Re: [PATCH v4 24/63] Documentation: ACPI: move video_extension.txt to firmware-guide/acpi and convert to reST

Mauro Carvalho Chehab
2019-04-24T14:57:05Z

Em Wed, 24 Apr 2019 00:28:53 +0800
Changbin Du <changbin.du@gmail.com> escreveu:

> This converts the plain text documentation to reStructuredText format and
> add it to Sphinx TOC tree. No essential content change.
>
> Signed-off-by: Changbin Du <changbin.du@gmail.com>
> ---
> Documentation/firmware-guide/acpi/index.rst | 1 +
> .../acpi/video_extension.rst} | 63 ++++++++++---------
> 2 files changed, 36 insertions(+), 28 deletions(-)
> rename Documentation/{acpi/video_extension.txt => firmware-guide/acpi/video_extension.rst} (79%)
>
> diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst
> index 0e60f4b7129a..ae609eec4679 100644
> --- a/Documentation/firmware-guide/acpi/index.rst
> +++ b/Documentation/firmware-guide/acpi/index.rst
> @@ -23,3 +23,4 @@ ACPI Support
> i2c-muxes
> acpi-lid
> lpit
> + video_extension
> diff --git a/Documentation/acpi/video_extension.txt b/Documentation/firmware-guide/acpi/video_extension.rst
> similarity index 79%
> rename from Documentation/acpi/video_extension.txt
> rename to Documentation/firmware-guide/acpi/video_extension.rst
> index 79bf6a4921be..06f7e3230b6e 100644
> --- a/Documentation/acpi/video_extension.txt
> +++ b/Documentation/firmware-guide/acpi/video_extension.rst
> @@ -1,5 +1,8 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +=====================
> ACPI video extensions
> -~~~~~~~~~~~~~~~~~~~~~
> +=====================
>
> This driver implement the ACPI Extensions For Display Adapters for
> integrated graphics devices on motherboard, as specified in ACPI 2.0
> @@ -8,9 +11,10 @@ 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.
>
> -The ACPI video driver does 3 things regarding backlight control:
> +The ACPI video driver does 3 things regarding backlight control.
>
> -1 Export a sysfs interface for user space to control backlight level
> +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

Hmm... you didn't touch on this part of the document:

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

You should touch it. My suggestion here is:

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

> @@ -32,26 +36,26 @@ 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:
> +the following _BCL package::
>
> -Method (_BCL, 0, NotSerialized)
> -{
> - Return (Package (0x0C)
> + Method (_BCL, 0, NotSerialized)
> {
> - 0x64,
> - 0x32,
> - 0x0A,
> - 0x14,
> - 0x1E,
> - 0x28,
> - 0x32,
> - 0x3C,
> - 0x46,
> - 0x50,
> - 0x5A,
> - 0x64
> - })
> -}
> + 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
> @@ -62,13 +66,15 @@ 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
> +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:
> + following key code will appear to user space::
>
> EV_KEY, KEY_BRIGHTNESSUP
> EV_KEY, KEY_BRIGHTNESSDOWN
> @@ -82,7 +88,7 @@ ii) For some laptops, the press of the hotkey will not generate the
> 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:
> + input device it created::
>
> event keycode
> 0x86 KEY_BRIGHTNESSUP

Perhaps making this as a table would work better:

input device it created:

===== ===================
event keycode
===== ===================
0x86 KEY_BRIGHTNESSUP
0x87 KEY_BRIGHTNESSDOWN
etc.
===== ===================

> @@ -94,13 +100,14 @@ 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
> +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 admin-guide/kernel-parameters.rst. It is recommended to
> -disable this behaviour once a GUI environment starts up and wants to have full
> -control of the backlight level.
> +module parameter as documented in admin-guide/kernel-parameters.rst. It is
> +recommended to disable this behaviour once a GUI environment starts up and
> +wants to have full control of the backlight level.

Thanks,
Mauro