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

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)

drivers/media/video/em28xx/em28xx.h

@@ -444,6 +444,10 @@ enum em28xx_dev_state {
 #define EM28XX_AUDIO   0x10
 #define EM28XX_DVB     0x20
 
+/* em28xx resource types (used for res_get/res_lock etc */
+#define EM28XX_RESOURCE_VIDEO 0x01
+#define EM28XX_RESOURCE_VBI   0x02
+
 struct em28xx_audio {
 	char name[50];
 	char *transfer_buffer[EM28XX_AUDIO_BUFS];
@@ -464,8 +468,8 @@ struct em28xx;
 
 struct em28xx_fh {
 	struct em28xx *dev;
-	unsigned int  stream_on:1;	/* Locks streams */
 	int           radio;
+	unsigned int  resources;
 
 	struct videobuf_queue        vb_vidq;
 	struct videobuf_queue        vb_vbiq;
@@ -495,7 +499,6 @@ struct em28xx {
 	/* Vinmode/Vinctl used at the driver */
 	int vinmode, vinctl;
 
-	unsigned int stream_on:1;	/* Locks streams */
 	unsigned int has_audio_class:1;
 	unsigned int has_alsa_audio:1;
 
@@ -563,6 +566,9 @@ struct em28xx {
 	struct video_device *vbi_dev;
 	struct video_device *radio_dev;
 
+	/* resources in use */
+	unsigned int resources;
+
 	unsigned char eedata[256];
 
 	/* Isoc control struct */