1 files changed, 40 insertions, 1 deletions

diff --git a/drivers/acpi/video.c b/drivers/acpi/video.c
index 1705d947ea09..810cca90ca7f 100644
--- a/drivers/acpi/video.c
+++ b/drivers/acpi/video.c
@@ -538,6 +538,41 @@ acpi_video_device_lcd_set_level(struct acpi_video_device *device, int level)
         return -EINVAL;
 }
 
+/*
+ * For some buggy _BQC methods, we need to add a constant value to
+ * the _BQC return value to get the actual current brightness level
+ */
+
+static int bqc_offset_aml_bug_workaround;
+static int __init video_set_bqc_offset(const struct dmi_system_id *d)
+{
+        bqc_offset_aml_bug_workaround = 9;
+        return 0;
+}
+
+static struct dmi_system_id video_dmi_table[] __initdata = {
+        /*
+         * Broken _BQC workaround http://bugzilla.kernel.org/show_bug.cgi?id=13121
+         */
+        {
+         .callback = video_set_bqc_offset,
+         .ident = "Acer Aspire 5720",
+         .matches = {
+                DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+                DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5720"),
+                },
+        },
+        {
+         .callback = video_set_bqc_offset,
+         .ident = "Acer Aspire 5710Z",
+         .matches = {
+                DMI_MATCH(DMI_BOARD_VENDOR, "Acer"),
+                DMI_MATCH(DMI_PRODUCT_NAME, "Aspire 5710Z"),
+                },
+        },
+        {}
+};
+
 static int
 acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
                                         unsigned long long *level)
@@ -557,6 +592,7 @@ acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
                                 *level = device->brightness->levels[*level + 2];
 
                         }
+                        *level += bqc_offset_aml_bug_workaround;
                         device->brightness->curr = *level;
                         return 0;
                 } else {
@@ -2290,13 +2326,15 @@ EXPORT_SYMBOL(acpi_video_register);
 
 static int __init acpi_video_init(void)
 {
+        dmi_check_system(video_dmi_table);
+
         if (intel_opregion_present())
                 return 0;
 
         return acpi_video_register();
 }
 
-static void __exit acpi_video_exit(void)
+void __exit acpi_video_exit(void)
 {
 
         acpi_bus_unregister_driver(&acpi_video_bus);
@@ -2305,6 +2343,7 @@ static void __exit acpi_video_exit(void)
 
         return;
 }
+EXPORT_SYMBOL(acpi_video_exit);
 
 module_init(acpi_video_init);
 module_exit(acpi_video_exit);