutex);
 
 	return ret ? ret : rb->count;
 }
 
 int uvcg_query_buffer(struct uvc_video_queue *queue, struct v4l2_buffer *buf)
 {
-	int ret;
-
-	mutex_lock(&queue->mutex);
-	ret = vb2_querybuf(&queue->queue, buf);
-	mutex_unlock(&queue->mutex);
-
-	return ret;
+	return vb2_querybuf(&queue->queue, buf);
 }
 
 int uvcg_queue_buffer(struct uvc_video_queue *queue, struct v4l2_buffer *buf)
···
 	unsigned long flags;
 	int ret;
 
-	mutex_lock(&queue->mutex);
 	ret = vb2_qbuf(&queue->queue, buf);
 	if (ret < 0)
-		goto done;
+		return ret;
 
 	spin_lock_irqsave(&queue->irqlock, flags);
 	ret = (queue->flags & UVC_QUEUE_PAUSED) != 0;
 	queue->flags &= ~UVC_QUEUE_PAUSED;
 	spin_unlock_irqrestore(&queue->irqlock, flags);
-
-done:
-	mutex_unlock(&queue->mutex);
 	return ret;
 }
 
···
 int uvcg_dequeue_buffer(struct uvc_video_queue *queue, struct v4l2_buffer *buf,
 			int nonblocking)
 {
-	int ret;
-
-	mutex_lock(&queue->mutex);
-	ret = vb2_dqbuf(&queue->queue, buf, nonblocking);
-	mutex_unlock(&queue->mutex);
-
-	return ret;
+	return vb2_dqbuf(&queue->queue, buf, nonblocking);
 }
 
 /*
···
 unsigned int uvcg_queue_poll(struct uvc_video_queue *queue, struct file *file,
 			     poll_table *wait)
 {
-	unsigned int ret;
-
-	mutex_lock(&queue->mutex);
-	ret = vb2_poll(&queue->queue, file, wait);
-	mutex_unlock(&queue->mutex);
-
-	return ret;
+	return vb2_poll(&queue->queue, file, wait);
 }
 
 int uvcg_queue_mmap(struct uvc_video_queue *queue, struct vm_area_struct *vma)
 {
-	int ret;
-
-	mutex_lock(&queue->mutex);
-	ret = vb2_mmap(&queue->queue, vma);
-	mutex_unlock(&queue->mutex);
-
-	return ret;
+	return vb2_mmap(&queue->queue, vma);
 }
 
 #ifndef CONFIG_MMU
···
 unsigned long uvcg_queue_get_unmapped_area(struct uvc_video_queue *queue,
 					   unsigned long pgoff)
 {
-	unsigned long ret;
-
-	mutex_lock(&queue->mutex);
-	ret = vb2_get_unmapped_area(&queue->queue, 0, 0, pgoff, 0);
-	mutex_unlock(&queue->mutex);
-	return ret;
+	return vb2_get_unmapped_area(&queue->queue, 0, 0, pgoff, 0);
 }
 #endif
 
···
 	unsigned long flags;
 	int ret = 0;
 
-	mutex_lock(&queue->mutex);
 	if (enable) {
 		ret = vb2_streamon(&queue->queue, queue->queue.type);
 		if (ret < 0)
-			goto done;
+			return ret;
 
 		queue->sequence = 0;
 		queue->buf_used = 0;
 	} else {
 		ret = vb2_streamoff(&queue->queue, queue->queue.type);
 		if (ret < 0)
-			goto done;
+			return ret;
 
 		spin_lock_irqsave(&queue->irqlock, flags);
 		INIT_LIST_HEAD(&queue->irqqueue);
···
 		spin_unlock_irqrestore(&queue->irqlock, flags);
 	}
 
-done:
-	mutex_unlock(&queue->mutex);
 	return ret;
 }
 

drivers/usb/gadget/function/uvc_queue.h

···
 
 struct uvc_video_queue {
 	struct vb2_queue queue;
-	struct mutex mutex;	/* Protects queue */
 
 	unsigned int flags;
 	__u32 sequence;
···
 	return vb2_is_streaming(&queue->queue);
 }
 
-int uvcg_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type);
+int uvcg_queue_init(struct uvc_video_queue *queue, enum v4l2_buf_type type,
+		    struct mutex *lock);
 
 void uvcg_free_buffers(struct uvc_video_queue *queue);
 

drivers/usb/gadget/function/uvc_v4l2.c

···
 #include <linux/device.h>
 #include <linux/errno.h>
 #include <linux/list.h>
-#include <linux/mutex.h>
 #include <linux/videodev2.h>
 #include <linux/vmalloc.h>
 #include <linux/wait.h>
···
 
 	uvc_function_disconnect(uvc);
 
+	mutex_lock(&video->mutex);
 	uvcg_video_enable(video, 0);
 	uvcg_free_buffers(&video->queue);
+	mutex_unlock(&video->mutex);
 
 	file->private_data = NULL;
 	v4l2_fh_del(&handle->vfh);

drivers/usb/gadget/function/uvc_video.c

···
 	video->imagesize = 320 * 240 * 2;
 
 	/* Initialize the video buffers queue. */
-	uvcg_queue_init(&video->queue, V4L2_BUF_TYPE_VIDEO_OUTPUT);
+	uvcg_queue_init(&video->queue, V4L2_BUF_TYPE_VIDEO_OUTPUT,
+			&video->mutex);
 	return 0;
 }