[SRU][P/O/N][PATCH v2 0/3] Introduce configfs-based interface for gpio-aggregator (LP: #2103496)

Tue Apr 15 06:13:18 UTC 2025

BugLink: https://bugs.launchpad.net/bugs/2103496

[ Impact ]

The existing 'new_device' interface for gpio-aggregator
(https://docs.kernel.org/admin-guide/gpio/gpio-aggregator.html) has several
limitations:

  * No way to determine when GPIO aggregator creation is complete.
  * No way to retrieve errors when creating a GPIO aggregator.
  * No way to trace a GPIO line of an aggregator back to its corresponding
    physical device.
  * The 'new_device' echo does not indicate which virtual gpiochip<N> was
    created.
  * No way to assign names to GPIO lines exported through an aggregator.

While the GPIO aggregator concept is useful for resource isolation, these
limitations currently hinder its practical effectiveness. This patch series
addresses all those issues.

[ Fix ]

For Plucky, I cherry-picked the v6 patch series [1] to include it in the
Release before the main patch series reached linux-next. See the APPLIED
announcement [2]. As a result, the code differs slightly from the v7 patch
series [3], which later made it to linux-next and was used for backporting
to Oracular/Noble as explained below. However, since there are no
substantial differences between v6 and v7, I do not intend to modify Plucky
to match v7.

For Plucky, apply 18 patches in total:

  * Already applied 12 patches below via [2].
    -  Applied [PATCH 1/3] to [PATCH 3/3] from [4], which had landed in
       linux-next.
    -  Applied [PATCH 2/9] to [PATCH 9/9] from [1], which had been under
       review.
    -  Added a "UBUNTU: [Config]" commit for the new config option
       CONFIG_DEV_SYNC_PROBE.
    Note:
    * [4] is a preparatory patch series for [1].
    * [PATCH 1/9] from [1] was already picked and landed in mainline.

  * Cherry-pick 6 commits (follow-up fixes) from gpio/for-next (brgl/linux.git)
    eebfcb98cdc0 ("gpio: aggregator: fix "_sysfs" prefix check in gpio_aggregator_make_group()")
    2e8636ca3400 ("gpio: aggregator: Fix gpio_aggregator_line_alloc() checking")
    db1baf69e563 ("gpio: aggregator: Return an error if there are no GPIOs in gpio_aggregator_parse()")
    05b43de95add ("gpio: aggregator: Fix error code in gpio_aggregator_activate()")
    d945ff52642d ("gpio: aggregator: Fix leak in gpio_aggregator_parse()")
    290ffcfe3042 ("selftests: gpio: gpio-aggregator: add a test case for _sysfs prefix reservation")

For Oracular, apply 19 patches in total:

  * Cherry-pick 3 commits from mainline, as prerequisite for the main patch series:
    eb5ab6ffb4ca ("gpio: introduce utilities for synchronous fake device creation")
    22dec5aa596e ("gpio: aggregator: simplify aggr_parse() with scoped bitmap")
    12f65d120350 ("gpio: aggregator: protect driver attr handlers against module unload")
  * Cherry-pick 9 commits from linux-next:
    7a56efeabffd ("gpio: aggregator: reorder functions to prepare for configfs introduction")
    7616dd97ae22 ("gpio: aggregator: unify function naming")
    88fe1d1a646b ("gpio: aggregator: add gpio_aggregator_{alloc,free}()")
    86f162e73d2d ("gpio: aggregator: introduce basic configfs interface")
    4ec2315d7fab ("gpio: aggregator: rename 'name' to 'key' in gpio_aggregator_parse()")
    83c8e3df642f ("gpio: aggregator: expose aggregator created via legacy sysfs to configfs")
    0269c768de1b ("gpio: aggregator: cancel deferred probe for devices created via configfs")
    10f94d092bba ("Documentation: gpio: document configfs interface for gpio-aggregator")
    6d7f0c1103ef ("selftests: gpio: add test cases for gpio-aggregator")
  * Cherry-pick 6 commits (follow-up fixes) from gpio/for-next (brgl/linux.git)
    eebfcb98cdc0 ("gpio: aggregator: fix "_sysfs" prefix check in gpio_aggregator_make_group()")
    2e8636ca3400 ("gpio: aggregator: Fix gpio_aggregator_line_alloc() checking")
    db1baf69e563 ("gpio: aggregator: Return an error if there are no GPIOs in gpio_aggregator_parse()")
    05b43de95add ("gpio: aggregator: Fix error code in gpio_aggregator_activate()")
    d945ff52642d ("gpio: aggregator: Fix leak in gpio_aggregator_parse()")
    290ffcfe3042 ("selftests: gpio: gpio-aggregator: add a test case for _sysfs prefix reservation")
  * Add a "UBUNTU: [Config]" commit for the new config option CONFIG_DEV_SYNC_PROBE.

