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Date:   Tue, 23 Apr 2019 18:12:36 -0300
From:   Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
To:     Changbin Du <changbin.du@gmail.com>
Cc:     Jonathan Corbet <corbet@lwn.net>,
        Bjorn Helgaas <bhelgaas@google.com>, rjw@rjwysocki.net,
        linux-pci@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, tglx@linutronix.de, mingo@redhat.com,
        x86@kernel.org, fenghua.yu@intel.com,
        linuxppc-dev@lists.ozlabs.org, linux-acpi@vger.kernel.org,
        linux-gpio@vger.kernel.org
Subject: Re: [PATCH v4 13/63] Documentation: ACPI: move acpi-lid.txt to
 firmware-guide/acpi and convert to reST
Message-ID: <20190423181236.18e4b6a0@coco.lan>
In-Reply-To: <20190423162932.21428-14-changbin.du@gmail.com>
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        <20190423162932.21428-14-changbin.du@gmail.com>
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Em Wed, 24 Apr 2019 00:28:42 +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>
> ---
>  .../acpi/acpi-lid.rst}                        | 48 ++++++++++++-------
>  Documentation/firmware-guide/acpi/index.rst   |  1 +
>  2 files changed, 33 insertions(+), 16 deletions(-)
>  rename Documentation/{acpi/acpi-lid.txt => firmware-guide/acpi/acpi-lid.rst} (77%)
> 
> diff --git a/Documentation/acpi/acpi-lid.txt b/Documentation/firmware-guide/acpi/acpi-lid.rst
> similarity index 77%
> rename from Documentation/acpi/acpi-lid.txt
> rename to Documentation/firmware-guide/acpi/acpi-lid.rst
> index effe7af3a5af..1d19e15a6945 100644
> --- a/Documentation/acpi/acpi-lid.txt
> +++ b/Documentation/firmware-guide/acpi/acpi-lid.rst
> @@ -1,25 +1,29 @@
> -Special Usage Model of the ACPI Control Method Lid Device
> +.. SPDX-License-Identifier: GPL-2.0
> +.. include:: <isonum.txt>
>  
> -Copyright (C) 2016, Intel Corporation
> -Author: Lv Zheng <lv.zheng@intel.com>
> +=========================================================
> +Special Usage Model of the ACPI Control Method Lid Device
> +=========================================================
>  
> +:Copyright: |copy| 2016, Intel Corporation
>  
> -Abstract:
> +:Author: Lv Zheng <lv.zheng@intel.com>
>  
> -Platforms containing lids convey lid state (open/close) to OSPMs using a
> -control method lid device. To implement this, the AML tables issue
> -Notify(lid_device, 0x80) to notify the OSPMs whenever the lid state has
> -changed. The _LID control method for the lid device must be implemented to
> -report the "current" state of the lid as either "opened" or "closed".
> +:Abstract: Platforms containing lids convey lid state (open/close) to OSPMs
> +  using a control method lid device. To implement this, the AML tables issue
> +  Notify(lid_device, 0x80) to notify the OSPMs whenever the lid state has
> +  changed. The _LID control method for the lid device must be implemented to
> +  report the "current" state of the lid as either "opened" or "closed".

