There is a small window during probing when IO is running
but the backlight is not registered. Processing events
during that time will crash. The completion handler
needs to check for a backlight before scheduling work.
The bug is as old as the driver.
Signed-off-by: Oliver Neukum <oneukum@xxxxxxxx>
CC: stable@xxxxxxxxxxxxxxx
---
drivers/usb/misc/appledisplay.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/misc/appledisplay.c b/drivers/usb/misc/appledisplay.c
index c8098e9b432e..62b5a30edc42 100644
--- a/drivers/usb/misc/appledisplay.c
+++ b/drivers/usb/misc/appledisplay.c
@@ -107,7 +107,12 @@ static void appledisplay_complete(struct urb *urb)
case ACD_BTN_BRIGHT_UP:
case ACD_BTN_BRIGHT_DOWN:
pdata->button_pressed = 1;
- schedule_delayed_work(&pdata->work, 0);
+ /*
+ * there is a window during which no device
+ * is registered
+ */
+ if (pdata->bd )
+ schedule_delayed_work(&pdata->work, 0);
break;
case ACD_BTN_NONE:
default:
@@ -202,6 +207,7 @@ static int appledisplay_probe(struct usb_interface *iface,
const struct usb_device_id *id)
{
struct backlight_properties props;
+ struct backlight_device *backlight;
struct appledisplay *pdata;
struct usb_device *udev = interface_to_usbdev(iface);
struct usb_endpoint_descriptor *endpoint;
@@ -272,13 +278,14 @@ static int appledisplay_probe(struct usb_interface *iface,
memset(&props, 0, sizeof(struct backlight_properties));
props.type = BACKLIGHT_RAW;
props.max_brightness = 0xff;
- pdata->bd = backlight_device_register(bl_name, NULL, pdata,
+ backlight = backlight_device_register(bl_name, NULL, pdata,
&appledisplay_bl_data, &props);
- if (IS_ERR(pdata->bd)) {
+ if (IS_ERR(backlight)) {
dev_err(&iface->dev, "Backlight registration failed\n");
- retval = PTR_ERR(pdata->bd);
+ retval = PTR_ERR(backlight);
goto error;
}
+ pdata->bd = backlight;
/* Try to get brightness */
brightness = appledisplay_bl_get_brightness(pdata->bd);
--
2.45.2