For Noble, apply 20 patches in total:

  * Cherry-pick 4 commits from mainline, as prerequisite for the main patch series:
    eb5ab6ffb4ca ("gpio: introduce utilities for synchronous fake device creation")
    d12a82848eac ("bitmap: Define a cleanup function for bitmaps")
    22dec5aa596e ("gpio: aggregator: simplify aggr_parse() with scoped bitmap")
    12f65d120350 ("gpio: aggregator: protect driver attr handlers against module unload")
  * Cherry-pick 9 commits from linux-next:
    7a56efeabffd ("gpio: aggregator: reorder functions to prepare for configfs introduction")
    7616dd97ae22 ("gpio: aggregator: unify function naming")
    88fe1d1a646b ("gpio: aggregator: add gpio_aggregator_{alloc,free}()")
    86f162e73d2d ("gpio: aggregator: introduce basic configfs interface")
    4ec2315d7fab ("gpio: aggregator: rename 'name' to 'key' in gpio_aggregator_parse()")
    83c8e3df642f ("gpio: aggregator: expose aggregator created via legacy sysfs to configfs")
    0269c768de1b ("gpio: aggregator: cancel deferred probe for devices created via configfs")
    10f94d092bba ("Documentation: gpio: document configfs interface for gpio-aggregator")
    6d7f0c1103ef ("selftests: gpio: add test cases for gpio-aggregator")
  * Cherry-pick 6 commits (follow-up fixes) from gpio/for-next (brgl/linux.git)
    eebfcb98cdc0 ("gpio: aggregator: fix "_sysfs" prefix check in gpio_aggregator_make_group()")
    2e8636ca3400 ("gpio: aggregator: Fix gpio_aggregator_line_alloc() checking")
    db1baf69e563 ("gpio: aggregator: Return an error if there are no GPIOs in gpio_aggregator_parse()")
    05b43de95add ("gpio: aggregator: Fix error code in gpio_aggregator_activate()")
    d945ff52642d ("gpio: aggregator: Fix leak in gpio_aggregator_parse()")
    290ffcfe3042 ("selftests: gpio: gpio-aggregator: add a test case for _sysfs prefix reservation")
  * Add a "UBUNTU: [Config]" commit for the new config option CONFIG_DEV_SYNC_PROBE.

[1] https://lore.kernel.org/all/20250315164123.1855142-1-koichiro.den@canonical.com/
[2] https://lists.ubuntu.com/archives/kernel-team/2025-March/158315.html
[3] https://lore.kernel.org/all/20250407043019.4105613-1-koichiro.den@canonical.com/
[4] https://lore.kernel.org/all/20250221133501.2203897-1-koichiro.den@canonical.com/
[5] https://lore.kernel.org/all/cover.1744452787.git.dan.carpenter@linaro.org/

[ Test Plan ]

Run kselftest.

[ Where problems could occur ]

Any regressions would only impact users who load and use the
gpio-aggregator module, potentially causing issues like memory leaks or
system crashes.

[ Other Info ]

v1->v2 changes:
  - Omitted backports for Jammy. See the comment:
    https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2103496/comments/4
  - Included the follow-up fixes from brgl/linux.git gpio/for-next branch:
    https://lore.kernel.org/all/cover.1744452787.git.dan.carpenter@linaro.org/
    That's why this v2 submission includes Plucky as its target.
    Note that it has not landed into linux-next as of this writing.
  - Fixed messed-up git commit trailers for:
    * [SRU][O][PATCH 01/13]
    * [SRU][O][PATCH 04/13]
    * [SRU][N][PATCH 01/14]
   (* [SRU][J][PATCH 01/12]) # v2 does not include backport for Jammy
   (* [SRU][J][PATCH 04/12]) # v2 does not include backport for Jammy
   (* [SRU][J][PATCH 09/12]) # v2 does not include backport for Jammy