linux/Documentation/ABI
Linus Torvalds 355ba37d75 Power management updates for 5.8-rc1
- Rework the system-wide PM driver flags to make them easier to
    understand and use and update their documentation (Rafael Wysocki,
    Alan Stern).
 
  - Allow cpuidle governors to be switched at run time regardless of
    the kernel configuration and update the related documentation
    accordingly (Hanjun Guo).
 
  - Improve the resume device handling in the user space hibernarion
    interface code (Domenico Andreoli).
 
  - Document the intel-speed-select sysfs interface (Srinivas
    Pandruvada).
 
  - Make the ACPI code handing suspend to idle print more debug
    messages to help diagnose issues with it (Rafael Wysocki).
 
  - Fix a helper routine in the cpufreq core and correct a typo in
    the struct cpufreq_driver kerneldoc comment (Rafael Wysocki, Wang
    Wenhu).
 
  - Update cpufreq drivers:
 
    * Make the intel_pstate driver start in the passive mode by
      default on systems without HWP (Rafael Wysocki).
 
    * Add i.MX7ULP support to the imx-cpufreq-dt driver and add
      i.MX7ULP to the cpufreq-dt-platdev blacklist (Peng Fan).
 
    * Convert the qoriq cpufreq driver to a platform one, make the
      platform code create a suitable device object for it and add
      platform dependencies to it (Mian Yousaf Kaukab, Geert
      Uytterhoeven).
 
    * Fix wrong compatible binding in the qcom driver (Ansuel Smith).
 
    * Build the omap driver by default for ARCH_OMAP2PLUS (Anders
      Roxell).
 
    * Add r8a7742 SoC support to the dt cpufreq driver (Lad Prabhakar).
 
  - Update cpuidle core and drivers:
 
    * Fix three reference count leaks in error code paths in the
      cpuidle core (Qiushi Wu).
 
    * Convert Qualcomm SPM to a generic cpuidle driver (Stephan
      Gerhold).
 
    * Fix up the execution order when entering a domain idle state in
      the PSCI driver (Ulf Hansson).
 
  - Fix a reference counting issue related to clock management and
    clean up two oddities in the PM-runtime framework (Rafael Wysocki,
    Andy Shevchenko).
 
  - Add ElkhartLake support to the Intel RAPL power capping driver
    and remove an unused local MSR definition from it (Jacob Pan,
    Sumeet Pawnikar).
 
  - Update devfreq core and drivers:
 
    * Replace strncpy() with strscpy() in the devfreq core and use
      lockdep asserts instead of manual checks for a locked mutex in
      it (Dmitry Osipenko, Krzysztof Kozlowski).
 
    * Add a generic imx bus scaling driver and make it register an
      interconnect device (Leonard Crestez, Gustavo A. R. Silva).
 
    * Make the cpufreq notifier in the tegra30 driver take boosting
      into account and delete an unuseful error message from that
      driver (Dmitry Osipenko, Markus Elfring).
 
  - Remove unneeded semicolon from the cpupower code (Zou Wei).
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Merge tag 'pm-5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm

Pull power management updates from Rafael Wysocki:
 "These rework the system-wide PM driver flags, make runtime switching
  of cpuidle governors easier, improve the user space hibernation
  interface code, add intel-speed-select interface documentation, add
  more debug messages to the ACPI code handling suspend to idle, update
  the cpufreq core and drivers, fix a minor issue in the cpuidle core
  and update two cpuidle drivers, improve the PM-runtime framework,
  update the Intel RAPL power capping driver, update devfreq core and
  drivers, and clean up the cpupower utility.

  Specifics:

   - Rework the system-wide PM driver flags to make them easier to
     understand and use and update their documentation (Rafael Wysocki,
     Alan Stern).

   - Allow cpuidle governors to be switched at run time regardless of
     the kernel configuration and update the related documentation
     accordingly (Hanjun Guo).

   - Improve the resume device handling in the user space hibernarion
     interface code (Domenico Andreoli).

   - Document the intel-speed-select sysfs interface (Srinivas
     Pandruvada).

   - Make the ACPI code handing suspend to idle print more debug
     messages to help diagnose issues with it (Rafael Wysocki).

   - Fix a helper routine in the cpufreq core and correct a typo in the
     struct cpufreq_driver kerneldoc comment (Rafael Wysocki, Wang
     Wenhu).

   - Update cpufreq drivers:

      - Make the intel_pstate driver start in the passive mode by
        default on systems without HWP (Rafael Wysocki).

      - Add i.MX7ULP support to the imx-cpufreq-dt driver and add
        i.MX7ULP to the cpufreq-dt-platdev blacklist (Peng Fan).

      - Convert the qoriq cpufreq driver to a platform one, make the
        platform code create a suitable device object for it and add
        platform dependencies to it (Mian Yousaf Kaukab, Geert
        Uytterhoeven).

      - Fix wrong compatible binding in the qcom driver (Ansuel Smith).

      - Build the omap driver by default for ARCH_OMAP2PLUS (Anders
        Roxell).

      - Add r8a7742 SoC support to the dt cpufreq driver (Lad
        Prabhakar).

   - Update cpuidle core and drivers:

      - Fix three reference count leaks in error code paths in the
        cpuidle core (Qiushi Wu).

      - Convert Qualcomm SPM to a generic cpuidle driver (Stephan
        Gerhold).

      - Fix up the execution order when entering a domain idle state in
        the PSCI driver (Ulf Hansson).

   - Fix a reference counting issue related to clock management and
     clean up two oddities in the PM-runtime framework (Rafael Wysocki,
     Andy Shevchenko).

