[media] v4l2: use new flag to enable core priority handling

Rather than guess which driver supports core priority handling, require drivers
that do to explicitly set the V4L2_FL_USE_FH_PRIO flag in video_device.

Updated the core prio handling accordingly and set the flag in the three
drivers that do.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/video4linux/v4l2-framework.txt

@@ -577,6 +577,10 @@ You should also set these fields:
   (cx8802). Since the v4l2_device cannot be associated with a particular
   PCI device it is setup without a parent device. But when the struct
   video_device is setup you do know which parent PCI device to use.
+- flags: optional. Set to V4L2_FL_USE_FH_PRIO if you want to let the framework
+  handle the VIDIOC_G/S_PRIORITY ioctls. This requires that you use struct
+  v4l2_fh. Eventually this flag will disappear once all drivers use the core
+  priority handling. But for now it has to be set explicitly.
 
 If you use v4l2_ioctl_ops, then you should set .unlocked_ioctl to video_ioctl2
 in your v4l2_file_operations struct.
@@ -775,7 +779,8 @@ struct v4l2_fh
 
 struct v4l2_fh provides a way to easily keep file handle specific data
 that is used by the V4L2 framework. New drivers must use struct v4l2_fh
-since it is also used to implement priority handling (VIDIOC_G/S_PRIORITY).
+since it is also used to implement priority handling (VIDIOC_G/S_PRIORITY)
+if the video_device flag V4L2_FL_USE_FH_PRIO is also set.
 
 The users of v4l2_fh (in the V4L2 framework, not the driver) know
 whether a driver uses v4l2_fh as its file->private_data pointer by

drivers/media/video/cx18/cx18-streams.c

@@ -207,6 +207,7 @@ static int cx18_prep_dev(struct cx18 *cx, int type)
 	s->video_dev->fops = &cx18_v4l2_enc_fops;
 	s->video_dev->release = video_device_release;
 	s->video_dev->tvnorms = V4L2_STD_ALL;
+	set_bit(V4L2_FL_USE_FH_PRIO, &s->video_dev->flags);
 	cx18_set_funcs(s->video_dev);
 	return 0;
 }

drivers/media/video/ivtv/ivtv-streams.c

@@ -214,6 +214,7 @@ static int ivtv_prep_dev(struct ivtv *itv, int type)
 	s->vdev->fops = ivtv_stream_info[type].fops;
 	s->vdev->release = video_device_release;
 	s->vdev->tvnorms = V4L2_STD_ALL;
+	set_bit(V4L2_FL_USE_FH_PRIO, &s->vdev->flags);
 	ivtv_set_funcs(s->vdev);
 	return 0;
 }

drivers/media/video/v4l2-dev.c

@@ -578,11 +578,9 @@ int __video_register_device(struct video_device *vdev, int type, int nr,
 			vdev->parent = vdev->v4l2_dev->dev;
 		if (vdev->ctrl_handler == NULL)
 			vdev->ctrl_handler = vdev->v4l2_dev->ctrl_handler;
-		/* If the prio state pointer is NULL, and if the driver doesn't
-		   handle priorities itself, then use the v4l2_device prio
-		   state. */
-		if (vdev->prio == NULL && vdev->ioctl_ops &&
-				vdev->ioctl_ops->vidioc_s_priority == NULL)
+		/* If the prio state pointer is NULL, then use the v4l2_device
+		   prio state. */
+		if (vdev->prio == NULL)
 			vdev->prio = &vdev->v4l2_dev->prio;
 	}
 

drivers/media/video/v4l2-fh.c

@@ -35,7 +35,6 @@ int v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev)
 	INIT_LIST_HEAD(&fh->list);
 	set_bit(V4L2_FL_USES_V4L2_FH, &fh->vdev->flags);
 	fh->prio = V4L2_PRIORITY_UNSET;
-	BUG_ON(vdev->prio == NULL);
 
 	/*
 	 * fh->events only needs to be initialized if the driver
@@ -54,7 +53,8 @@ void v4l2_fh_add(struct v4l2_fh *fh)
 {
 	unsigned long flags;
 
