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1 Linuxized ACPICA - Introduction to ACPICA Release Automation
3 Copyright (C) 2013-2016, Intel Corporation
4 Author: Lv Zheng <lv.zheng@intel.com>
7 Abstract:
9 This document describes the ACPICA project and the relationship between
10 ACPICA and Linux. It also describes how ACPICA code in drivers/acpi/acpica,
11 include/acpi and tools/power/acpi is automatically updated to follow the
12 upstream.
15 1. ACPICA Project
17 The ACPI Component Architecture (ACPICA) project provides an operating
18 system (OS)-independent reference implementation of the Advanced
19 Configuration and Power Interface Specification (ACPI). It has been
20 adapted by various host OSes. By directly integrating ACPICA, Linux can
21 also benefit from the application experiences of ACPICA from other host
22 OSes.
24 The homepage of ACPICA project is: www.acpica.org, it is maintained and
25 supported by Intel Corporation.
27 The following figure depicts the Linux ACPI subystem where the ACPICA
28 adaptation is included:
30 +---------------------------------------------------------+
31 | |
32 | +---------------------------------------------------+ |
33 | | +------------------+ | |
34 | | | Table Management | | |
35 | | +------------------+ | |
36 | | +----------------------+ | |
37 | | | Namespace Management | | |
38 | | +----------------------+ | |
39 | | +------------------+ ACPICA Components | |
40 | | | Event Management | | |
41 | | +------------------+ | |
42 | | +---------------------+ | |
43 | | | Resource Management | | |
44 | | +---------------------+ | |
45 | | +---------------------+ | |
46 | | | Hardware Management | | |
47 | | +---------------------+ | |
48 | +---------------------------------------------------+ | |
49 | | | +------------------+ | | |
50 | | | | OS Service Layer | | | |
51 | | | +------------------+ | | |
52 | | +-------------------------------------------------|-+ |
53 | | +--------------------+ | |
54 | | | Device Enumeration | | |
55 | | +--------------------+ | |
56 | | +------------------+ | |
57 | | | Power Management | | |
58 | | +------------------+ Linux/ACPI Components | |
59 | | +--------------------+ | |
60 | | | Thermal Management | | |
61 | | +--------------------+ | |
62 | | +--------------------------+ | |
63 | | | Drivers for ACPI Devices | | |
64 | | +--------------------------+ | |
65 | | +--------+ | |
66 | | | ...... | | |
67 | | +--------+ | |
68 | +---------------------------------------------------+ |
69 | |
70 +---------------------------------------------------------+
72 Figure 1. Linux ACPI Software Components
74 NOTE:
75 A. OS Service Layer - Provided by Linux to offer OS dependent
76 implementation of the predefined ACPICA interfaces (acpi_os_*).
77 include/acpi/acpiosxf.h
78 drivers/acpi/osl.c
79 include/acpi/platform
80 include/asm/acenv.h
81 B. ACPICA Functionality - Released from ACPICA code base to offer
82 OS independent implementation of the ACPICA interfaces (acpi_*).
83 drivers/acpi/acpica
84 include/acpi/ac*.h
85 tools/power/acpi
86 C. Linux/ACPI Functionality - Providing Linux specific ACPI
87 functionality to the other Linux kernel subsystems and user space
88 programs.
89 drivers/acpi
90 include/linux/acpi.h
91 include/linux/acpi*.h
92 include/acpi
93 tools/power/acpi
94 D. Architecture Specific ACPICA/ACPI Functionalities - Provided by the
95 ACPI subsystem to offer architecture specific implementation of the
96 ACPI interfaces. They are Linux specific components and are out of
97 the scope of this document.
98 include/asm/acpi.h
99 include/asm/acpi*.h
100 arch/*/acpi
102 2. ACPICA Release
104 The ACPICA project maintains its code base at the following repository URL:
105 https://github.com/acpica/acpica.git. As a rule, a release is made every
106 month.
108 As the coding style adopted by the ACPICA project is not acceptable by
109 Linux, there is a release process to convert the ACPICA git commits into
110 Linux patches. The patches generated by this process are referred to as
111 "linuxized ACPICA patches". The release process is carried out on a local
112 copy the ACPICA git repository. Each commit in the monthly release is
113 converted into a linuxized ACPICA patch. Together, they form the montly
114 ACPICA release patchset for the Linux ACPI community. This process is
115 illustrated in the following figure:
117 +-----------------------------+
118 | acpica / master (-) commits |
119 +-----------------------------+
120 /|\ |
121 | \|/
122 | /---------------------\ +----------------------+
123 | < Linuxize repo Utility >-->| old linuxized acpica |--+
124 | \---------------------/ +----------------------+ |
125 | |
126 /---------\ |
127 < git reset > \
128 \---------/ \
129 /|\ /+-+
130 | / |
131 +-----------------------------+ | |
132 | acpica / master (+) commits | | |
133 +-----------------------------+ | |
134 | | |
135 \|/ | |
136 /-----------------------\ +----------------------+ | |
137 < Linuxize repo Utilities >-->| new linuxized acpica |--+ |
138 \-----------------------/ +----------------------+ |
139 \|/
140 +--------------------------+ /----------------------\
141 | Linuxized ACPICA Patches |<----------------< Linuxize patch Utility >
142 +--------------------------+ \----------------------/
143 |
144 \|/
145 /---------------------------\
146 < Linux ACPI Community Review >
147 \---------------------------/
148 |
149 \|/
150 +-----------------------+ /------------------\ +----------------+
151 | linux-pm / linux-next |-->< Linux Merge Window >-->| linux / master |
152 +-----------------------+ \------------------/ +----------------+
154 Figure 2. ACPICA -> Linux Upstream Process
156 NOTE:
157 A. Linuxize Utilities - Provided by the ACPICA repository, including a
158 utility located in source/tools/acpisrc folder and a number of
159 scripts located in generate/linux folder.
