ACPI / video: Fix applying indexed initial brightness value.

The value initially read via _BQC also needs to be offset by 2 to
compensate for the first 2 special items in _BCL. Introduce a helper
function that does the BQC-value-to-level conversion in order to not
needlessly duplicate code.

Signed-off-by: Danny Baumann <dannybaumann@web.de>
Reviewed-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 37 insertions, 23 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 8522d14972cf..3cdd0471bc63 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -458,6 +458,31 @@ static struct dmi_system_id video_dmi_table[] __initdata = {
         {}
 };
 
+static unsigned long long
+acpi_video_bqc_value_to_level(struct acpi_video_device *device,
+                              unsigned long long bqc_value)
+{
+        unsigned long long level;
+
+        if (device->brightness->flags._BQC_use_index) {
+                /*
+                 * _BQC returns an index that doesn't account for
+                 * the first 2 items with special meaning, so we need
+                 * to compensate for that by offsetting ourselves
+                 */
+                if (device->brightness->flags._BCL_reversed)
+                        bqc_value = device->brightness->count - 3 - bqc_value;
+
+                level = device->brightness->levels[bqc_value + 2];
+        } else {
+                level = bqc_value;
+        }
+
+        level += bqc_offset_aml_bug_workaround;
+
+        return level;
+}
+
 static int
 acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
                                         unsigned long long *level, bool raw)
@@ -480,14 +505,8 @@ acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
                                 return 0;
                         }
 
-                        if (device->brightness->flags._BQC_use_index) {
-                                if (device->brightness->flags._BCL_reversed)
-                                        *level = device->brightness->count
-                                                                 - 3 - (*level);
-                                *level = device->brightness->levels[*level + 2];
+                        *level = acpi_video_bqc_value_to_level(device, *level);
 
-                        }
-                        *level += bqc_offset_aml_bug_workaround;
                         for (i = 2; i < device->brightness->count; i++)
                                 if (device->brightness->levels[i] == *level) {
                                         device->brightness->curr = *level;
@@ -736,24 +755,19 @@ acpi_video_init_brightness(struct acpi_video_device *device)
 
         br->flags._BQC_use_index = (level == max_level ? 0 : 1);
 
-        if (!br->flags._BQC_use_index) {
+        if (use_bios_initial_backlight) {
+                level = acpi_video_bqc_value_to_level(device, level_old);
                 /*
-                 * Set the backlight to the initial state.
-                 * On some buggy laptops, _BQC returns an uninitialized value
-                 * when invoked for the first time, i.e. level_old is invalid.
-                 * set the backlight to max_level in this case
+                 * On some buggy laptops, _BQC returns an uninitialized
+                 * value when invoked for the first time, i.e.
+                 * level_old is invalid (no matter whether it's a level
+                 * or an index). Set the backlight to max_level in this case.
                  */
-                if (use_bios_initial_backlight) {
-                        for (i = 2; i < br->count; i++)
-                                if (level_old == br->levels[i]) {
-                                        level = level_old;
-                                        break;
-                                }
-                }
-        } else {
-                if (br->flags._BCL_reversed)
-                        level_old = (br->count - 1) - level_old;
-                level = br->levels[level_old];
+                for (i = 2; i < br->count; i++)
+                        if (level_old == br->levels[i])
+                                break;
+                if (i == br->count)
+                        level = max_level;
         }
 
 set_level: