Re: [Ksummit-discuss] [TECH TOPIC] Driver model/resources, ACPI, DT, etc (sigh)

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Thursday, May 08, 2014 01:36:03 PM Linus Walleij wrote:
> On Tue, May 6, 2014 at 1:41 PM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> > On Monday, May 05, 2014 07:41:04 PM Linus Walleij wrote:
> (...)
> >> The thing is: with things like BayTrail I already *know* the pin control
> >> registers are there, they are just not implemented any handling of.
> >> I know very well how much the HW implementers think that a kernel
> >> "should never touch" these registers, and I know it will invariably happen
> >> sooner or later but like to be proven wrong.
> (...)
> 
> > That doesn't mean that we can switch x86 to over DTs (that currently is not an
> > option for various reasons, not necessarily techical), but we may be able to put
> > DT-style information that the current code expects to be there into the ACPI
> > tables.
> 
> In this case I don't care so much about DT or ACPI or whatever, what
> I would like to see is that the hardware is adequately described to
> the kernel, and the subsystem has a pretty good idea about how to
> describe such hardware, and the idea is *not* per-pin properties
> tied to some "GPIO" like I have seen, but concepts like groups and
> functions and per-pin configuration tied in to a certain use case.
> 
> I know DT is doing it right but that is just because the person who
> did the heavy lifting, Stephen Warren, was also a co-author of the
> pin control subsystem.

I haven't been following the development of the pin control subsystem and
I'm not familiar with those things, so I'm not sure how I can aswer this.

>From the firmware interface perspective, though, ACPI has no means of
exposing pin control to the OS today and they way for it I can see,
personally, would be to re-use what is done in the DT space.

That's why I was asking the questions about pin control in the other LKML
thread.  [Thanks for you reply BTW, sorry for not responding there, but
I haven't had a chance to read it carefully yet.]

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.