Re: hwmon driver with misc interface

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Wed, 2018-07-11 at 09:26 +1000, Benjamin Herrenschmidt wrote:
> On Tue, 2018-07-10 at 13:44 -0700, Guenter Roeck wrote:
> > > > Yes, I think that would be more appropriate.
> > > 
> > > This still won't work, since then we wouldn't have those attributes
> > > available in the P8 version of the driver (which has no fsi-occ driver). In
> > > addition, how would the poll response data get from the hwmon driver to the
> > > fsi-occ driver? Yet another interface? Seems awkward.
> > > 
> > > How about debugfs? We don't really mind where the attributes are, just that
> > > the data is exposed somewhere...
> > > 
> > 
> > You are essentially confirming that using sysfs attributes would not be
> > appropriate. I have no problems with using debugfs; you have a free ride
> > there.
> 
> I disagree.
> 
> If the attributes are used for the normal operation of the system then
> they should be in sysfs.
> 
> A system should be able to function normally without debugfs mounted.
> 
> Those attributes are about monitoring proper operations of the OCC
> right ? Or are there other things here ? I don't see any reason why
> those couldn't hang off the device sysfs node...

Eddie: If Guenter really strongly objects to that handful of attributes
being in the hwmon device itself, then we have two alternatives we can
consider:

  - Not upstream P8 :-)

  - Use a similar 2-level driver for P8/i2c, which additionally
provides the ability to create a p8 variant of /dev/occ if needed.

I don't like the way the P8 backend works today anyway. It basically
uses i2c to do SCOMs which will race/clash with anything else in the
system trying to do the same.

We should ideally have a pure "SCOM" driver providing a P8 /dev/scom
and lay on top of that a platform device for OCC like we do with
sbefifo.

That said, I'm also not too fussed about leaving P8 behind as legacy
and not upstreaming it.

Cheers,
Ben.
> 
> Cheers,
> Ben.
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