V4L/DVB (12744): em28xx: restructure fh/dev locking to handle both video and vbi

The current locking infrastructure didn't support having multiple fds accessing
the device (such as video and vbi).  Rework the locking infrastructure,
borrowing the design from cx88.

This work was sponsored by EyeMagnet Limited.

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 94 insertions, 88 deletions

diff --git a/drivers/media/video/em28xx/em28xx-video.c b/drivers/media/video/em28xx/em28xx-video.c
index 55bc8ea5609..dda4a76dcab 100644
--- a/drivers/media/video/em28xx/em28xx-video.c
+++ b/drivers/media/video/em28xx/em28xx-video.c
@@ -833,34 +833,63 @@ static void video_mux(struct em28xx *dev, int index)
 }
 
 /* Usage lock check functions */
-static int res_get(struct em28xx_fh *fh)
+static int res_get(struct em28xx_fh *fh, unsigned int bit)
 {
 	struct em28xx    *dev = fh->dev;
-	int		 rc   = 0;
 
-	/* This instance already has stream_on */
-	if (fh->stream_on)
-		return rc;
+	if (fh->resources & bit)
+		/* have it already allocated */
+		return 1;
 
-	if (dev->stream_on)
-		return -EBUSY;
+	/* is it free? */
+	mutex_lock(&dev->lock);
+	if (dev->resources & bit) {
+		/* no, someone else uses it */
+		mutex_unlock(&dev->lock);
+		return 0;
+	}
+	/* it's free, grab it */
+	fh->resources  |= bit;
+	dev->resources |= bit;
+	em28xx_videodbg("res: get %d\n", bit);
+	mutex_unlock(&dev->lock);
+	return 1;
+}
 
-	dev->stream_on = 1;
-	fh->stream_on  = 1;
-	return rc;
+static int res_check(struct em28xx_fh *fh, unsigned int bit)
+{
+	return (fh->resources & bit);
 }
 
-static int res_check(struct em28xx_fh *fh)
+static int res_locked(struct em28xx *dev, unsigned int bit)
 {
-	return fh->stream_on;
+	return (dev->resources & bit);
 }
 
-static void res_free(struct em28xx_fh *fh)
+static void res_free(struct em28xx_fh *fh, unsigned int bits)
 {
 	struct em28xx    *dev = fh->dev;
 
-	fh->stream_on = 0;
-	dev->stream_on = 0;
+	BUG_ON((fh->resources & bits) != bits);
+
+	mutex_lock(&dev->lock);
+	fh->resources  &= ~bits;
+	dev->resources &= ~bits;
+	em28xx_videodbg("res: put %d\n", bits);
+	mutex_unlock(&dev->lock);
+}
+
+static int get_ressource(struct em28xx_fh *fh)
+{
+	switch (fh->type) {
+	case V4L2_BUF_TYPE_VIDEO_CAPTURE:
+		return EM28XX_RESOURCE_VIDEO;
+	case V4L2_BUF_TYPE_VBI_CAPTURE:
+		return EM28XX_RESOURCE_VBI;
+	default:
+		BUG();
+		return 0;
+	}
 }
 
 /*
@@ -1103,12 +1132,6 @@ static int vidioc_s_fmt_vid_cap(struct file *file, void *priv,
 		goto out;
 	}
 
-	if (dev->stream_on && !fh->stream_on) {
-		em28xx_errdev("%s device in use by another fh\n", __func__);
-		rc = -EBUSY;
-		goto out;
-	}
-
 	rc = em28xx_set_video_format(dev, f->fmt.pix.pixelformat,
 				f->fmt.pix.width, f->fmt.pix.height);
 
@@ -1668,24 +1691,25 @@ static int vidioc_streamon(struct file *file, void *priv,
 {
 	struct em28xx_fh      *fh  = priv;
 	struct em28xx         *dev = fh->dev;
-	int                   rc;
+	int                   rc = -EINVAL;
 
 	rc = check_dev(dev);
 	if (rc < 0)
 		return rc;
 
+	if (unlikely(type != fh->type))
+		return -EINVAL;
 
-	mutex_lock(&dev->lock);
-	rc = res_get(fh);
+	em28xx_videodbg("vidioc_streamon fh=%p t=%d fh->res=%d dev->res=%d\n",
+			fh, type, fh->resources, dev->resources);
 
-	if (likely(rc >= 0)) {
-		if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
-			rc = videobuf_streamon(&fh->vb_vidq);
-		else if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE)
-			rc = videobuf_streamon(&fh->vb_vbiq);
-	}
+	if (unlikely(!res_get(fh,get_ressource(fh))))
+		return -EBUSY;
 
-	mutex_unlock(&dev->lock);
+	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
+		rc = videobuf_streamon(&fh->vb_vidq);
+	else if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE)
+		rc = videobuf_streamon(&fh->vb_vbiq);
 
 	return rc;
 }
@@ -1707,16 +1731,16 @@ static int vidioc_streamoff(struct file *file, void *priv,
 	if (type != fh->type)
 		return -EINVAL;
 
-	mutex_lock(&dev->lock);
+	em28xx_videodbg("vidioc_streamoff fh=%p t=%d fh->res=%d dev->res=%d\n",
+			fh, type, fh->resources, dev->resources);
 
-	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
+	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
 		videobuf_streamoff(&fh->vb_vidq);
-	else if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE)
+		res_free(fh, EM28XX_RESOURCE_VIDEO);
+	} else if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE) {
 		videobuf_streamoff(&fh->vb_vbiq);
-
-	res_free(fh);
-
-	mutex_unlock(&dev->lock);
+		res_free(fh, EM28XX_RESOURCE_VBI);
+	}
 
 	return 0;
 }
@@ -2095,17 +2119,16 @@ static int em28xx_v4l2_open(struct file *filp)
 	else
 		field = V4L2_FIELD_INTERLACED;
 
