ACPI: video: Add new hw_changes_brightness quirk, set it on PB Easynote MZ35

Some machines change the brightness themselves when a brightness hotkey
gets pressed, despite us telling them not to. This causes the brightness to
go two steps up / down when the hotkey is pressed. This is esp. a problem
on older machines with only a few brightness levels.

This commit adds a new hw_changes_brightness quirk which makes
acpi_video_device_notify() only call backlight_force_update(...,
BACKLIGHT_UPDATE_HOTKEY) and not do anything else, notifying userspace
that the brightness was changed and leaving it at that fixing the dual
step problem.

BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=204077
Reported-by: Kacper Piwiński <cosiekvfj@o2.pl>
Tested-by: Kacper Piwiński <cosiekvfj@o2.pl>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 9489ffc0641179a17acea826cc2ff5e2fe63866b..4f325e47519f586b07708fbe4486b79a221ca8a9 100644 (file)
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -60,6 +60,12 @@ module_param(report_key_events, int, 0644);
 MODULE_PARM_DESC(report_key_events,
        "0: none, 1: output changes, 2: brightness changes, 3: all");
 
+static int hw_changes_brightness = -1;
+module_param(hw_changes_brightness, int, 0644);
+MODULE_PARM_DESC(hw_changes_brightness,
+       "Set this to 1 on buggy hw which changes the brightness itself when "
+       "a hotkey is pressed: -1: auto, 0: normal 1: hw-changes-brightness");
+
 /*
  * Whether the struct acpi_video_device_attrib::device_id_scheme bit should be
  * assumed even if not actually set.
@@ -405,6 +411,14 @@ static int video_set_report_key_events(const struct dmi_system_id *id)
        return 0;
 }
 
+static int video_hw_changes_brightness(
+       const struct dmi_system_id *d)
+{
+       if (hw_changes_brightness == -1)
+               hw_changes_brightness = 1;
+       return 0;
+}
+
 static const struct dmi_system_id video_dmi_table[] = {
        /*
         * Broken _BQC workaround http://bugzilla.kernel.org/show_bug.cgi?id=13121
@@ -529,6 +543,21 @@ static const struct dmi_system_id video_dmi_table[] = {
                DMI_MATCH(DMI_PRODUCT_NAME, "Vostro V131"),
                },
        },
+       /*
+        * Some machines change the brightness themselves when a brightness
+        * hotkey gets pressed, despite us telling them not to. In this case
+        * acpi_video_device_notify() should only call backlight_force_update(
+        * BACKLIGHT_UPDATE_HOTKEY) and not do anything else.
+        */
+       {
+        /* https://bugzilla.kernel.org/show_bug.cgi?id=204077 */
+        .callback = video_hw_changes_brightness,
+        .ident = "Packard Bell EasyNote MZ35",
+        .matches = {
+               DMI_MATCH(DMI_SYS_VENDOR, "Packard Bell"),
+               DMI_MATCH(DMI_PRODUCT_NAME, "EasyNote MZ35"),
+               },
+       },
        {}
 };
 
@@ -1612,6 +1641,14 @@ static void acpi_video_device_notify(acpi_handle handle, u32 event, void *data)
        bus = video_device->video;
        input = bus->input;
 
+       if (hw_changes_brightness > 0) {
+               if (video_device->backlight)
+                       backlight_force_update(video_device->backlight,
+                                              BACKLIGHT_UPDATE_HOTKEY);
+               acpi_notifier_call_chain(device, event, 0);
+               return;
+       }
+
        switch (event) {
        case ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS:        /* Cycle brightness */
                brightness_switch_event(video_device, event);