[PATCH] backlight: Backlight Class Improvements

Backlight class attributes are currently easy to implement incorrectly.
Moving certain handling into the backlight core prevents this whilst at the
same time makes the drivers simpler and consistent.  The following changes are
included:

The brightness attribute only sets and reads the brightness variable in the
backlight_properties structure.

The power attribute only sets and reads the power variable in the
backlight_properties structure.

Any framebuffer blanking events change a variable fb_blank in the
backlight_properties structure.

The backlight driver has only two functions to implement.  One function is
called when any of the above properties change (to update the backlight
brightness), the second is called to return the current backlight brightness
value.  A new attribute "actual_brightness" is added to return this brightness
as determined by the driver having combined all the above factors (and any
driver/device specific factors).

Additionally, the backlight core takes care of checking the maximum brightness
is not exceeded and of turning off the backlight before device removal.

The corgi backlight driver is updated to reflect these changes.

Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 56 insertions, 28 deletions

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 151fda8dded0..334b1db1bd7c 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -16,14 +16,12 @@
 
 static ssize_t backlight_show_power(struct class_device *cdev, char *buf)
 {
-        int rc;
+        int rc = -ENXIO;
         struct backlight_device *bd = to_backlight_device(cdev);
 
         down(&bd->sem);
-        if (likely(bd->props && bd->props->get_power))
-                rc = sprintf(buf, "%d\n", bd->props->get_power(bd));
-        else
-                rc = -ENXIO;
+        if (likely(bd->props))
+                rc = sprintf(buf, "%d\n", bd->props->power);
         up(&bd->sem);
 
         return rc;
@@ -31,7 +29,7 @@ static ssize_t backlight_show_power(struct class_device *cdev, char *buf)
 
 static ssize_t backlight_store_power(struct class_device *cdev, const char *buf, size_t count)
 {
-        int rc, power;
+        int rc = -ENXIO, power;
         char *endp;
         struct backlight_device *bd = to_backlight_device(cdev);
 
@@ -40,12 +38,13 @@ static ssize_t backlight_store_power(struct class_device *cdev, const char *buf,
                 return -EINVAL;
 
         down(&bd->sem);
-        if (likely(bd->props && bd->props->set_power)) {
+        if (likely(bd->props)) {
                 pr_debug("backlight: set power to %d\n", power);
-                bd->props->set_power(bd, power);
+                bd->props->power = power;
+                if (likely(bd->props->update_status))
+                        bd->props->update_status(bd);
                 rc = count;
-        } else
-                rc = -ENXIO;
+        }
         up(&bd->sem);
 
         return rc;
@@ -53,14 +52,12 @@ static ssize_t backlight_store_power(struct class_device *cdev, const char *buf,
 
 static ssize_t backlight_show_brightness(struct class_device *cdev, char *buf)
 {
-        int rc;
+        int rc = -ENXIO;
         struct backlight_device *bd = to_backlight_device(cdev);
 
         down(&bd->sem);
-        if (likely(bd->props && bd->props->get_brightness))
-                rc = sprintf(buf, "%d\n", bd->props->get_brightness(bd));
-        else
-                rc = -ENXIO;
+        if (likely(bd->props))
+                rc = sprintf(buf, "%d\n", bd->props->brightness);
         up(&bd->sem);
 
         return rc;
@@ -68,7 +65,7 @@ static ssize_t backlight_show_brightness(struct class_device *cdev, char *buf)
 
 static ssize_t backlight_store_brightness(struct class_device *cdev, const char *buf, size_t count)
 {
-        int rc, brightness;
+        int rc = -ENXIO, brightness;
         char *endp;
         struct backlight_device *bd = to_backlight_device(cdev);
 
@@ -77,12 +74,18 @@ static ssize_t backlight_store_brightness(struct class_device *cdev, const char
                 return -EINVAL;
 
         down(&bd->sem);
-        if (likely(bd->props && bd->props->set_brightness)) {
-                pr_debug("backlight: set brightness to %d\n", brightness);
-                bd->props->set_brightness(bd, brightness);
-                rc = count;
-        } else
-                rc = -ENXIO;
+        if (likely(bd->props)) {
+                if (brightness > bd->props->max_brightness)
+                        rc = -EINVAL;
+                else {
+                        pr_debug("backlight: set brightness to %d\n",
+                                 brightness);
+                        bd->props->brightness = brightness;
+                        if (likely(bd->props->update_status))
+                                bd->props->update_status(bd);
+                        rc = count;
+                }
+        }
         up(&bd->sem);
 
         return rc;
@@ -90,14 +93,26 @@ static ssize_t backlight_store_brightness(struct class_device *cdev, const char
 
 static ssize_t backlight_show_max_brightness(struct class_device *cdev, char *buf)
 {
-        int rc;
+        int rc = -ENXIO;
         struct backlight_device *bd = to_backlight_device(cdev);
 
         down(&bd->sem);
         if (likely(bd->props))
                 rc = sprintf(buf, "%d\n", bd->props->max_brightness);
-        else
-                rc = -ENXIO;
+        up(&bd->sem);
+
+        return rc;
+}
+
+static ssize_t backlight_show_actual_brightness(struct class_device *cdev,
+                                                char *buf)
+{
+        int rc = -ENXIO;
+        struct backlight_device *bd = to_backlight_device(cdev);
+
+        down(&bd->sem);
+        if (likely(bd->props && bd->props->get_brightness))
+                rc = sprintf(buf, "%d\n", bd->props->get_brightness(bd));
         up(&bd->sem);
 
         return rc;
@@ -123,7 +138,10 @@ static struct class backlight_class = {
 
 static struct class_device_attribute bl_class_device_attributes[] = {
         DECLARE_ATTR(power, 0644, backlight_show_power, backlight_store_power),
-        DECLARE_ATTR(brightness, 0644, backlight_show_brightness, backlight_store_brightness),
+        DECLARE_ATTR(brightness, 0644, backlight_show_brightness,
+                     backlight_store_brightness),
+        DECLARE_ATTR(actual_brightness, 0444, backlight_show_actual_brightness,
+                     NULL),
         DECLARE_ATTR(max_brightness, 0444, backlight_show_max_brightness, NULL),
 };
 
@@ -144,8 +162,12 @@ static int fb_notifier_callback(struct notifier_block *self,
         bd = container_of(self, struct backlight_device, fb_notif);
         down(&bd->sem);
         if (bd->props)
-                if (!bd->props->check_fb || bd->props->check_fb(evdata->info))
-                        bd->props->set_power(bd, *(int *)evdata->data);
+                if (!bd->props->check_fb ||
+                    bd->props->check_fb(evdata->info)) {
+                        bd->props->fb_blank = *(int *)evdata->data;
+                        if (likely(bd->props && bd->props->update_status))
+                                bd->props->update_status(bd);
+                }
         up(&bd->sem);
         return 0;
 }
@@ -231,6 +253,12 @@ void backlight_device_unregister(struct backlight_device *bd)
                                          &bl_class_device_attributes[i]);
 
         down(&bd->sem);
+        if (likely(bd->props && bd->props->update_status)) {
+                bd->props->brightness = 0;
+                bd->props->power = 0;
+                bd->props->update_status(bd);
+        }
+
         bd->props = NULL;
         up(&bd->sem);