ACPI: platform-profile: call sysfs_notify() from platform_profile_store()

Drivers like thinkpad_acpi and ideapad_laptop call the
platform_profile_notify() helper when the profile is changed by hardware
(the embedded-controller/EC) in response to an EC handled hotkey.

This allows userspace to monitor for such changes by polling for POLLPRI
on the platform_profile sysfs file. But the profile can also be changed
underneath a userspace program monitoring it by anonther userspace program
storing a new value.

Add a sysfs_notify() call to platform_profile_store(), so that userspace
programs monitoring for changes also get notified in this case.

Also update the documentation to document that POLLPRI polling can be
used to watch for changes.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
 Documentation/ABI/testing/sysfs-platform_profile | 7 +++++++
 drivers/acpi/platform_profile.c                  | 3 +++
 2 files changed, 10 insertions(+)

On Mon, Aug 16, 2021 at 1:30 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Drivers like thinkpad_acpi and ideapad_laptop call the
> platform_profile_notify() helper when the profile is changed by hardware
> (the embedded-controller/EC) in response to an EC handled hotkey.
>
> This allows userspace to monitor for such changes by polling for POLLPRI
> on the platform_profile sysfs file. But the profile can also be changed
> underneath a userspace program monitoring it by anonther userspace program
> storing a new value.
>
> Add a sysfs_notify() call to platform_profile_store(), so that userspace
> programs monitoring for changes also get notified in this case.
>
> Also update the documentation to document that POLLPRI polling can be
> used to watch for changes.
>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
> ---
>  Documentation/ABI/testing/sysfs-platform_profile | 7 +++++++
>  drivers/acpi/platform_profile.c                  | 3 +++
>  2 files changed, 10 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-platform_profile b/Documentation/ABI/testing/sysfs-platform_profile
> index dae9c8941905..baf1d125f9f8 100644
> --- a/Documentation/ABI/testing/sysfs-platform_profile
> +++ b/Documentation/ABI/testing/sysfs-platform_profile
> @@ -26,3 +26,10 @@ Contact:     Hans de Goede <hdegoede@redhat.com>
>  Description:   Reading this file gives the current selected profile for this
>                 device. Writing this file with one of the strings from
>                 platform_profile_choices changes the profile to the new value.
> +
> +               This file can be monitored for changes by polling for POLLPRI,
> +               POLLPRI will be signalled on any changes, independent of those
> +               changes coming from a userspace write; or coming from another
> +               source such as e.g. a hotkey triggered profile change handled
> +               either directly by the embedded-controller or fully handled
> +               inside the kernel.
> diff --git a/drivers/acpi/platform_profile.c b/drivers/acpi/platform_profile.c
> index dd2fbf38e414..d418462ab791 100644
> --- a/drivers/acpi/platform_profile.c
> +++ b/drivers/acpi/platform_profile.c
> @@ -106,6 +106,9 @@ static ssize_t platform_profile_store(struct device *dev,
>         }
>
>         err = cur_profile->profile_set(cur_profile, i);
> +       if (!err)
> +               sysfs_notify(acpi_kobj, NULL, "platform_profile");
> +
>         mutex_unlock(&profile_lock);
>         if (err)
>                 return err;
> --

Applied as 5.15 material, thanks!