[media] pwc: Allow dqbuf / read to complete while waiting for controls

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

3 files changed, 38 insertions, 4 deletions

diff --git a/drivers/media/video/pwc/pwc-if.c b/drivers/media/video/pwc/pwc-if.c
index 1d5a6db915fa..fdf113fe51c3 100644
--- a/drivers/media/video/pwc/pwc-if.c
+++ b/drivers/media/video/pwc/pwc-if.c
@@ -1160,6 +1160,7 @@ static int usb_pwc_probe(struct usb_interface *intf, const struct usb_device_id
         pwc_construct(pdev); /* set min/max sizes correct */
 
         mutex_init(&pdev->modlock);
+        mutex_init(&pdev->udevlock);
         spin_lock_init(&pdev->queued_bufs_lock);
         INIT_LIST_HEAD(&pdev->queued_bufs);
 
@@ -1297,6 +1298,7 @@ static void usb_pwc_disconnect(struct usb_interface *intf)
 {
         struct pwc_device *pdev  = usb_get_intfdata(intf);
 
+        mutex_lock(&pdev->udevlock);
         mutex_lock(&pdev->modlock);
 
         usb_set_intfdata(intf, NULL);
@@ -1306,6 +1308,7 @@ static void usb_pwc_disconnect(struct usb_interface *intf)
         pdev->udev = NULL;
 
         mutex_unlock(&pdev->modlock);
+        mutex_unlock(&pdev->udevlock);
 
         pwc_remove_sysfs_files(pdev);
         video_unregister_device(&pdev->vdev);
diff --git a/drivers/media/video/pwc/pwc-v4l.c b/drivers/media/video/pwc/pwc-v4l.c
index 986dd5d6187a..537657283e79 100644
--- a/drivers/media/video/pwc/pwc-v4l.c
+++ b/drivers/media/video/pwc/pwc-v4l.c
@@ -526,8 +526,24 @@ static int pwc_g_volatile_ctrl(struct v4l2_ctrl *ctrl)
                 container_of(ctrl->handler, struct pwc_device, ctrl_handler);
         int ret = 0;
 
-        if (!pdev->udev)
-                return -ENODEV;
+        /*
+         * Sometimes it can take quite long for the pwc to complete usb control
+         * transfers, so release the modlock to give streaming by another
+         * process / thread the chance to continue with a dqbuf.
+         */
+        mutex_unlock(&pdev->modlock);
+
+        /*
+         * Take the udev-lock to protect against the disconnect handler
+         * completing and setting dev->udev to NULL underneath us. Other code
+         * does not need to do this since it is protected by the modlock.
+         */
+        mutex_lock(&pdev->udevlock);
+
+        if (!pdev->udev) {
+                ret = -ENODEV;
+                goto leave;
+        }
 
         switch (ctrl->id) {
         case V4L2_CID_AUTO_WHITE_BALANCE:
@@ -590,6 +606,9 @@ static int pwc_g_volatile_ctrl(struct v4l2_ctrl *ctrl)
         if (ret)
                 PWC_ERROR("g_ctrl %s error %d\n", ctrl->name, ret);
 
+leave:
+        mutex_unlock(&pdev->udevlock);
+        mutex_lock(&pdev->modlock);
         return ret;
 }
 
@@ -751,8 +770,14 @@ static int pwc_s_ctrl(struct v4l2_ctrl *ctrl)
                 container_of(ctrl->handler, struct pwc_device, ctrl_handler);
         int ret = 0;
 
-        if (!pdev->udev)
-                return -ENODEV;
+        /* See the comments on locking in pwc_g_volatile_ctrl */
+        mutex_unlock(&pdev->modlock);
+        mutex_lock(&pdev->udevlock);
+
+        if (!pdev->udev) {
+                ret = -ENODEV;
+                goto leave;
+        }
 
         switch (ctrl->id) {
         case V4L2_CID_BRIGHTNESS:
@@ -841,6 +866,9 @@ static int pwc_s_ctrl(struct v4l2_ctrl *ctrl)
         if (ret)
                 PWC_ERROR("s_ctrl %s error %d\n", ctrl->name, ret);
 
+leave:
+        mutex_unlock(&pdev->udevlock);
+        mutex_lock(&pdev->modlock);
         return ret;
 }
 
diff --git a/drivers/media/video/pwc/pwc.h b/drivers/media/video/pwc/pwc.h
index 601a549988b5..e02dbf745155 100644
--- a/drivers/media/video/pwc/pwc.h
+++ b/drivers/media/video/pwc/pwc.h
@@ -200,6 +200,9 @@ struct pwc_device
 
         /* Pointer to our usb_device, may be NULL after unplug */
         struct usb_device *udev;
+        /* Protects the setting of udev to NULL by our disconnect handler */
+        struct mutex udevlock;
+
         /* type of cam (645, 646, 675, 680, 690, 720, 730, 740, 750) */
         int type;
         int release;            /* release number */