| 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 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 |
| |
| 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 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 |
| <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 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 |
| |
| 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 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. |
| |
| 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 |
