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[PATCH] backlight: fix oops in __mutex_lock_slowpath during head /sys/class/graphics/fb0/*

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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>
This commit is contained in:
Michael Hanselmann 2006-09-25 16:25:07 -07:00 committed by Linus Torvalds
parent f3ef9ead31
commit 25981de5b8
1 changed files with 12 additions and 0 deletions
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12
drivers/video/fbsysfs.c
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@ -397,6 +397,12 @@ static ssize_t store_bl_curve(struct class_device *class_device,
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 @@ static ssize_t show_bl_curve(struct class_device *class_device, char *buf)
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,