Same comment for the abstract.
>  
> -For most platforms, both the _LID method and the lid notifications are
> -reliable. However, there are exceptions. In order to work with these
> -exceptional buggy platforms, special restrictions and expections should be
> -taken into account. This document describes the restrictions and the
> -expections of the Linux ACPI lid device driver.
> +  For most platforms, both the _LID method and the lid notifications are
> +  reliable. However, there are exceptions. In order to work with these
> +  exceptional buggy platforms, special restrictions and expections should be
> +  taken into account. This document describes the restrictions and the
> +  expections of the Linux ACPI lid device driver.
>  
>  
>  1. Restrictions of the returning value of the _LID control method
> +=================================================================
>  
>  The _LID control method is described to return the "current" lid state.
>  However the word of "current" has ambiguity, some buggy AML tables return
> @@ -31,6 +35,7 @@ with cached value, the initial returning value is likely not reliable.
>  There are platforms always retun "closed" as initial lid state.
>  
>  2. Restrictions of the lid state change notifications
> +=====================================================
>  
>  There are buggy AML tables never notifying when the lid device state is
>  changed to "opened". Thus the "opened" notification is not guaranteed. But
> @@ -40,17 +45,21 @@ trigger some system power saving operations on Windows. Since it is fully
>  tested, it is reliable from all AML tables.
>  
>  3. Expections for the userspace users of the ACPI lid device driver
> +===================================================================
>  
>  The ACPI button driver exports the lid state to the userspace via the
> -following file:
> +following file::
> +
>    /proc/acpi/button/lid/LID0/state
> +
>  This file actually calls the _LID control method described above. And given
>  the previous explanation, it is not reliable enough on some platforms. So
>  it is advised for the userspace program to not to solely rely on this file
>  to determine the actual lid state.
>  
>  The ACPI button driver emits the following input event to the userspace:
> -  SW_LID
> +  * SW_LID
> +
>  The ACPI lid device driver is implemented to try to deliver the platform
>  triggered events to the userspace. However, given the fact that the buggy
>  firmware cannot make sure "opened"/"closed" events are paired, the ACPI
> @@ -59,20 +68,25 @@ button driver uses the following 3 modes in order not to trigger issues.
>  If the userspace hasn't been prepared to ignore the unreliable "opened"
>  events and the unreliable initial state notification, Linux users can use
>  the following kernel parameters to handle the possible issues:
> +
>  A. button.lid_init_state=method:

Just for the sake of a better visual at the html output, I would place those
button.* as:

  A. ``button.lid_init_state=method``:

Anyway, with or without such change:

Reviewed-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

>     When this option is specified, the ACPI button driver reports the
>     initial lid state using the returning value of the _LID control method
>     and whether the "opened"/"closed" events are paired fully relies on the
>     firmware implementation.
> +
>     This option can be used to fix some platforms where the returning value
>     of the _LID control method is reliable but the initial lid state
>     notification is missing.
> +
>     This option is the default behavior during the period the userspace
>     isn't ready to handle the buggy AML tables.
> +
>  B. button.lid_init_state=open:
>     When this option is specified, the ACPI button driver always reports the
>     initial lid state as "opened" and whether the "opened"/"closed" events
>     are paired fully relies on the firmware implementation.
> +
>     This may fix some platforms where the returning value of the _LID
>     control method is not reliable and the initial lid state notification is
>     missing.
> @@ -80,6 +94,7 @@ B. button.lid_init_state=open:
>  If the userspace has been prepared to ignore the unreliable "opened" events
>  and the unreliable initial state notification, Linux users should always
>  use the following kernel parameter:
> +
>  C. button.lid_init_state=ignore:
>     When this option is specified, the ACPI button driver never reports the
>     initial lid state and there is a compensation mechanism implemented to
> @@ -89,6 +104,7 @@ C. button.lid_init_state=ignore:
>     notifications can be delivered to the userspace when the lid is actually
>     opens given that some AML tables do not send "opened" notifications
>     reliably.
> +
>     In this mode, if everything is correctly implemented by the platform
>     firmware, the old userspace programs should still work. Otherwise, the
>     new userspace programs are required to work with the ACPI button driver.
> diff --git a/Documentation/firmware-guide/acpi/index.rst b/Documentation/firmware-guide/acpi/index.rst
> index 1c89888f6ee8..bedcb0b242a2 100644
> --- a/Documentation/firmware-guide/acpi/index.rst
> +++ b/Documentation/firmware-guide/acpi/index.rst
> @@ -14,3 +14,4 @@ ACPI Support
>     DSD-properties-rules
>     gpio-properties
>     i2c-muxes
> +   acpi-lid
> \ No newline at end of file


Thanks,
Mauro