Message-ID: <20190424173146.b7vwdswl3btxyq7p@mail.google.com>
Date:   Thu, 25 Apr 2019 01:31:47 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Cc:     Changbin Du <changbin.du@...il.com>, mingo@...hat.com,
        Jonathan Corbet <corbet@....net>,
        Bjorn Helgaas <bhelgaas@...gle.com>, rjw@...ysocki.net,
        linux-pci@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, tglx@...utronix.de, x86@...nel.org,
        fenghua.yu@...el.com, linuxppc-dev@...ts.ozlabs.org,
        linux-acpi@...r.kernel.org, linux-gpio@...r.kernel.org
Subject: Re: [PATCH v4 24/63] Documentation: ACPI: move video_extension.txt
 to firmware-guide/acpi and convert to reST

On Wed, Apr 24, 2019 at 11:56:47AM -0300, Mauro Carvalho Chehab wrote:
> Em Wed, 24 Apr 2019 00:28:53 +0800
> Changbin Du <changbin.du@...il.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@...il.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
>
Thanks, done.

> > @@ -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.
> 	=====		===================
> 
> 
Done.

> > @@ -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

-- 
Cheers,
Changbin Du

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