backlight: Fix external uses of backlight internal semaphore
backlight_device->sem has a very specific use as documented in the
header file. The external users of this are using it for a different
reason, to serialise access to the update_status() method.
backlight users were supposed to implement their own internal
serialisation of update_status() if needed but everyone is doing
things differently and incorrectly. Therefore add a global mutex to
take care of serialisation for everyone, once and for all.
Locking for get_brightness remains optional since most users don't
need it.
Also update the lcd class in a similar way.
Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index dcc6f15..35ce07b 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -107,12 +107,10 @@
if (machine_is(powermac) && pmac_backlight) {
struct backlight_properties *props;
- down(&pmac_backlight->sem);
props = pmac_backlight->props;
props->brightness = props->max_brightness;
props->power = FB_BLANK_UNBLANK;
- props->update_status(pmac_backlight);
- up(&pmac_backlight->sem);
+ backlight_update_status(pmac_backlight);
}
mutex_unlock(&pmac_backlight_mutex);
#endif
diff --git a/arch/powerpc/platforms/powermac/backlight.c b/arch/powerpc/platforms/powermac/backlight.c
index c3a8941..1be358c 100644
--- a/arch/powerpc/platforms/powermac/backlight.c
+++ b/arch/powerpc/platforms/powermac/backlight.c
@@ -37,7 +37,9 @@
*/
static atomic_t kernel_backlight_disabled = ATOMIC_INIT(0);
-/* Protect the pmac_backlight variable */
+/* Protect the pmac_backlight variable below.
+ You should hold this lock when using the pmac_backlight pointer to
+ prevent its potential removal. */
DEFINE_MUTEX(pmac_backlight_mutex);
/* Main backlight storage
@@ -49,9 +51,6 @@
* internal display, it doesn't matter. Other backlight drivers can be used
* independently.
*
- * Lock ordering:
- * pmac_backlight_mutex (global, main backlight)
- * pmac_backlight->sem (backlight class)
*/
struct backlight_device *pmac_backlight;
@@ -104,7 +103,6 @@
struct backlight_properties *props;
int brightness;
- down(&pmac_backlight->sem);
props = pmac_backlight->props;
brightness = props->brightness +
@@ -117,9 +115,7 @@
brightness = props->max_brightness;
props->brightness = brightness;
- props->update_status(pmac_backlight);
-
- up(&pmac_backlight->sem);
+ backlight_update_status(pmac_backlight);
}
mutex_unlock(&pmac_backlight_mutex);
}
@@ -145,7 +141,6 @@
if (pmac_backlight) {
struct backlight_properties *props;
- down(&pmac_backlight->sem);
props = pmac_backlight->props;
props->brightness = brightness *
(props->max_brightness + 1) /
@@ -156,8 +151,7 @@
else if (props->brightness < 0)
props->brightness = 0;
- props->update_status(pmac_backlight);
- up(&pmac_backlight->sem);
+ backlight_update_status(pmac_backlight);
error = 0;
}
@@ -196,14 +190,11 @@
if (pmac_backlight) {
struct backlight_properties *props;
- down(&pmac_backlight->sem);
props = pmac_backlight->props;
result = props->brightness *
(OLD_BACKLIGHT_MAX + 1) /
(props->max_brightness + 1);
-
- up(&pmac_backlight->sem);
}
mutex_unlock(&pmac_backlight_mutex);
diff --git a/drivers/macintosh/via-pmu-backlight.c b/drivers/macintosh/via-pmu-backlight.c
index db8bcc3..7ba2042 100644
--- a/drivers/macintosh/via-pmu-backlight.c
+++ b/drivers/macintosh/via-pmu-backlight.c
@@ -166,11 +166,9 @@
pmu_backlight_data.max_brightness / 15);
}
- down(&bd->sem);
bd->props->brightness = level;
bd->props->power = FB_BLANK_UNBLANK;
- bd->props->update_status(bd);
- up(&bd->sem);
+ backlight_update_status(bd);
mutex_lock(&pmac_backlight_mutex);
if (!pmac_backlight)
diff --git a/drivers/misc/asus-laptop.c b/drivers/misc/asus-laptop.c
