* [PATCH 1/3] ACPI / video: add description for brightness_switch_enabled
2013-06-20 7:08 [PATCH 0/3] ACPI video driver document update Aaron Lu
@ 2013-06-20 7:08 ` Aaron Lu
2013-06-20 7:08 ` [PATCH 2/3] ACPI / video: move video_extension.txt to Documentation/acpi Aaron Lu
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: Aaron Lu @ 2013-06-20 7:08 UTC (permalink / raw)
To: Rafael J. Wysocki; +Cc: Micael Dias, Zhang Rui, linux-acpi, Len Brown
Add description for video module's parameter brightness_switch_enabled
into kernel-parameters.txt.
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
---
Documentation/kernel-parameters.txt | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 2fe6e76..7f64e0f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -3229,6 +3229,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
video= [FB] Frame buffer configuration
See Documentation/fb/modedb.txt.
+ video.brightness_switch_enabled= [0,1]
+ If set to 1, on receiving an ACPI notify event
+ generated by hotkey, video driver will adjust brightness
+ level and then send out the event to user space through
+ the allocated input device; If set to 0, video driver
+ will only send out the event without touching backlight
+ brightness level.
+ default: 1
+
virtio_mmio.device=
[VMMIO] Memory mapped virtio (platform) device.
--
1.8.3.3.gfada522
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH 3/3] ACPI / video: update video_extension.txt for backlight control
2013-06-20 7:08 [PATCH 0/3] ACPI video driver document update Aaron Lu
2013-06-20 7:08 ` [PATCH 1/3] ACPI / video: add description for brightness_switch_enabled Aaron Lu
2013-06-20 7:08 ` [PATCH 2/3] ACPI / video: move video_extension.txt to Documentation/acpi Aaron Lu
@ 2013-06-20 7:08 ` Aaron Lu
2013-06-24 12:01 ` [PATCH 0/3] ACPI video driver document update Rafael J. Wysocki
3 siblings, 0 replies; 5+ messages in thread
From: Aaron Lu @ 2013-06-20 7:08 UTC (permalink / raw)
To: Rafael J. Wysocki; +Cc: Micael Dias, Zhang Rui, linux-acpi, Len Brown
The ACPI video driver has changed a lot, and it doesn't export
interfaces in /proc any more, so the documentation for it should
be updated.
This update focuses on ACPI video driver's backlight control.
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
---
Documentation/acpi/video_extension.txt | 121 ++++++++++++++++++++++++++-------
1 file changed, 95 insertions(+), 26 deletions(-)
diff --git a/Documentation/acpi/video_extension.txt b/Documentation/acpi/video_extension.txt
index b2f9b15..78b32ac 100644
--- a/Documentation/acpi/video_extension.txt
+++ b/Documentation/acpi/video_extension.txt
@@ -8,30 +8,99 @@ defining the video POST device, retrieving EDID information or to
setup a video output, etc. Note that this is an ref. implementation
only. It may or may not work for your integrated video device.
-Interfaces exposed to userland through /proc/acpi/video:
-
-VGA/info : display the supported video bus device capability like Video ROM, CRT/LCD/TV.
-VGA/ROM : Used to get a copy of the display devices' ROM data (up to 4k).
-VGA/POST_info : Used to determine what options are implemented.
-VGA/POST : Used to get/set POST device.
-VGA/DOS : Used to get/set ownership of output switching:
- Please refer ACPI spec B.4.1 _DOS
-VGA/CRT : CRT output
-VGA/LCD : LCD output
-VGA/TVO : TV output
-VGA/*/brightness : Used to get/set brightness of output device
-
-Notify event through /proc/acpi/event:
-
-#define ACPI_VIDEO_NOTIFY_SWITCH 0x80
-#define ACPI_VIDEO_NOTIFY_PROBE 0x81
-#define ACPI_VIDEO_NOTIFY_CYCLE 0x82
-#define ACPI_VIDEO_NOTIFY_NEXT_OUTPUT 0x83
-#define ACPI_VIDEO_NOTIFY_PREV_OUTPUT 0x84
-
-#define ACPI_VIDEO_NOTIFY_CYCLE_BRIGHTNESS 0x82
-#define ACPI_VIDEO_NOTIFY_INC_BRIGHTNESS 0x83
-#define ACPI_VIDEO_NOTIFY_DEC_BRIGHTNESS 0x84
-#define ACPI_VIDEO_NOTIFY_ZERO_BRIGHTNESS 0x85
-#define ACPI_VIDEO_NOTIFY_DISPLAY_OFF 0x86
+The ACPI video driver does 3 things regarding backlight control:
+1 Export a sysfs interface for user space to control backlight level
+
+If the ACPI table has a video device, and acpi_backlight=vendor kernel
+command line is not present, the driver will register a backlight device
+and set the required backlight operation structure for it for the sysfs
+interface control. For every registered class device, there will be a
+directory named acpi_videoX under /sys/class/backlight.
