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

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Message-ID: <20140621185051.GA25094@amd.pavel.ucw.cz>
Date:	Sat, 21 Jun 2014 20:50:51 +0200
From:	Pavel Machek <pavel@....cz>
To:	Ilia Mirkin <imirkin@...m.mit.edu>
Cc:	kernel list <linux-kernel@...r.kernel.org>,
	Ben Skeggs <bskeggs@...hat.com>, Greg KH <greg@...ah.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 Sat 2014-06-21 14:22:59, 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.
...
> 
> FTR, this file has been in place since 3.13, and there was a different
> file before it (performance_levels), with a comparable format since
> much earlier (definitely 3.8, probably earlier). I think it's meant
> a

According to the article, it is only starting to work now. I know
articles can be wrong, but I don't have that hardware... Sorry if it
is the case.

> lot more for people looking at it and echo'ing stuff to it to modify
> the levels (where supported), than for programs parsing it. Perhaps
> sysfs is the wrong place for this -- what is the right place? debugfs?

debugfs would work, yes.
									Pavel
-- 
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