RE: [PATCH v2 3/7] dt-bindings: thermal: r9a09g047-tsu: Document the TSU unit

John Madieu
2025-03-11T11:27:41Z

Hi Conor,

> -----Original Message-----
> From: Conor Dooley <conor@kernel.org>
> Sent: Monday, March 10, 2025 5:15 PM
> To: John Madieu <john.madieu.xa@bp.renesas.com>
> Subject: Re: [PATCH v2 3/7] dt-bindings: thermal: r9a09g047-tsu: Document
> the TSU unit
>
> On Sun, Mar 09, 2025 at 10:39:27AM +0000, John Madieu wrote:
> > Hi Conor,
> > > > Changes are not possible at runtime. Some customers may want
> > > > software, while other may want the external trigger, and this is
> > > > immutable configuration.
> > >
> > > What makes it immutable? Set by some wiring on the board? I couldn't
> > > find the user in your driver patches to better understand how you
> > > were using it.
> >
> > I haven't prototyped ELC trigger yet. Since the hardware manual
> > describes about ELC trigger, I have documented it in bindings. If you
> > think, it is not needed at this stage, then I can drop it now and
> > revisit later.
>
> Ideally a binding is complete, even if the driver isn't. To me "immutable"
> would mean something like "the trigger type is determined by hardware or
> firmware configuration", but if it is determined by register writes (e.g.
> wired up for elc trigger, but you can opt for software trigger in the
> driver) then it should be a userspace control.

It is complete, and I confirm, this can be changed by register writes.
Apart from defining default to 0, should I implement userspace change
support now ?

Or should I keep it as it is, just setting default to 0 (thus making
the property optional), and add support for userspace change when I add
ELC support.

My other question is, in case I must add userspace change support now, would
sysfs be Ok ? If yes, is there any path recommendations ?

Regards,
John