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

Fri Apr 11 12:14:04 UTC 2025

On 11.04.2025 09:26, Koichiro Den wrote:
> 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/Jammy 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, (already) applied 12 patches in total:
>
>    * 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.
>
> For Oracular, apply 13 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")
>    * Add a "UBUNTU: [Config]" commit for the new config option CONFIG_DEV_SYNC_PROBE.
>
> For Noble, apply 14 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")
>    * Add a "UBUNTU: [Config]" commit for the new config option CONFIG_DEV_SYNC_PROBE.
>
> For Jammy, apply 12 patches in total:
>
>    * Cherry-pick/Backport 3 commits from mainline, as prerequisite for the main patch series:
>      eb5ab6ffb4ca ("gpio: introduce utilities for synchronous fake device creation") [5]
>      95b39792c664 ("gpio: aggregator: Stop using ARCH_NR_GPIOS")
>      39ebbd52b73d ("gpio: aggregator: Add missing header(s)")
>    * Cherry-pick/Backport 8 commits from linux-next:
>      7a56efeabffd ("gpio: aggregator: reorder functions to prepare for configfs introduction") [5]
>      7616dd97ae22 ("gpio: aggregator: unify function naming")
>      88fe1d1a646b ("gpio: aggregator: add gpio_aggregator_{alloc,free}()") [5]
>      86f162e73d2d ("gpio: aggregator: introduce basic configfs interface") [5]
>      4ec2315d7fab ("gpio: aggregator: rename 'name' to 'key' in gpio_aggregator_parse()") [5]
>      83c8e3df642f ("gpio: aggregator: expose aggregator created via legacy sysfs to configfs") [5]
>      0269c768de1b ("gpio: aggregator: cancel deferred probe for devices created via configfs")
>      10f94d092bba ("Documentation: gpio: document configfs interface for gpio-aggregator")
>    * 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] Some adjustments were needed (i.e. backporting). The details are explained
>      in the commit message trailers.
>
> [ Test Plan ]
>
> For Plucky/Oracular/Noble, run kselftest.
>
> For Jammy, either test (play) on real hardware, or run kselftest from:
> https://git.launchpad.net/~koichiroden/+git/jammy/log/?h=kselftest-for-gpio-aggr-configfs-backport-to-jammy
> N.B. kselftest for gpio-aggregator is unavailable due to the missing gpio-sim
> on Jammy, and this SRU patch submission does not backport it, as doing so would
> be excessive.
>
> [ 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.
>
Acked-by: Kuba Pawlak <kuba.pawlak at canonical.com>
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