[PATCH] backlight: fix oops in __mutex_lock_slowpath during head /sys/class/graphics/fb0/*
Seems like not all drivers use the framebuffer_alloc() function and won't
have an initialized mutex. But those don't have a backlight, anyway.
Signed-off-by: Michael Hanselmann <linux-kernel@hansmi.ch>
Cc: Olaf Hering <olaf@aepfle.de>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Cc: Daniel R Thompson <daniel.thompson@st.com>
Cc: Jon Smirl <jonsmirl@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/drivers/video/fbsysfs.c b/drivers/video/fbsysfs.c
index 4f78f23..c151dcf 100644
--- a/drivers/video/fbsysfs.c
+++ b/drivers/video/fbsysfs.c
@@ -397,6 +397,12 @@
u8 tmp_curve[FB_BACKLIGHT_LEVELS];
unsigned int i;
+ /* Some drivers don't use framebuffer_alloc(), but those also
+ * don't have backlights.
+ */
+ if (!fb_info || !fb_info->bl_dev)
+ return -ENODEV;
+
if (count != (FB_BACKLIGHT_LEVELS / 8 * 24))
return -EINVAL;
@@ -430,6 +436,12 @@
ssize_t len = 0;
unsigned int i;
+ /* Some drivers don't use framebuffer_alloc(), but those also
+ * don't have backlights.
+ */
+ if (!fb_info || !fb_info->bl_dev)
+ return -ENODEV;
+
mutex_lock(&fb_info->bl_mutex);
for (i = 0; i < FB_BACKLIGHT_LEVELS; i += 8)
len += snprintf(&buf[len], PAGE_SIZE,