index d15ee5e..7ace5b9 100644
--- a/drivers/misc/asus-laptop.c
+++ b/drivers/misc/asus-laptop.c
@@ -348,13 +348,8 @@
struct backlight_device *bd = asus_backlight_device;
if (bd) {
- down(&bd->sem);
- if (likely(bd->props)) {
- bd->props->power = blank;
- if (likely(bd->props->update_status))
- bd->props->update_status(bd);
- }
- up(&bd->sem);
+ bd->props->power = blank;
+ backlight_update_status(bd);
}
}
@@ -1028,14 +1023,9 @@
asus_backlight_device = bd;
- down(&bd->sem);
- if (likely(bd->props)) {
- bd->props->brightness = read_brightness(NULL);
- bd->props->power = FB_BLANK_UNBLANK;
- if (likely(bd->props->update_status))
- bd->props->update_status(bd);
- }
- up(&bd->sem);
+ bd->props->brightness = read_brightness(NULL);
+ bd->props->power = FB_BLANK_UNBLANK;
+ backlight_update_status(bd);
}
return 0;
}
diff --git a/drivers/usb/misc/appledisplay.c b/drivers/usb/misc/appledisplay.c
index 416cde5..cd2c557 100644
--- a/drivers/usb/misc/appledisplay.c
+++ b/drivers/usb/misc/appledisplay.c
@@ -189,11 +189,9 @@
container_of(work, struct appledisplay, work.work);
int retval;
- up(&pdata->bd->sem);
retval = appledisplay_bl_get_brightness(pdata->bd);
if (retval >= 0)
pdata->bd->props->brightness = retval;
- down(&pdata->bd->sem);
/* Poll again in about 125ms if there's still a button pressed */
if (pdata->button_pressed)
@@ -288,9 +286,7 @@
}
/* Try to get brightness */
- up(&pdata->bd->sem);
brightness = appledisplay_bl_get_brightness(pdata->bd);
- down(&pdata->bd->sem);
if (brightness < 0) {
retval = brightness;
@@ -299,9 +295,7 @@
}
/* Set brightness in backlight device */
- up(&pdata->bd->sem);
pdata->bd->props->brightness = brightness;
- down(&pdata->bd->sem);
/* save our data pointer in the interface device */
usb_set_intfdata(iface, pdata);
diff --git a/drivers/video/aty/aty128fb.c b/drivers/video/aty/aty128fb.c
index 1fa211c..5d8f73b 100644
--- a/drivers/video/aty/aty128fb.c
+++ b/drivers/video/aty/aty128fb.c
@@ -1807,10 +1807,8 @@
mutex_lock(&info->bl_mutex);
if (info->bl_dev) {
- down(&info->bl_dev->sem);
info->bl_dev->props->power = power;
__aty128_bl_update_status(info->bl_dev);
- up(&info->bl_dev->sem);
}
mutex_unlock(&info->bl_mutex);
@@ -1847,11 +1845,9 @@
219 * FB_BACKLIGHT_MAX / MAX_LEVEL);
mutex_unlock(&info->bl_mutex);
- down(&bd->sem);
bd->props->brightness = aty128_bl_data.max_brightness;
bd->props->power = FB_BLANK_UNBLANK;
- bd->props->update_status(bd);
- up(&bd->sem);
+ backlight_update_status(bd);
#ifdef CONFIG_PMAC_BACKLIGHT
mutex_lock(&pmac_backlight_mutex);
diff --git a/drivers/video/aty/atyfb_base.c b/drivers/video/aty/atyfb_base.c
index 5ea5a00..23deb35 100644
--- a/drivers/video/aty/atyfb_base.c
+++ b/drivers/video/aty/atyfb_base.c
@@ -2188,10 +2188,8 @@
mutex_lock(&info->bl_mutex);
if (info->bl_dev) {
- down(&info->bl_dev->sem);
info->bl_dev->props->power = power;
__aty_bl_update_status(info->bl_dev);
- up(&info->bl_dev->sem);
}
mutex_unlock(&info->bl_mutex);
@@ -2224,11 +2222,9 @@
0xFF * FB_BACKLIGHT_MAX / MAX_LEVEL);
mutex_unlock(&info->bl_mutex);
- down(&bd->sem);
bd->props->brightness = aty_bl_data.max_brightness;
bd->props->power = FB_BLANK_UNBLANK;
- bd->props->update_status(bd);
- up(&bd->sem);
+ backlight_update_status(bd);
#ifdef CONFIG_PMAC_BACKLIGHT
mutex_lock(&pmac_backlight_mutex);
diff --git a/drivers/video/aty/radeon_backlight.c b/drivers/video/aty/radeon_backlight.c
index 8b66df6..9cfceca 100644
--- a/drivers/video/aty/radeon_backlight.c
+++ b/drivers/video/aty/radeon_backlight.c
@@ -194,11 +194,9 @@
217 * FB_BACKLIGHT_MAX / MAX_RADEON_LEVEL);
mutex_unlock(&rinfo->info->bl_mutex);
- down(&bd->sem);
