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

[Oleksij Rempel <o.rempel@pengutronix.de>]

On Mon, Mar 17, 2025 at 10:46:01AM +0200, Matti Vaittinen wrote:
> 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@pengutronix.de>
> > > > ---
> > > >    .../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@pengutronix.de>
> > > > +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.

Ok, i'll send updated patch set. I'll be happy to have your Reviewed-by
:)

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