ACPI: Add documentation describing ACPICA release automation (9305aa6f) · Commits · e / devices / android_kernel_fairphone_FP3

Documentation/acpi/linuxized-acpica.txt

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		Linuxized ACPICA - Introduction to ACPICA Release Automation

		Copyright (C) 2013-2016, Intel Corporation
		Author: Lv Zheng <lv.zheng@intel.com>


		Abstract:

		This document describes the ACPICA project and the relationship between
		ACPICA and Linux. It also describes how ACPICA code in drivers/acpi/acpica,
		include/acpi and tools/power/acpi is automatically updated to follow the
		upstream.


		1. ACPICA Project

		The ACPI Component Architecture (ACPICA) project provides an operating
		system (OS)-independent reference implementation of the Advanced
		Configuration and Power Interface Specification (ACPI). It has been
		adapted by various host OSes. By directly integrating ACPICA, Linux can
		also benefit from the application experiences of ACPICA from other host
		OSes.

		The homepage of ACPICA project is: www.acpica.org, it is maintained and
		supported by Intel Corporation.

		The following figure depicts the Linux ACPI subystem where the ACPICA
		adaptation is included:

		+---------------------------------------------------------+
		\| \|
		\| +---------------------------------------------------+ \|
		\| \| +------------------+ \| \|
		\| \| \| Table Management \| \| \|
		\| \| +------------------+ \| \|
		\| \| +----------------------+ \| \|
		\| \| \| Namespace Management \| \| \|
		\| \| +----------------------+ \| \|
		\| \| +------------------+ ACPICA Components \| \|
		\| \| \| Event Management \| \| \|
		\| \| +------------------+ \| \|
		\| \| +---------------------+ \| \|
		\| \| \| Resource Management \| \| \|
		\| \| +---------------------+ \| \|
		\| \| +---------------------+ \| \|
		\| \| \| Hardware Management \| \| \|
		\| \| +---------------------+ \| \|
		\| +---------------------------------------------------+ \| \|
		\| \| \| +------------------+ \| \| \|
		\| \| \| \| OS Service Layer \| \| \| \|
		\| \| \| +------------------+ \| \| \|
		\| \| +-------------------------------------------------\|-+ \|
		\| \| +--------------------+ \| \|
		\| \| \| Device Enumeration \| \| \|
		\| \| +--------------------+ \| \|
		\| \| +------------------+ \| \|
		\| \| \| Power Management \| \| \|
		\| \| +------------------+ Linux/ACPI Components \| \|
		\| \| +--------------------+ \| \|
		\| \| \| Thermal Management \| \| \|
		\| \| +--------------------+ \| \|
		\| \| +--------------------------+ \| \|
		\| \| \| Drivers for ACPI Devices \| \| \|
		\| \| +--------------------------+ \| \|
		\| \| +--------+ \| \|
		\| \| \| ...... \| \| \|
		\| \| +--------+ \| \|
		\| +---------------------------------------------------+ \|
		\| \|
		+---------------------------------------------------------+

		Figure 1. Linux ACPI Software Components

		NOTE:
		A. OS Service Layer - Provided by Linux to offer OS dependent
		implementation of the predefined ACPICA interfaces (acpi_os_*).
		include/acpi/acpiosxf.h
		drivers/acpi/osl.c
		include/acpi/platform
		include/asm/acenv.h
		B. ACPICA Functionality - Released from ACPICA code base to offer
		OS independent implementation of the ACPICA interfaces (acpi_*).
		drivers/acpi/acpica
		include/acpi/ac*.h
		tools/power/acpi
		C. Linux/ACPI Functionality - Providing Linux specific ACPI
		functionality to the other Linux kernel subsystems and user space
		programs.
		drivers/acpi
		include/linux/acpi.h
		include/linux/acpi*.h
		include/acpi
		tools/power/acpi
		D. Architecture Specific ACPICA/ACPI Functionalities - Provided by the
		ACPI subsystem to offer architecture specific implementation of the
		ACPI interfaces. They are Linux specific components and are out of
		the scope of this document.
		include/asm/acpi.h
		include/asm/acpi*.h
		arch/*/acpi

		2. ACPICA Release

		The ACPICA project maintains its code base at the following repository URL:
		https://github.com/acpica/acpica.git. As a rule, a release is made every
		month.

		As the coding style adopted by the ACPICA project is not acceptable by
		Linux, there is a release process to convert the ACPICA git commits into
		Linux patches. The patches generated by this process are referred to as
		"linuxized ACPICA patches". The release process is carried out on a local
		copy the ACPICA git repository. Each commit in the monthly release is
		converted into a linuxized ACPICA patch. Together, they form the montly
		ACPICA release patchset for the Linux ACPI community. This process is
		illustrated in the following figure:

