[media] gspca: Update / fix various comments wrt workqueue usb_lock usage

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

drivers/media/usb/gspca/finepix.c

@@ -77,7 +77,14 @@ static int command(struct gspca_dev *gspca_dev,
 			12, FPIX_TIMEOUT);
 }
 
-/* workqueue */
+/*
+ * This function is called as a workqueue function and runs whenever the camera
+ * is streaming data. Because it is a workqueue function it is allowed to sleep
+ * so we can use synchronous USB calls. To avoid possible collisions with other
+ * threads attempting to use gspca_dev->usb_buf we take the usb_lock when
+ * performing USB operations using it. In practice we don't really need this
+ * as the camera doesn't provide any controls.
+ */
 static void dostream(struct work_struct *work)
 {
 	struct usb_fpix *dev = container_of(work, struct usb_fpix, work_struct);

drivers/media/usb/gspca/jl2005bcd.c

@@ -306,15 +306,13 @@ static int jl2005c_stop(struct gspca_dev *gspca_dev)
 	return retval;
 }
 
-/* This function is called as a workqueue function and runs whenever the camera
+/*
+ * This function is called as a workqueue function and runs whenever the camera
  * is streaming data. Because it is a workqueue function it is allowed to sleep
  * so we can use synchronous USB calls. To avoid possible collisions with other
- * threads attempting to use the camera's USB interface the gspca usb_lock is
- * used when performing the one USB control operation inside the workqueue,
- * which tells the camera to close the stream. In practice the only thing
- * which needs to be protected against is the usb_set_interface call that
- * gspca makes during stream_off. Otherwise the camera doesn't provide any
- * controls that the user could try to change.
+ * threads attempting to use gspca_dev->usb_buf we take the usb_lock when
+ * performing USB operations using it. In practice we don't really need this
+ * as the camera doesn't provide any controls.
  */
 static void jl2005c_dostream(struct work_struct *work)
 {

drivers/media/usb/gspca/sn9c20x.c

@@ -2197,8 +2197,10 @@ static void qual_upd(struct work_struct *work)
 	struct gspca_dev *gspca_dev = &sd->gspca_dev;
 	s32 qual = v4l2_ctrl_g_ctrl(sd->jpegqual);
 
+	/* To protect gspca_dev->usb_buf and gspca_dev->usb_err */
 	mutex_lock(&gspca_dev->usb_lock);
 	PDEBUG(D_STREAM, "qual_upd %d%%", qual);
+	gspca_dev->usb_err = 0;
 	set_quality(gspca_dev, qual);
 	mutex_unlock(&gspca_dev->usb_lock);
 }

drivers/media/usb/gspca/sonixj.c

@@ -2380,8 +2380,10 @@ static void qual_upd(struct work_struct *work)
 	struct sd *sd = container_of(work, struct sd, work);
 	struct gspca_dev *gspca_dev = &sd->gspca_dev;
 
+	/* To protect gspca_dev->usb_buf and gspca_dev->usb_err */
 	mutex_lock(&gspca_dev->usb_lock);
 	PDEBUG(D_STREAM, "qual_upd %d%%", sd->quality);
+	gspca_dev->usb_err = 0;
 	setjpegqual(gspca_dev);
 	mutex_unlock(&gspca_dev->usb_lock);
 }

drivers/media/usb/gspca/sq905.c

@@ -201,14 +201,13 @@ sq905_read_data(struct gspca_dev *gspca_dev, u8 *data, int size, int need_lock)
 	return 0;
 }
 
-/* This function is called as a workqueue function and runs whenever the camera
+/*
+ * This function is called as a workqueue function and runs whenever the camera
  * is streaming data. Because it is a workqueue function it is allowed to sleep
  * so we can use synchronous USB calls. To avoid possible collisions with other
- * threads attempting to use the camera's USB interface we take the gspca
- * usb_lock when performing USB operations. In practice the only thing we need
- * to protect against is the usb_set_interface call that gspca makes during
- * stream_off as the camera doesn't provide any controls that the user could try
- * to change.
+ * threads attempting to use gspca_dev->usb_buf we take the usb_lock when
+ * performing USB operations using it. In practice we don't really need this
+ * as the camera doesn't provide any controls.
  */
 static void sq905_dostream(struct work_struct *work)
 {

drivers/media/usb/gspca/sq905c.c

@@ -123,15 +123,13 @@ static int sq905c_read(struct gspca_dev *gspca_dev, u16 command, u16 index,
 	return 0;
 }
 
-/* This function is called as a workqueue function and runs whenever the camera
+/*
+ * This function is called as a workqueue function and runs whenever the camera
  * is streaming data. Because it is a workqueue function it is allowed to sleep
  * so we can use synchronous USB calls. To avoid possible collisions with other
- * threads attempting to use the camera's USB interface the gspca usb_lock is
- * used when performing the one USB control operation inside the workqueue,
- * which tells the camera to close the stream. In practice the only thing
- * which needs to be protected against is the usb_set_interface call that
- * gspca makes during stream_off. Otherwise the camera doesn't provide any
- * controls that the user could try to change.
+ * threads attempting to use gspca_dev->usb_buf we take the usb_lock when
+ * performing USB operations using it. In practice we don't really need this
+ * as the camera doesn't provide any controls.
  */
 static void sq905c_dostream(struct work_struct *work)
 {

drivers/media/usb/gspca/vicam.c

@@ -110,7 +110,7 @@ static int vicam_set_camera_power(struct gspca_dev *gspca_dev, int state)
 }
 
 /*
- *  request and read a block of data - see warning on vicam_command.
+ *  request and read a block of data
  */
 static int vicam_read_frame(struct gspca_dev *gspca_dev, u8 *data, int size)
 {
@@ -170,14 +170,13 @@ static int vicam_read_frame(struct gspca_dev *gspca_dev, u8 *data, int size)
 	return 0;
 }
 
-/* This function is called as a workqueue function and runs whenever the camera
+/*
+ * This function is called as a workqueue function and runs whenever the camera
  * is streaming data. Because it is a workqueue function it is allowed to sleep
  * so we can use synchronous USB calls. To avoid possible collisions with other
- * threads attempting to use the camera's USB interface we take the gspca
- * usb_lock when performing USB operations. In practice the only thing we need
- * to protect against is the usb_set_interface call that gspca makes during
- * stream_off as the camera doesn't provide any controls that the user could try
- * to change.
+ * threads attempting to use gspca_dev->usb_buf we take the usb_lock when
+ * performing USB operations using it. In practice we don't really need this
+ * as the cameras controls are only written from the workqueue.
  */
 static void vicam_dostream(struct work_struct *work)
 {

drivers/media/usb/gspca/zc3xx.c

@@ -5945,6 +5945,7 @@ static void transfer_update(struct work_struct *work)
 	for (;;) {
 		msleep(100);
 
+		/* To protect gspca_dev->usb_buf and gspca_dev->usb_err */
 		mutex_lock(&gspca_dev->usb_lock);
 #ifdef CONFIG_PM
 		if (gspca_dev->frozen)
@@ -6831,7 +6832,8 @@ static int sd_start(struct gspca_dev *gspca_dev)
 	return 0;
 }
 
-/* called on streamoff with alt 0 and on disconnect */
+/* called on streamoff with alt==0 and on disconnect */
+/* the usb_lock is held at entry - restore on exit */
 static void sd_stop0(struct gspca_dev *gspca_dev)
 {
 	struct sd *sd = (struct sd *) gspca_dev;