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 \feffacpi_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>

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index cd4fb75..346277f 100644 (file)
--- 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));