ACPI video: handle indexed _BQC correctly

In the current code, for a box with an indexed _BQC method, we
1. get the current brightness level by evaluating _BQC
2. set the value gotten in step 1 to _BCM
3. get the current brightness level again
4. set the _BQC_use_index flag if the results gotten
   in step 1 and in step 3 don't equal.

But this logic doesn't work actually, because the _BQC_use_index
is not set when acpi_video_device_lcd_set_level is invoked.
This results in a failure in step 2.
http://bugzilla.kernel.org/show_bug.cgi?id=12249#c83

Now, we set the _BQC_use_index flag after invoking _BQC for the first
time. And reevaluate the _BQC to get the correct brightness level.

Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 22 insertions, 21 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index cd4fb7543a90..346277f93cda 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -807,12 +807,19 @@ acpi_video_init_brightness(struct acpi_video_device *device)
         br->flags._BCM_use_index = br->flags._BCL_use_index;
 
         /* _BQC uses INDEX while _BCL uses VALUE in some laptops */
-        br->curr = max_level;
+        br->curr = level_old = max_level;
+
+        if (!device->cap._BQC)
+                goto set_level;
+
         result = acpi_video_device_lcd_get_level_current(device, &level_old);
         if (result)
                 goto out_free_levels;
 
-        result = acpi_video_device_lcd_set_level(device, br->curr);
+        /*
+         * Set the level to maximum and check if _BQC uses indexed value
+         */
+        result = acpi_video_device_lcd_set_level(device, max_level);
         if (result)
                 goto out_free_levels;
 
@@ -820,25 +827,19 @@ acpi_video_init_brightness(struct acpi_video_device *device)
         if (result)
                 goto out_free_levels;
 
-        if ((level != level_old) && !br->flags._BCM_use_index) {
-                /* Note:
-                 * This piece of code does not work correctly if the current
-                 * brightness levels is 0.
-                 * But I guess boxes that boot with such a dark screen are rare
-                 * and no more code is needed to cover this specifial case.
-                 */
-
-                if (level_ac_battery != 2) {
-                        /*
-                         * For now, we don't support the _BCL like this:
-                         * 16, 15, 0, 1, 2, 3, ..., 14, 15, 16
-                         * because we may mess up the index returned by _BQC.
-                         * Plus: we have not got a box like this.
-                         */
-                        ACPI_ERROR((AE_INFO, "_BCL not supported\n"));
-                }
-                br->flags._BQC_use_index = 1;
-        }
+        br->flags._BQC_use_index = (level == max_level ? 0 : 1);
+
+        if (!br->flags._BQC_use_index)
+                goto set_level;
+
+        if (br->flags._BCL_reversed)
+                level_old = (br->count - 1) - level_old;
+        level_old = br->levels[level_old];
+
+set_level:
+        result = acpi_video_device_lcd_set_level(device, level_old);
+        if (result)
+                goto out_free_levels;
 
         ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                           "found %d brightness levels\n", count - 2));