160 B. acpica / master - "master" branch of the git repository at
161 <https://github.com/acpica/acpica.git>.
162 C. linux-pm / linux-next - "linux-next" branch of the git repository at
163 <http://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git>.
164 D. linux / master - "master" branch of the git repository at
165 <http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git>.
167 Before the linuxized ACPICA patches are sent to the Linux ACPI community
168 for review, there is a quality ensurance build test process to reduce
169 porting issues. Currently this build process only takes care of the
170 following kernel configuration options:
171 CONFIG_ACPI/CONFIG_ACPI_DEBUG/CONFIG_ACPI_DEBUGGER
173 3. ACPICA Divergences
175 Ideally, all of the ACPICA commits should be converted into Linux patches
176 automatically without manual modifications, the "linux / master" tree should
177 contain the ACPICA code that exactly corresponds to the ACPICA code
178 contained in "new linuxized acpica" tree and it should be possible to run
179 the release process fully automatically.
181 As a matter of fact, however, there are source code differences between
182 the ACPICA code in Linux and the upstream ACPICA code, referred to as
183 "ACPICA Divergences".
185 The various sources of ACPICA divergences include:
186 1. Legacy divergences - Before the current ACPICA release process was
187 established, there already had been divergences between Linux and
188 ACPICA. Over the past several years those divergences have been greatly
189 reduced, but there still are several ones and it takes time to figure
190 out the underlying reasons for their existence.
191 2. Manual modifications - Any manual modification (eg. coding style fixes)
192 made directly in the Linux sources obviously hurts the ACPICA release
193 automation. Thus it is recommended to fix such issues in the ACPICA
194 upstream source code and generate the linuxized fix using the ACPICA
195 release utilities (please refer to Section 4 below for the details).
196 3. Linux specific features - Sometimes it's impossible to use the
197 current ACPICA APIs to implement features required by the Linux kernel,
198 so Linux developers occasionaly have to change ACPICA code directly.
199 Those changes may not be acceptable by ACPICA upstream and in such cases
200 they are left as committed ACPICA divergences unless the ACPICA side can
201 implement new mechanisms as replacements for them.
202 4. ACPICA release fixups - ACPICA only tests commits using a set of the
203 user space simulation utilies, thus the linuxized ACPICA patches may
204 break the Linux kernel, leaving us build/boot failures. In order to
205 avoid breaking Linux bisection, fixes are applied directly to the
206 linuxized ACPICA patches during the release process. When the release
207 fixups are backported to the upstream ACPICA sources, they must follow
208 the upstream ACPICA rules and so further modifications may appear.
209 That may result in the appearance of new divergences.
210 5. Fast tracking of ACPICA commits - Some ACPICA commits are regression
211 fixes or stable-candidate material, so they are applied in advance with
212 respect to the ACPICA release process. If such commits are reverted or
213 rebased on the ACPICA side in order to offer better solutions, new ACPICA
214 divergences are generated.
216 4. ACPICA Development
218 This paragraph guides Linux developers to use the ACPICA upstream release
219 utilities to obtain Linux patches corresponding to upstream ACPICA commits
220 before they become available from the ACPICA release process.
222 1. Cherry-pick an ACPICA commit
224 First you need to git clone the ACPICA repository and the ACPICA change
225 you want to cherry pick must be committed into the local repository.
227 Then the gen-patch.sh command can help to cherry-pick an ACPICA commit
228 from the ACPICA local repository:
230 $ git clone https://github.com/acpica/acpica
231 $ cd acpica
232 $ generate/linux/gen-patch.sh -u [commit ID]
234 Here the commit ID is the ACPICA local repository commit ID you want to
235 cherry pick. It can be omitted if the commit is "HEAD".
237 2. Cherry-pick recent ACPICA commits
239 Sometimes you need to rebase your code on top of the most recent ACPICA
240 changes that haven't been applied to Linux yet.
242 You can generate the ACPICA release series yourself and rebase your code on
243 top of the generated ACPICA release patches:
245 $ git clone https://github.com/acpica/acpica
246 $ cd acpica
247 $ generate/linux/make-patches.sh -u [commit ID]
249 The commit ID should be the last ACPICA commit accepted by Linux. Usually,
250 it is the commit modifying ACPI_CA_VERSION. It can be found by executing
251 "git blame source/include/acpixf.h" and referencing the line that contains
252 "ACPI_CA_VERSION".
254 3. Inspect the current divergences
256 If you have local copies of both Linux and upstream ACPICA, you can generate
257 a diff file indicating the state of the current divergences:
259 # git clone https://github.com/acpica/acpica
260 # git clone http://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
261 # cd acpica
262 # generate/linux/divergences.sh -s ../linux