bd->props->brightness = radeon_bl_data.max_brightness;
bd->props->power = FB_BLANK_UNBLANK;
- bd->props->update_status(bd);
- up(&bd->sem);
+ backlight_update_status(bd);
#ifdef CONFIG_PMAC_BACKLIGHT
mutex_lock(&pmac_backlight_mutex);
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 7a85be4..347081d 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -37,8 +37,7 @@
if (!bd->props->check_fb ||
bd->props->check_fb(evdata->info)) {
bd->props->fb_blank = *(int *)evdata->data;
- if (bd->props && bd->props->update_status)
- bd->props->update_status(bd);
+ backlight_update_status(bd);
}
up(&bd->sem);
return 0;
@@ -97,8 +96,7 @@
if (bd->props) {
pr_debug("backlight: set power to %d\n", power);
bd->props->power = power;
- if (bd->props->update_status)
- bd->props->update_status(bd);
+ backlight_update_status(bd);
rc = count;
}
up(&bd->sem);
@@ -140,8 +138,7 @@
pr_debug("backlight: set brightness to %d\n",
brightness);
bd->props->brightness = brightness;
- if (bd->props->update_status)
- bd->props->update_status(bd);
+ backlight_update_status(bd);
rc = count;
}
}
@@ -230,6 +227,7 @@
if (!new_bd)
return ERR_PTR(-ENOMEM);
+ mutex_init(&new_bd->update_lock);
init_MUTEX(&new_bd->sem);
new_bd->props = bp;
memset(&new_bd->class_dev, 0, sizeof(new_bd->class_dev));
diff --git a/drivers/video/backlight/lcd.c b/drivers/video/backlight/lcd.c
index 9590248..1e1e61a 100644
--- a/drivers/video/backlight/lcd.c
+++ b/drivers/video/backlight/lcd.c
@@ -198,6 +198,7 @@
return ERR_PTR(-ENOMEM);
init_MUTEX(&new_ld->sem);
+ mutex_init(&new_ld->update_lock);
new_ld->props = lp;
memset(&new_ld->class_dev, 0, sizeof(new_ld->class_dev));
new_ld->class_dev.class = &lcd_class;
diff --git a/drivers/video/chipsfb.c b/drivers/video/chipsfb.c
index 73cb426..9a656bc 100644
--- a/drivers/video/chipsfb.c
+++ b/drivers/video/chipsfb.c
@@ -153,13 +153,11 @@
* useful at blank = 1 too (saves battery, extends backlight
* life)
*/
- down(&pmac_backlight->sem);
if (blank)
pmac_backlight->props->power = FB_BLANK_POWERDOWN;
else
pmac_backlight->props->power = FB_BLANK_UNBLANK;
- pmac_backlight->props->update_status(pmac_backlight);
- up(&pmac_backlight->sem);
+ backlight_update_status(pmac_backlight);
}
mutex_unlock(&pmac_backlight_mutex);
@@ -415,10 +413,8 @@
/* turn on the backlight */
mutex_lock(&pmac_backlight_mutex);
if (pmac_backlight) {
- down(&pmac_backlight->sem);
pmac_backlight->props->power = FB_BLANK_UNBLANK;
- pmac_backlight->props->update_status(pmac_backlight);
- up(&pmac_backlight->sem);
+ backlight_update_status(pmac_backlight);
}
mutex_unlock(&pmac_backlight_mutex);
#endif /* CONFIG_PMAC_BACKLIGHT */
diff --git a/drivers/video/nvidia/nv_backlight.c b/drivers/video/nvidia/nv_backlight.c
index 4254c09..f5e42d0 100644
--- a/drivers/video/nvidia/nv_backlight.c
+++ b/drivers/video/nvidia/nv_backlight.c
@@ -114,10 +114,8 @@
mutex_lock(&info->bl_mutex);
if (info->bl_dev) {
- down(&info->bl_dev->sem);
info->bl_dev->props->power = power;
__nvidia_bl_update_status(info->bl_dev);
- up(&info->bl_dev->sem);
}
mutex_unlock(&info->bl_mutex);
@@ -154,11 +152,9 @@
0x534 * FB_BACKLIGHT_MAX / MAX_LEVEL);
mutex_unlock(&info->bl_mutex);
- down(&bd->sem);
bd->props->brightness = nvidia_bl_data.max_brightness;
bd->props->power = FB_BLANK_UNBLANK;
- bd->props->update_status(bd);
- up(&bd->sem);
+ backlight_update_status(bd);
#ifdef CONFIG_PMAC_BACKLIGHT
mutex_lock(&pmac_backlight_mutex);
diff --git a/drivers/video/riva/fbdev.c b/drivers/video/riva/fbdev.c
index fd82571..b70d18f 100644
--- a/drivers/video/riva/fbdev.c
+++ b/drivers/video/riva/fbdev.c
@@ -357,10 +357,8 @@
mutex_lock(&info->bl_mutex);
if (info->bl_dev) {
- down(&info->bl_dev->sem);
