Re: [PATCH v6 7/7] Documentation: Add sysfs documentation for PSCRR reboot reason tracking

[Matti Vaittinen]

On 14/03/2025 16:10, Oleksij Rempel wrote:
> 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?

I believe it could be helpful for both the user-space users and 
potential pscrr provider driver writers. It could also set things to stone.

But, I don't have much experience on the documentation like this so 
please treat this as a suggestion - but do as you see fits best.

Yours,
	-- Matti