linux-kernel - Re: unparseable, undocumented /sys/class/drm/.../pstate

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Date:	Mon, 23 Jun 2014 15:02:59 +0200
From:	Pavel Machek <pavel@....cz>
To:	Ilia Mirkin <imirkin@...m.mit.edu>
Cc:	Greg KH <greg@...ah.com>,
	kernel list <linux-kernel@...r.kernel.org>,
	Ben Skeggs <bskeggs@...hat.com>,
	Alexandre Courbot <acourbot@...dia.com>,
	David Airlie <airlied@...ux.ie>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: unparseable, undocumented /sys/class/drm/.../pstate

On Sun 2014-06-22 22:12:14, Ilia Mirkin wrote:
> On Sat, Jun 21, 2014 at 3:45 PM, Greg KH <greg@...ah.com> wrote:
> > On Sat, Jun 21, 2014 at 02:22:59PM -0400, Ilia Mirkin wrote:
> >> On Sat, Jun 21, 2014 at 2:02 PM, Pavel Machek <pavel@....cz> wrote:
> >> > Hi!
> >> >
> >> > AFAICT, pstate file will contain something like
> >> >
> >> > 07: core 100 MHz memory 123 MHz *
> >> > 08: core 100-200 MHz memory 123 MHz
> >> >
> >> > ...which does not look exactly like one-value-per-file, and I'm pretty
> >> > sure userspace will get it wrong if it tries to parse it. Plus, I
> >> > don't see required documentation in Documentation/ABI.
> >> >
> >> > Should we disable it for now, so that userspace does not start
> >> > depending on it and we'll not have to maintain it forever?
> >> >
> >> > I guess better interface would be something like
> >> >
> >> > pstate/07/core_clock_min
> >> >           core_clock_max
> >> >           memory_clock_min
> >> >           memory_clock_max
> >> >
> >> > and then pstate/active containing just the number of active state?

> Could we just say that the format of this file is one-per-line of
> 
> level: information-for-the-user

But it is not. Management tools will want to parse it, sooner or
later.  What is wrong with solution described above?

> And you can echo a level into it to switch to that level? That seems
> like a reasonable ABI to have... would be happy to throw it into a
> file somewhere... not sure where though.

Documentation/ABI/testing/

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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