info->bl_dev->props->power = power;
__riva_bl_update_status(info->bl_dev);
- up(&info->bl_dev->sem);
}
mutex_unlock(&info->bl_mutex);
@@ -397,11 +395,9 @@
FB_BACKLIGHT_MAX);
mutex_unlock(&info->bl_mutex);
- down(&bd->sem);
bd->props->brightness = riva_bl_data.max_brightness;
bd->props->power = FB_BLANK_UNBLANK;
- bd->props->update_status(bd);
- up(&bd->sem);
+ backlight_update_status(bd);
#ifdef CONFIG_PMAC_BACKLIGHT
mutex_lock(&pmac_backlight_mutex);
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 287c62d..d1426b8 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -9,8 +9,24 @@
#define _LINUX_BACKLIGHT_H
#include <linux/device.h>
+#include <linux/mutex.h>
#include <linux/notifier.h>
+/* Notes on locking:
+ *
+ * backlight_device->sem is an internal backlight lock protecting the props
+ * field and no code outside the core should need to touch it.
+ *
+ * Access to update_status() is serialised by the update_lock mutex since
+ * most drivers seem to need this and historically get it wrong.
+ *
+ * Most drivers don't need locking on their get_brightness() method.
+ * If yours does, you need to implement it in the driver. You can use the
+ * update_lock mutex if appropriate.
+ *
+ * Any other use of the locks below is probably wrong.
+ */
+
struct backlight_device;
struct fb_info;
@@ -44,12 +60,22 @@
struct semaphore sem;
/* If this is NULL, the backing module is unloaded */
struct backlight_properties *props;
+ /* Serialise access to update_status method */
+ struct mutex update_lock;
/* The framebuffer notifier block */
struct notifier_block fb_notif;
/* The class device structure */
struct class_device class_dev;
};
+static inline void backlight_update_status(struct backlight_device *bd)
+{
+ mutex_lock(&bd->update_lock);
+ if (bd->props && bd->props->update_status)
+ bd->props->update_status(bd);
+ mutex_unlock(&bd->update_lock);
+}
+
extern struct backlight_device *backlight_device_register(const char *name,
struct device *dev,void *devdata,struct backlight_properties *bp);
extern void backlight_device_unregister(struct backlight_device *bd);
diff --git a/include/linux/lcd.h b/include/linux/lcd.h
index 8a468f1..bfbf655 100644
--- a/include/linux/lcd.h
+++ b/include/linux/lcd.h
@@ -9,8 +9,24 @@
#define _LINUX_LCD_H
#include <linux/device.h>
+#include <linux/mutex.h>
#include <linux/notifier.h>
+/* Notes on locking:
+ *
+ * lcd_device->sem is an internal backlight lock protecting the props
+ * field and no code outside the core should need to touch it.
+ *
+ * Access to set_power() is serialised by the update_lock mutex since
+ * most drivers seem to need this and historically get it wrong.
+ *
+ * Most drivers don't need locking on their get_power() method.
+ * If yours does, you need to implement it in the driver. You can use the
+ * update_lock mutex if appropriate.
+ *
+ * Any other use of the locks below is probably wrong.
+ */
+
struct lcd_device;
struct fb_info;
@@ -39,12 +55,22 @@
struct semaphore sem;
/* If this is NULL, the backing module is unloaded */
struct lcd_properties *props;
+ /* Serialise access to set_power method */
+ struct mutex update_lock;
/* The framebuffer notifier block */
struct notifier_block fb_notif;
/* The class device structure */
struct class_device class_dev;
};
+static inline void lcd_set_power(struct lcd_device *ld, int power)
+{
+ mutex_lock(&ld->update_lock);
+ if (ld->props && ld->props->set_power)
+ ld->props->set_power(ld, power);
+ mutex_unlock(&ld->update_lock);
+}
+
extern struct lcd_device *lcd_device_register(const char *name,
void *devdata, struct lcd_properties *lp);
extern void lcd_device_unregister(struct lcd_device *ld);