-	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
-		videobuf_queue_vmalloc_init(&fh->vb_vidq, &em28xx_video_qops,
-					    NULL, &dev->slock, fh->type, field,
-					    sizeof(struct em28xx_buffer), fh);
+	videobuf_queue_vmalloc_init(&fh->vb_vidq, &em28xx_video_qops,
+				    NULL, &dev->slock,
+				    V4L2_BUF_TYPE_VIDEO_CAPTURE, field,
+				    sizeof(struct em28xx_buffer), fh);
 
-	if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE)
-		videobuf_queue_vmalloc_init(&fh->vb_vbiq, &em28xx_vbi_qops,
-					    NULL, &dev->slock,
-					    V4L2_BUF_TYPE_VBI_CAPTURE,
-					    V4L2_FIELD_SEQ_TB,
-					    sizeof(struct em28xx_buffer), fh);
+	videobuf_queue_vmalloc_init(&fh->vb_vbiq, &em28xx_vbi_qops,
+				    NULL, &dev->slock,
+				    V4L2_BUF_TYPE_VBI_CAPTURE,
+				    V4L2_FIELD_SEQ_TB,
+				    sizeof(struct em28xx_buffer), fh);
 
 	mutex_unlock(&dev->lock);
 
@@ -2162,20 +2185,21 @@ static int em28xx_v4l2_close(struct file *filp)
 
 	em28xx_videodbg("users=%d\n", dev->users);
 
-
-	mutex_lock(&dev->lock);
-	if (res_check(fh))
-		res_free(fh);
-
-	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE && dev->users == 1) {
+	if (res_check(fh, EM28XX_RESOURCE_VIDEO)) {
 		videobuf_stop(&fh->vb_vidq);
-		videobuf_mmap_free(&fh->vb_vidq);
+		res_free(fh, EM28XX_RESOURCE_VIDEO);
+	}
 
+	if (res_check(fh, EM28XX_RESOURCE_VBI)) {
+		videobuf_stop(&fh->vb_vbiq);
+		res_free(fh, EM28XX_RESOURCE_VBI);
+	}
+
+	if(dev->users == 1) {
 		/* the device is already disconnect,
 		   free the remaining resources */
 		if (dev->state & DEV_DISCONNECTED) {
 			em28xx_release_resources(dev);
-			mutex_unlock(&dev->lock);
 			kfree(dev);
 			return 0;
 		}
@@ -2197,15 +2221,11 @@ static int em28xx_v4l2_close(struct file *filp)
 		}
 	}
 
-	if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE) {
-		videobuf_stop(&fh->vb_vbiq);
-		videobuf_mmap_free(&fh->vb_vbiq);
-	}
-
+	videobuf_mmap_free(&fh->vb_vidq);
+	videobuf_mmap_free(&fh->vb_vbiq);
 	kfree(fh);
 	dev->users--;
 	wake_up_interruptible_nr(&dev->open, 1);
-	mutex_unlock(&dev->lock);
 	return 0;
 }
 
@@ -2230,12 +2250,8 @@ em28xx_v4l2_read(struct file *filp, char __user *buf, size_t count,
 	 */
 
 	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
-		mutex_lock(&dev->lock);
-		rc = res_get(fh);
-		mutex_unlock(&dev->lock);
-
-		if (unlikely(rc < 0))
-			return rc;
+		if (res_locked(dev, EM28XX_RESOURCE_VIDEO))
+			return -EBUSY;
 
 		return videobuf_read_stream(&fh->vb_vidq, buf, count, pos, 0,
 					filp->f_flags & O_NONBLOCK);
@@ -2243,9 +2259,8 @@ em28xx_v4l2_read(struct file *filp, char __user *buf, size_t count,
 
 
 	if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE) {
-		mutex_lock(&dev->lock);
-		rc = res_get(fh);
-		mutex_unlock(&dev->lock);
+		if (!res_get(fh, EM28XX_RESOURCE_VBI))
+			return -EBUSY;
 
 		return videobuf_read_stream(&fh->vb_vbiq, buf, count, pos, 0,
 					filp->f_flags & O_NONBLOCK);
@@ -2268,19 +2283,17 @@ static unsigned int em28xx_v4l2_poll(struct file *filp, poll_table *wait)
 	if (rc < 0)
 		return rc;
 
-	mutex_lock(&dev->lock);
-	rc = res_get(fh);
-	mutex_unlock(&dev->lock);
-
-	if (unlikely(rc < 0))
-		return POLLERR;
-
-	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
+	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE) {
+		if (!res_get(fh, EM28XX_RESOURCE_VIDEO))
+			return POLLERR;
 		return videobuf_poll_stream(filp, &fh->vb_vidq, wait);
-	else if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE)
+	} else if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE) {
+		if (!res_get(fh, EM28XX_RESOURCE_VBI))
+			return POLLERR;
 		return videobuf_poll_stream(filp, &fh->vb_vbiq, wait);
-	else
+	} else {
 		return POLLERR;
+	}
 }
 
 /*
@@ -2296,13 +2309,6 @@ static int em28xx_v4l2_mmap(struct file *filp, struct vm_area_struct *vma)
 	if (rc < 0)
 		return rc;
 
-	mutex_lock(&dev->lock);
-	rc = res_get(fh);
-	mutex_unlock(&dev->lock);
-
-	if (unlikely(rc < 0))
-		return rc;
-
 	if (fh->type == V4L2_BUF_TYPE_VIDEO_CAPTURE)
 		rc = videobuf_mmap_mapper(&fh->vb_vidq, vma);
 	else if (fh->type == V4L2_BUF_TYPE_VBI_CAPTURE)