[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>
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@ -397,6 +397,12 @@ static ssize_t store_bl_curve(struct class_device *class_device,
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u8 tmp_curve[FB_BACKLIGHT_LEVELS];
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unsigned int i;
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/* Some drivers don't use framebuffer_alloc(), but those also
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* don't have backlights.
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*/
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if (!fb_info || !fb_info->bl_dev)
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return -ENODEV;
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if (count != (FB_BACKLIGHT_LEVELS / 8 * 24))
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return -EINVAL;
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@ -430,6 +436,12 @@ static ssize_t show_bl_curve(struct class_device *class_device, char *buf)
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ssize_t len = 0;
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unsigned int i;
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/* Some drivers don't use framebuffer_alloc(), but those also
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* don't have backlights.
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*/
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if (!fb_info || !fb_info->bl_dev)
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return -ENODEV;
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mutex_lock(&fb_info->bl_mutex);
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for (i = 0; i < FB_BACKLIGHT_LEVELS; i += 8)
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len += snprintf(&buf[len], PAGE_SIZE,
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