[media] gspca: Don't set gspca_dev->dev to NULL before stop0

In commit a3d6e8cc0e gspca_dev->dev is set
to NULL on disconnect, before calling stop0. The plan was to get rid of
gspca_dev->present and instead simply check for gspca_dev->dev everywhere
where we were checking for present. This should be race free since all users
of gspca_dev->dev hold the usb_lock, or so I thought.

But I was wrong, drivers which use a work-queue + synchronous bulk transfers
to get the video data don't hold the usb_lock while doing so, their stop0
callbacks stop the workqueue, so they won't be using gspca_dev->dev anymore
after the stop0 call, but they might be dereferincing it before, so we should
not set gspca_dev->dev to NULL on disconnect before calling stop0.

This also means that the workqueue functions in these drivers cannot
use gspca_dev->dev to check if they need to stop because of disconnection,
so we will need to keep gspca_dev->present around, and set that to 0 on
disconnect, before calling stop0. Unfortunately as part of the plan to remove
gspca_dev->present, these workqueues where already moved over to checking
for gspca_dev->dev instead of gspca_dev->present as part of commit
254902b01d, so this patch also reverts those
parts of that commit.

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

drivers/media/usb/gspca/finepix.c

@@ -94,7 +94,7 @@ static void dostream(struct work_struct *work)
 
 	/* loop reading a frame */
 again:
-	while (gspca_dev->dev && gspca_dev->streaming) {
+	while (gspca_dev->present && gspca_dev->streaming) {
 #ifdef CONFIG_PM
 		if (gspca_dev->frozen)
 			break;
@@ -110,7 +110,7 @@ again:
 		if (gspca_dev->frozen)
 			break;
 #endif
-		if (!gspca_dev->dev || !gspca_dev->streaming)
+		if (!gspca_dev->present || !gspca_dev->streaming)
 			break;
 
 		/* the frame comes in parts */
@@ -129,7 +129,7 @@ again:
 			if (gspca_dev->frozen)
 				goto out;
 #endif
-			if (!gspca_dev->dev || !gspca_dev->streaming)
+			if (!gspca_dev->present || !gspca_dev->streaming)
 				goto out;
 			if (len < FPIX_MAX_TRANSFER ||
 				(data[len - 2] == 0xff &&

drivers/media/usb/gspca/gspca.c

@@ -2358,8 +2358,6 @@ void gspca_disconnect(struct usb_interface *intf)
 
 	mutex_lock(&gspca_dev->usb_lock);
 
-	usb_set_intfdata(intf, NULL);
-	gspca_dev->dev = NULL;
 	gspca_dev->present = 0;
 	destroy_urbs(gspca_dev);
 
@@ -2375,6 +2373,7 @@ void gspca_disconnect(struct usb_interface *intf)
 	if (gspca_dev->sd_desc->stop0 && gspca_dev->streaming)
 		gspca_dev->sd_desc->stop0(gspca_dev);
 	gspca_dev->streaming = 0;
+	gspca_dev->dev = NULL;
 	wake_up_interruptible(&gspca_dev->wq);
 
 	v4l2_device_disconnect(&gspca_dev->v4l2_dev);

drivers/media/usb/gspca/jl2005bcd.c

@@ -335,7 +335,7 @@ static void jl2005c_dostream(struct work_struct *work)
 		goto quit_stream;
 	}
 
-	while (gspca_dev->dev && gspca_dev->streaming) {
+	while (gspca_dev->present && gspca_dev->streaming) {
 #ifdef CONFIG_PM
 		if (gspca_dev->frozen)
 			break;
@@ -371,7 +371,7 @@ static void jl2005c_dostream(struct work_struct *work)
 					buffer, act_len);
 			header_read = 1;
 		}
-		while (bytes_left > 0 && gspca_dev->dev) {
+		while (bytes_left > 0 && gspca_dev->present) {
 			data_len = bytes_left > JL2005C_MAX_TRANSFER ?
 				JL2005C_MAX_TRANSFER : bytes_left;
 			ret = usb_bulk_msg(gspca_dev->dev,
@@ -394,7 +394,7 @@ static void jl2005c_dostream(struct work_struct *work)
 		}
 	}
 quit_stream:
-	if (gspca_dev->dev) {
+	if (gspca_dev->present) {
 		mutex_lock(&gspca_dev->usb_lock);
 		jl2005c_stop(gspca_dev);
 		mutex_unlock(&gspca_dev->usb_lock);

drivers/media/usb/gspca/sq905.c

@@ -232,7 +232,7 @@ static void sq905_dostream(struct work_struct *work)
 	frame_sz = gspca_dev->cam.cam_mode[gspca_dev->curr_mode].sizeimage
 			+ FRAME_HEADER_LEN;
 
