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diff --git a/Documentation/driver-api/acpi/linuxized-acpica.rst b/Documentation/driver-api/acpi/linuxized-acpica.rst new file mode 100644 index 000000000..cc234353d --- /dev/null +++ b/Documentation/driver-api/acpi/linuxized-acpica.rst @@ -0,0 +1,279 @@ +.. SPDX-License-Identifier: GPL-2.0 +.. include:: <isonum.txt> + +============================================================ +Linuxized ACPICA - Introduction to ACPICA Release Automation +============================================================ + +:Copyright: |copy| 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. + +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 subsystem 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 + +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 monthly +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 + <https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git>. + D. linux / master - "master" branch of the git repository at + <https://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 assurance 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 + +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 occasionally 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 utilities, 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. + +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 https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git + # cd acpica + # generate/linux/divergence.sh -s ../linux |