Re: [PATCH v6 7/7] Documentation: Add sysfs documentation for PSCRR reboot reason tracking
From: Oleksij Rempel
Date: Fri Mar 14 2025 - 10:10:45 EST
On Fri, Mar 14, 2025 at 03:38:55PM +0200, Matti Vaittinen wrote:
> On 14/03/2025 13:36, Oleksij Rempel wrote:
> > Add documentation for the Power State Change Reason Recorder (PSCRR)
> > sysfs interface, which allows tracking of system shutdown and reboot
> > reasons. The documentation provides details on available sysfs entries
> > under `/sys/kernel/pscrr/`, explaining their functionality, example usage,
> > and how they interact with different backend storage options (e.g., NVMEM).
> >
> > Signed-off-by: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> > ---
> > .../ABI/testing/sysfs-kernel-reboot-pscrr | 46 +++++++++++++++++++
> > 1 file changed, 46 insertions(+)
> > create mode 100644 Documentation/ABI/testing/sysfs-kernel-reboot-pscrr
> >
> > diff --git a/Documentation/ABI/testing/sysfs-kernel-reboot-pscrr b/Documentation/ABI/testing/sysfs-kernel-reboot-pscrr
> > new file mode 100644
> > index 000000000000..7cc643f89675
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-kernel-reboot-pscrr
> > @@ -0,0 +1,46 @@
> > +What: /sys/kernel/pscrr/reason
> > +Date: April 2025
> > +KernelVersion: 6.15
> > +Contact: Oleksij Rempel <o.rempel@xxxxxxxxxxxxxx>
> > +Description:
> > + This file provides access to the last recorded power state
> > + change reason. The storage backend is configurable and, if
> > + supported, the reason may be stored persistently in an
> > + NVMEM cell or another backend.
> > +
> > + Reading this file returns an integer representing the last
> > + recorded shutdown or reboot cause.
> > +
> > + Writing an integer value to this file sets the reason to be
> > + stored and recorded for system analysis.
> > +
> > + Example usage (values are for illustration and may not reflect
> > + actual reasons used in a given system):
> > + Read:
> > + $ cat /sys/kernel/pscrr/reason
> > + 3 # (Example: Power loss event, may differ per system)
> > +
> > + Write:
> > + $ echo 5 > /sys/kernel/pscrr/reason
> > + # Sets the reason to 5 (Example: User-triggered reboot,
> > + # this may not be a real value in your system)
> > +
> > + Values are defined in:
> > + - `include/linux/reboot.h` (enum psc_reason)
>
> Is it possible to provide the reason (also) as string?
>
> I believe we should fix the meaning of the numbers so the ABI is not
> changing for the users. Hence we could as well document the meaning of the
> values(?) If I read the suggestion right, we will in any case have
> predefined set of reasons in the kernel side.
>
> Or, am I missing something?
Yes, it is correct, the values should be fixed for user space. Should
they be documented in this documentation too?
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