-	while (gspca_dev->dev && gspca_dev->streaming) {
+	while (gspca_dev->present && gspca_dev->streaming) {
 #ifdef CONFIG_PM
 		if (gspca_dev->frozen)
 			break;
@@ -246,7 +246,7 @@ static void sq905_dostream(struct work_struct *work)
 		   we must finish reading an entire frame, otherwise the
 		   next time we stream we start reading in the middle of a
 		   frame. */
-		while (bytes_left > 0 && gspca_dev->dev) {
+		while (bytes_left > 0 && gspca_dev->present) {
 			data_len = bytes_left > SQ905_MAX_TRANSFER ?
 				SQ905_MAX_TRANSFER : bytes_left;
 			ret = sq905_read_data(gspca_dev, buffer, data_len, 1);
@@ -278,7 +278,7 @@ static void sq905_dostream(struct work_struct *work)
 				gspca_frame_add(gspca_dev, LAST_PACKET,
 						NULL, 0);
 		}
-		if (gspca_dev->dev) {
+		if (gspca_dev->present) {
 			/* acknowledge the frame */
 			mutex_lock(&gspca_dev->usb_lock);
 			ret = sq905_ack_frame(gspca_dev);
@@ -288,7 +288,7 @@ static void sq905_dostream(struct work_struct *work)
 		}
 	}
 quit_stream:
-	if (gspca_dev->dev) {
+	if (gspca_dev->present) {
 		mutex_lock(&gspca_dev->usb_lock);
 		sq905_command(gspca_dev, SQ905_CLEAR);
 		mutex_unlock(&gspca_dev->usb_lock);

drivers/media/usb/gspca/sq905c.c

@@ -150,7 +150,7 @@ static void sq905c_dostream(struct work_struct *work)
 		goto quit_stream;
 	}
 
-	while (gspca_dev->dev && gspca_dev->streaming) {
+	while (gspca_dev->present && gspca_dev->streaming) {
 #ifdef CONFIG_PM
 		if (gspca_dev->frozen)
 			break;
@@ -173,7 +173,7 @@ static void sq905c_dostream(struct work_struct *work)
 		packet_type = FIRST_PACKET;
 		gspca_frame_add(gspca_dev, packet_type,
 				buffer, FRAME_HEADER_LEN);
-		while (bytes_left > 0 && gspca_dev->dev) {
+		while (bytes_left > 0 && gspca_dev->present) {
 			data_len = bytes_left > SQ905C_MAX_TRANSFER ?
 				SQ905C_MAX_TRANSFER : bytes_left;
 			ret = usb_bulk_msg(gspca_dev->dev,
@@ -195,7 +195,7 @@ static void sq905c_dostream(struct work_struct *work)
 		}
 	}
 quit_stream:
-	if (gspca_dev->dev) {
+	if (gspca_dev->present) {
 		mutex_lock(&gspca_dev->usb_lock);
 		sq905c_command(gspca_dev, SQ905C_CLEAR, 0);
 		mutex_unlock(&gspca_dev->usb_lock);

drivers/media/usb/gspca/vicam.c

@@ -194,7 +194,7 @@ static void vicam_dostream(struct work_struct *work)
 		goto exit;
 	}
 
-	while (gspca_dev->dev && gspca_dev->streaming) {
+	while (gspca_dev->present && gspca_dev->streaming) {
 #ifdef CONFIG_PM
 		if (gspca_dev->frozen)
 			break;
@@ -299,7 +299,7 @@ static void sd_stop0(struct gspca_dev *gspca_dev)
 	dev->work_thread = NULL;
 	mutex_lock(&gspca_dev->usb_lock);
 
-	if (gspca_dev->dev)
+	if (gspca_dev->present)
 		vicam_set_camera_power(gspca_dev, 0);
 }
 

drivers/media/usb/gspca/xirlink_cit.c

@@ -2697,9 +2697,7 @@ static void sd_stop0(struct gspca_dev *gspca_dev)
 {
 	struct sd *sd = (struct sd *) gspca_dev;
 
-	/* We cannot use gspca_dev->present here as that is not set when
-	   sd_init gets called and we get called from sd_init */
-	if (!gspca_dev->dev)
+	if (!gspca_dev->present)
 		return;
 
 	switch (sd->model) {

drivers/media/usb/gspca/zc3xx.c

@@ -5950,7 +5950,7 @@ static void transfer_update(struct work_struct *work)
 		if (gspca_dev->frozen)
 			goto err;
 #endif
-		if (!gspca_dev->dev || !gspca_dev->streaming)
+		if (!gspca_dev->present || !gspca_dev->streaming)
 			goto err;
 
 		/* Bit 0 of register 11 indicates FIFO overflow */
@@ -6842,7 +6842,7 @@ static void sd_stop0(struct gspca_dev *gspca_dev)
 		mutex_lock(&gspca_dev->usb_lock);
 		sd->work_thread = NULL;
 	}
-	if (!gspca_dev->dev)
+	if (!gspca_dev->present)
 		return;
 	send_unknown(gspca_dev, sd->sensor);
 }