+
+ /* Check the input/output of _BQC/_BCL/_BCM */
+ if ((max_level < 100) && (max_level <= (count - 2)))
+ br->flags._BCL_use_index = 1;
+
+ /*
+ * _BCM is always consistent with _BCL,
+ * at least for all the laptops we have ever seen.
+ */
+ br->flags._BCM_use_index = br->flags._BCL_use_index;
+
+ /* _BQC uses INDEX while _BCL uses VALUE in some laptops */
+ br->curr = max_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);
+ if (result)
+ goto out_free_levels;
+
+ result = acpi_video_device_lcd_get_level_current(device, &level);
+ 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;
+ }
+
+ ACPI_DEBUG_PRINT((ACPI_DB_INFO,
+ "found %d brightness levels\n", count - 2));