-	v4l2_prio_open(fh->vdev->prio, &fh->prio);
+	if (test_bit(V4L2_FL_USE_FH_PRIO, &fh->vdev->flags))
+		v4l2_prio_open(fh->vdev->prio, &fh->prio);
 	spin_lock_irqsave(&fh->vdev->fh_lock, flags);
 	list_add(&fh->list, &fh->vdev->fh_list);
 	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
@@ -82,7 +82,8 @@ void v4l2_fh_del(struct v4l2_fh *fh)
 	spin_lock_irqsave(&fh->vdev->fh_lock, flags);
 	list_del_init(&fh->list);
 	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
-	v4l2_prio_close(fh->vdev->prio, fh->prio);
+	if (test_bit(V4L2_FL_USE_FH_PRIO, &fh->vdev->flags))
+		v4l2_prio_close(fh->vdev->prio, fh->prio);
 }
 EXPORT_SYMBOL_GPL(v4l2_fh_del);
 

drivers/media/video/v4l2-ioctl.c

@@ -541,6 +541,7 @@ static long __video_do_ioctl(struct file *file,
 	void *fh = file->private_data;
 	struct v4l2_fh *vfh = NULL;
 	struct v4l2_format f_copy;
+	int use_fh_prio = 0;
 	long ret = -EINVAL;
 
 	if (ops == NULL) {
@@ -555,10 +556,12 @@ static long __video_do_ioctl(struct file *file,
 		printk(KERN_CONT "\n");
 	}
 
-	if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags))
+	if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags)) {
 		vfh = file->private_data;
+		use_fh_prio = test_bit(V4L2_FL_USE_FH_PRIO, &vfd->flags);
+	}
 
-	if (vfh && !ops->vidioc_s_priority) {
+	if (use_fh_prio) {
 		switch (cmd) {
 		case VIDIOC_S_CTRL:
 		case VIDIOC_S_STD:
@@ -620,7 +623,7 @@ static long __video_do_ioctl(struct file *file,
 
 		if (ops->vidioc_g_priority) {
 			ret = ops->vidioc_g_priority(file, fh, p);
-		} else if (vfh) {
+		} else if (use_fh_prio) {
 			*p = v4l2_prio_max(&vfd->v4l2_dev->prio);
 			ret = 0;
 		}
@@ -632,7 +635,7 @@ static long __video_do_ioctl(struct file *file,
 	{
 		enum v4l2_priority *p = arg;
 
-		if (!ops->vidioc_s_priority && vfh == NULL)
+		if (!ops->vidioc_s_priority && !use_fh_prio)
 				break;
 		dbgarg(cmd, "setting priority to %d\n", *p);
 		if (ops->vidioc_s_priority)
@@ -2187,7 +2190,7 @@ static long __video_do_ioctl(struct file *file,
 
 		if (!ops->vidioc_default)
 			break;
-		if (vfh && !ops->vidioc_s_priority)
+		if (use_fh_prio)
 			valid_prio = v4l2_prio_check(vfd->prio, vfh->prio) >= 0;
 		ret = ops->vidioc_default(file, fh, valid_prio, cmd, arg);
 		break;

drivers/media/video/vivi.c

@@ -1254,6 +1254,7 @@ static int __init vivi_create_instance(int inst)
 	*vfd = vivi_template;
 	vfd->debug = debug;
 	vfd->v4l2_dev = &dev->v4l2_dev;
+	set_bit(V4L2_FL_USE_FH_PRIO, &vfd->flags);
 
 	/*
 	 * Provide a mutex to v4l2 core. It will be used to protect

include/media/v4l2-dev.h

@@ -35,7 +35,10 @@ struct v4l2_ctrl_handler;
    Drivers can clear this flag if they want to block all future
    device access. It is cleared by video_unregister_device. */
 #define V4L2_FL_REGISTERED	(0)
+/* file->private_data points to struct v4l2_fh */
 #define V4L2_FL_USES_V4L2_FH	(1)
+/* Use the prio field of v4l2_fh for core priority checking */
+#define V4L2_FL_USE_FH_PRIO	(2)
 
 /* Priority helper functions */