   - Add ElkhartLake support to the Intel RAPL power capping driver and
     remove an unused local MSR definition from it (Jacob Pan, Sumeet
     Pawnikar).

   - Update devfreq core and drivers:

      - Replace strncpy() with strscpy() in the devfreq core and use
        lockdep asserts instead of manual checks for a locked mutex in
        it (Dmitry Osipenko, Krzysztof Kozlowski).

      - Add a generic imx bus scaling driver and make it register an
        interconnect device (Leonard Crestez, Gustavo A. R. Silva).

      - Make the cpufreq notifier in the tegra30 driver take boosting
        into account and delete an unuseful error message from that
        driver (Dmitry Osipenko, Markus Elfring).

   - Remove unneeded semicolon from the cpupower code (Zou Wei)"

* tag 'pm-5.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: (51 commits)
  cpuidle: Fix three reference count leaks
  PM: runtime: Replace pm_runtime_callbacks_present()
  PM / devfreq: Use lockdep asserts instead of manual checks for locked mutex
  PM / devfreq: imx-bus: Fix inconsistent IS_ERR and PTR_ERR
  PM / devfreq: Replace strncpy with strscpy
  PM / devfreq: imx: Register interconnect device
  PM / devfreq: Add generic imx bus scaling driver
  PM / devfreq: tegra30: Delete an error message in tegra_devfreq_probe()
  PM / devfreq: tegra30: Make CPUFreq notifier to take into account boosting
  PM: hibernate: Restrict writes to the resume device
  PM: runtime: clk: Fix clk_pm_runtime_get() error path
  cpuidle: Convert Qualcomm SPM driver to a generic CPUidle driver
  ACPI: EC: PM: s2idle: Extend GPE dispatching debug message
  ACPI: PM: s2idle: Print type of wakeup debug messages
  powercap: RAPL: remove unused local MSR define
  PM: runtime: Make clear what we do when conditions are wrong in rpm_suspend()
  Documentation: admin-guide: pm: Document intel-speed-select
  PM: hibernate: Split off snapshot dev option
  PM: hibernate: Incorporate concurrency handling
  Documentation: ABI: make current_governer_ro as a candidate for removal
  ...
2020-06-02 13:17:23 -07:00
..
obsolete Power management updates for 5.8-rc1 2020-06-02 13:17:23 -07:00
removed powerpc updates for 5.7 2020-04-05 11:12:59 -07:00
stable docs: filesystems: fix renamed references 2020-04-20 15:45:22 -06:00
testing Power management updates for 5.8-rc1 2020-06-02 13:17:23 -07:00
README docs: fix locations of several documents that got moved 2016-10-24 08:12:35 -02:00

This directory attempts to document the ABI between the Linux kernel and
userspace, and the relative stability of these interfaces.  Due to the
everchanging nature of Linux, and the differing maturity levels, these
interfaces should be used by userspace programs in different ways.

We have four different levels of ABI stability, as shown by the four
different subdirectories in this location.  Interfaces may change levels
of stability according to the rules described below.

The different levels of stability are:

  stable/
	This directory documents the interfaces that the developer has
	defined to be stable.  Userspace programs are free to use these
	interfaces with no restrictions, and backward compatibility for
	them will be guaranteed for at least 2 years.  Most interfaces
	(like syscalls) are expected to never change and always be
	available.

  testing/
	This directory documents interfaces that are felt to be stable,
	as the main development of this interface has been completed.
	The interface can be changed to add new features, but the
	current interface will not break by doing this, unless grave
	errors or security problems are found in them.  Userspace
	programs can start to rely on these interfaces, but they must be
	aware of changes that can occur before these interfaces move to
	be marked stable.  Programs that use these interfaces are
	strongly encouraged to add their name to the description of
	these interfaces, so that the kernel developers can easily
	notify them if any changes occur (see the description of the
	layout of the files below for details on how to do this.)

  obsolete/
  	This directory documents interfaces that are still remaining in
	the kernel, but are marked to be removed at some later point in
	time.  The description of the interface will document the reason
	why it is obsolete and when it can be expected to be removed.

  removed/
	This directory contains a list of the old interfaces that have
	been removed from the kernel.

Every file in these directories will contain the following information:

What:		Short description of the interface
Date:		Date created
KernelVersion:	Kernel version this feature first showed up in.
Contact:	Primary contact for this interface (may be a mailing list)
Description:	Long description of the interface and how to use it.
Users:		All users of this interface who wish to be notified when
		it changes.  This is very important for interfaces in
		the "testing" stage, so that kernel developers can work
		with userspace developers to ensure that things do not
		break in ways that are unacceptable.  It is also
		important to get feedback for these interfaces to make
		sure they are working in a proper way and do not need to
		be changed further.


How things move between levels:

Interfaces in stable may move to obsolete, as long as the proper
notification is given.

Interfaces may be removed from obsolete and the kernel as long as the
documented amount of time has gone by.

Interfaces in the testing state can move to the stable state when the
developers feel they are finished.  They cannot be removed from the
kernel tree without going through the obsolete state first.

It's up to the developer to place their interfaces in the category they
wish for it to start out in.


Notable bits of non-ABI, which should not under any circumstances be considered
stable:

- Kconfig.  Userspace should not rely on the presence or absence of any
  particular Kconfig symbol, in /proc/config.gz, in the copy of .config
  commonly installed to /boot, or in any invocation of the kernel build
  process.

- Kernel-internal symbols.  Do not rely on the presence, absence, location, or
  type of any kernel symbol, either in System.map files or the kernel binary
  itself.  See Documentation/process/stable-api-nonsense.rst.