thinkpad-acpi: issue backlight class events

Take advantage of the new events capabilities of the backlight class to
notify userspace of backlight changes.

This depends on "backlight: Allow drivers to update the core, and
generate events on changes", by Matthew Garrett.
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

Documentation/laptops/thinkpad-acpi.txt

@@ -460,6 +460,8 @@ event	code	Key		Notes
 				For Lenovo ThinkPads with a new
 				BIOS, it has to be handled either
 				by the ACPI OSI, or by userspace.
+				The driver does the right thing,
+				never mess with this.
 0x1011	0x10	FN+END		Brightness down.  See brightness
 				up for details.
 
@@ -582,46 +584,15 @@ with hotkey_report_mode.
 
 Brightness hotkey notes:
 
-These are the current sane choices for brightness key mapping in
-thinkpad-acpi:
+Don't mess with the brightness hotkeys in a Thinkpad.  If you want
+notifications for OSD, use the sysfs backlight class event support.
 
-For IBM and Lenovo models *without* ACPI backlight control (the ones on
-which thinkpad-acpi will autoload its backlight interface by default,
-and on which ACPI video does not export a backlight interface):
-
-1. Don't enable or map the brightness hotkeys in thinkpad-acpi, as
-   these older firmware versions unfortunately won't respect the hotkey
-   mask for brightness keys anyway, and always reacts to them.  This
-   usually work fine, unless X.org drivers are doing something to block
-   the BIOS.  In that case, use (3) below.  This is the default mode of
-   operation.
-
-2. Enable the hotkeys, but map them to something else that is NOT
-   KEY_BRIGHTNESS_UP/DOWN or any other keycode that would cause
-   userspace to try to change the backlight level, and use that as an
-   on-screen-display hint.
-
-3. IF AND ONLY IF X.org drivers find a way to block the firmware from
-   automatically changing the brightness, enable the hotkeys and map
-   them to KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN, and feed that to
-   something that calls xbacklight.  thinkpad-acpi will not be able to
-   change brightness in that case either, so you should disable its
-   backlight interface.
-
-For Lenovo models *with* ACPI backlight control:
-
-1. Load up ACPI video and use that.  ACPI video will report ACPI
-   events for brightness change keys.  Do not mess with thinkpad-acpi
-   defaults in this case.  thinkpad-acpi should not have anything to do
-   with backlight events in a scenario where ACPI video is loaded:
-   brightness hotkeys must be disabled, and the backlight interface is
-   to be kept disabled as well.  This is the default mode of operation.
-
-2. Do *NOT* load up ACPI video, enable the hotkeys in thinkpad-acpi,
-   and map them to KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN.  Process
-   these keys on userspace somehow (e.g. by calling xbacklight).
-   The driver will do this automatically if it detects that ACPI video
-   has been disabled.
+The driver will issue KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN events
+automatically for the cases were userspace has to do something to
+implement brightness changes.  When you override these events, you will
+either fail to handle properly the ThinkPads that require explicit
+action to change backlight brightness, or the ThinkPads that require
+that no action be taken to work properly.
 
 
 Bluetooth
@@ -1465,3 +1436,5 @@ Sysfs interface changelog:
 		and it is always able to disable hot keys.  Very old
 		thinkpads are properly supported.  hotkey_bios_mask
 		is deprecated and marked for removal.
+
+0x020600:	Marker for backlight change event support.

drivers/platform/x86/thinkpad_acpi.c

@@ -22,7 +22,7 @@
  */
 
 #define TPACPI_VERSION "0.23"
-#define TPACPI_SYSFS_VERSION 0x020500
+#define TPACPI_SYSFS_VERSION 0x020600
 
 /*
  *  Changelog:
@@ -6073,6 +6073,12 @@ static int brightness_get(struct backlight_device *bd)
 	return status & TP_EC_BACKLIGHT_LVLMSK;
 }
 
+static void tpacpi_brightness_notify_change(void)
+{
+	backlight_force_update(ibm_backlight_device,
+			       BACKLIGHT_UPDATE_HOTKEY);
+}
+
 static struct backlight_ops ibm_backlight_data = {
 	.get_brightness = brightness_get,
 	.update_status  = brightness_update_status,
@@ -6227,6 +6233,12 @@ static int __init brightness_init(struct ibm_init_struct *iibm)
 	ibm_backlight_device->props.brightness = b & TP_EC_BACKLIGHT_LVLMSK;
 	backlight_update_status(ibm_backlight_device);
 
+	vdbg_printk(TPACPI_DBG_INIT | TPACPI_DBG_BRGHT,
+			"brightness: registering brightness hotkeys "
+			"as change notification\n");
+	tpacpi_hotkey_driver_mask_set(hotkey_driver_mask
+				| TP_ACPI_HKEY_BRGHTUP_MASK
+				| TP_ACPI_HKEY_BRGHTDWN_MASK);;
 	return 0;
 }
 
@@ -6303,6 +6315,9 @@ static int brightness_write(char *buf)
 	 * Doing it this way makes the syscall restartable in case of EINTR
 	 */
 	rc = brightness_set(level);
+	if (!rc && ibm_backlight_device)
+		backlight_force_update(ibm_backlight_device,
+					BACKLIGHT_UPDATE_SYSFS);
 	return (rc == -EINTR)? -ERESTARTSYS : rc;
 }
 
@@ -7702,6 +7717,13 @@ static struct ibm_struct fan_driver_data = {
  */
 static void tpacpi_driver_event(const unsigned int hkey_event)
 {
+	if (ibm_backlight_device) {
+		switch (hkey_event) {
+		case TP_HKEY_EV_BRGHT_UP:
+		case TP_HKEY_EV_BRGHT_DOWN:
+			tpacpi_brightness_notify_change();
+		}
+	}
 }