		+-----------------------------+
		\| acpica / master (-) commits \|
		+-----------------------------+
		/\|\ \|
		\| \\|/
		\| /---------------------\ +----------------------+
		\| < Linuxize repo Utility >-->\| old linuxized acpica \|--+
		\| \---------------------/ +----------------------+ \|
		\| \|
		/---------\ \|
		< git reset > \
		\---------/ \
		/\|\ /+-+
		\| / \|
		+-----------------------------+ \| \|
		\| acpica / master (+) commits \| \| \|
		+-----------------------------+ \| \|
		\| \| \|
		\\|/ \| \|
		/-----------------------\ +----------------------+ \| \|
		< Linuxize repo Utilities >-->\| new linuxized acpica \|--+ \|
		\-----------------------/ +----------------------+ \|
		\\|/
		+--------------------------+ /----------------------\
		\| Linuxized ACPICA Patches \|<----------------< Linuxize patch Utility >
		+--------------------------+ \----------------------/
		\|
		\\|/
		/---------------------------\
		< Linux ACPI Community Review >
		\---------------------------/
		\|
		\\|/
		+-----------------------+ /------------------\ +----------------+
		\| linux-pm / linux-next \|-->< Linux Merge Window >-->\| linux / master \|
		+-----------------------+ \------------------/ +----------------+

		Figure 2. ACPICA -> Linux Upstream Process

		NOTE:
		A. Linuxize Utilities - Provided by the ACPICA repository, including a
		utility located in source/tools/acpisrc folder and a number of
		scripts located in generate/linux folder.
		B. acpica / master - "master" branch of the git repository at
		<https://github.com/acpica/acpica.git>.
		C. linux-pm / linux-next - "linux-next" branch of the git repository at
		<http://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git>.
		D. linux / master - "master" branch of the git repository at
		<http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git>.

		Before the linuxized ACPICA patches are sent to the Linux ACPI community
		for review, there is a quality ensurance build test process to reduce
		porting issues. Currently this build process only takes care of the
		following kernel configuration options:
		CONFIG_ACPI/CONFIG_ACPI_DEBUG/CONFIG_ACPI_DEBUGGER

		3. ACPICA Divergences

		Ideally, all of the ACPICA commits should be converted into Linux patches
		automatically without manual modifications, the "linux / master" tree should
		contain the ACPICA code that exactly corresponds to the ACPICA code
		contained in "new linuxized acpica" tree and it should be possible to run
		the release process fully automatically.

		As a matter of fact, however, there are source code differences between
		the ACPICA code in Linux and the upstream ACPICA code, referred to as
		"ACPICA Divergences".

		The various sources of ACPICA divergences include:
		1. Legacy divergences - Before the current ACPICA release process was
		established, there already had been divergences between Linux and
		ACPICA. Over the past several years those divergences have been greatly
		reduced, but there still are several ones and it takes time to figure
		out the underlying reasons for their existence.
		2. Manual modifications - Any manual modification (eg. coding style fixes)
		made directly in the Linux sources obviously hurts the ACPICA release
		automation. Thus it is recommended to fix such issues in the ACPICA
		upstream source code and generate the linuxized fix using the ACPICA
		release utilities (please refer to Section 4 below for the details).
		3. Linux specific features - Sometimes it's impossible to use the
		current ACPICA APIs to implement features required by the Linux kernel,
		so Linux developers occasionaly have to change ACPICA code directly.
		Those changes may not be acceptable by ACPICA upstream and in such cases
		they are left as committed ACPICA divergences unless the ACPICA side can
		implement new mechanisms as replacements for them.
		4. ACPICA release fixups - ACPICA only tests commits using a set of the
		user space simulation utilies, thus the linuxized ACPICA patches may
		break the Linux kernel, leaving us build/boot failures. In order to
		avoid breaking Linux bisection, fixes are applied directly to the
		linuxized ACPICA patches during the release process. When the release
		fixups are backported to the upstream ACPICA sources, they must follow
		the upstream ACPICA rules and so further modifications may appear.
		That may result in the appearance of new divergences.
		5. Fast tracking of ACPICA commits - Some ACPICA commits are regression
		fixes or stable-candidate material, so they are applied in advance with
		respect to the ACPICA release process. If such commits are reverted or
		rebased on the ACPICA side in order to offer better solutions, new ACPICA
		divergences are generated.

		4. ACPICA Development

		This paragraph guides Linux developers to use the ACPICA upstream release
		utilities to obtain Linux patches corresponding to upstream ACPICA commits
		before they become available from the ACPICA release process.

		1. Cherry-pick an ACPICA commit

		First you need to git clone the ACPICA repository and the ACPICA change
		you want to cherry pick must be committed into the local repository.

		Then the gen-patch.sh command can help to cherry-pick an ACPICA commit
		from the ACPICA local repository:

		$ git clone https://github.com/acpica/acpica
		$ cd acpica
		$ generate/linux/gen-patch.sh -u [commit ID]

		Here the commit ID is the ACPICA local repository commit ID you want to
		cherry pick. It can be omitted if the commit is "HEAD".

		2. Cherry-pick recent ACPICA commits

		Sometimes you need to rebase your code on top of the most recent ACPICA
		changes that haven't been applied to Linux yet.

		You can generate the ACPICA release series yourself and rebase your code on
		top of the generated ACPICA release patches:

		$ git clone https://github.com/acpica/acpica
		$ cd acpica
		$ generate/linux/make-patches.sh -u [commit ID]

		The commit ID should be the last ACPICA commit accepted by Linux. Usually,
		it is the commit modifying ACPI_CA_VERSION. It can be found by executing
		"git blame source/include/acpixf.h" and referencing the line that contains
		"ACPI_CA_VERSION".

		3. Inspect the current divergences

		If you have local copies of both Linux and upstream ACPICA, you can generate
		a diff file indicating the state of the current divergences:

		# git clone https://github.com/acpica/acpica
		# git clone http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
		# cd acpica
		# generate/linux/divergences.sh -s ../linux