+
+The backlight sysfs interface has a standard definition here:
+Documentation/ABI/stable/sysfs-class-backlight.
+
+And what ACPI video driver does is:
+actual_brightness: on read, control method _BQC will be evaluated to
+get the brightness level the firmware thinks it is at;
+bl_power: not implemented, will set the current brightness instead;
+brightness: on write, control method _BCM will run to set the requested
+brightness level;
+max_brightness: Derived from the _BCL package(see below);
+type: firmware
+
+Note that ACPI video backlight driver will always use index for
+brightness, actual_brightness and max_brightness. So if we have
+the following _BCL package:
+
+Method (_BCL, 0, NotSerialized)
+{
+ Return (Package (0x0C)
+ {
+ 0x64,
+ 0x32,
+ 0x0A,
+ 0x14,
+ 0x1E,
+ 0x28,
+ 0x32,
+ 0x3C,
+ 0x46,
+ 0x50,
+ 0x5A,
+ 0x64
+ })
+}
+
+The first two levels are for when laptop are on AC or on battery and are
+not used by Linux currently. The remaining 10 levels are supported levels
+that we can choose from. The applicable index values are from 0 (that
+corresponds to the 0x0A brightness value) to 9 (that corresponds to the
+0x64 brightness value) inclusive. Each of those index values is regarded
+as a "brightness level" indicator. Thus from the user space perspective
+the range of available brightness levels is from 0 to 9 (max_brightness)
+inclusive.
+
+2 Notify user space about hotkey event
+
+There are generally two cases for hotkey event reporting:
+i) For some laptops, when user presses the hotkey, a scancode will be
+ generated and sent to user space through the input device created by
+ the keyboard driver as a key type input event, with proper remap, the
+ following key code will appear to user space:
+
+ EV_KEY, KEY_BRIGHTNESSUP
+ EV_KEY, KEY_BRIGHTNESSDOWN
+ etc.
+
+For this case, ACPI video driver does not need to do anything(actually,
+it doesn't even know this happened).
+
+ii) For some laptops, the press of the hotkey will not generate the
+ scancode, instead, firmware will notify the video device ACPI node
+ about the event. The event value is defined in the ACPI spec. ACPI
+ video driver will generate an key type input event according to the
+ notify value it received and send the event to user space through the
+ input device it created:
+
+ event keycode
+ 0x86 KEY_BRIGHTNESSUP
+ 0x87 KEY_BRIGHTNESSDOWN
+ etc.
+
+so this would lead to the same effect as case i) now.
+
+Once user space tool receives this event, it can modify the backlight
+level through the sysfs interface.
+
+3 Change backlight level in the kernel
+
+This works for machines covered by case ii) in Section 2. Once the driver
+received a notification, it will set the backlight level accordingly. This does
+not affect the sending of event to user space, they are always sent to user
+space regardless of whether or not the video module controls the backlight level
+directly. This behaviour can be controlled through the brightness_switch_enabled
+module parameter as documented in kernel-parameters.txt. It is recommended to
+disable this behaviour once a GUI environment starts up and wants to have full
+control of the backlight level.
--
1.8.3.3.gfada522
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH 0/3] ACPI video driver document update
2013-06-20 7:08 [PATCH 0/3] ACPI video driver document update Aaron Lu
` (2 preceding siblings ...)
2013-06-20 7:08 ` [PATCH 3/3] ACPI / video: update video_extension.txt for backlight control Aaron Lu
@ 2013-06-24 12:01 ` Rafael J. Wysocki
3 siblings, 0 replies; 5+ messages in thread
From: Rafael J. Wysocki @ 2013-06-24 12:01 UTC (permalink / raw)
To: Aaron Lu; +Cc: Micael Dias, Zhang Rui, linux-acpi, Len Brown
On Thursday, June 20, 2013 03:08:54 PM Aaron Lu wrote:
> ACPI video driver's document is pretty outdated and needs updating.
> Patch 1 adds description for brightness_switch_enabled kernel command
> line option;
> Patch 2 moves the document for ACPI video driver from Documentation/power
> to Documentation/ACPI, since it is a document for the ACPI video driver;
> Patch 3 updates the video driver's document by focusing on how backlight
> is controlled by it.
>
> Aaron Lu (3):
> ACPI / video: add description for brightness_switch_enabled
> ACPI / video: move video_extension.txt to Documentation/acpi
> ACPI / video: update video_extension.txt for backlight control
>
> Documentation/acpi/video_extension.txt | 106 ++++++++++++++++++++++++++++++++
> Documentation/kernel-parameters.txt | 9 +++
> Documentation/power/video_extension.txt | 37 -----------
> 3 files changed, 115 insertions(+), 37 deletions(-)
> create mode 100644 Documentation/acpi/video_extension.txt
> delete mode 100644 Documentation/power/video_extension.txt
All queued up for 3.11.
Thanks,
Rafael
^ permalink raw reply [flat|nested] 5+ messages in thread