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

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Message-ID: <20140621180201.GA4621@amd.pavel.ucw.cz>
Date:	Sat, 21 Jun 2014 20:02:01 +0200
From:	Pavel Machek <pavel@....cz>
To:	kernel list <linux-kernel@...r.kernel.org>, bskeggs@...hat.com,
	Greg KH <greg@...ah.com>, acourbot@...dia.com,
	airlied@...ux.ie, dri-devel@...ts.freedesktop.org
Subject: unparseable, undocumented /sys/class/drm/.../pstate

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?

Thanks,
								Pavel

PS: I have no nvidia, got the news at

http://www.phoronix.com/scan.php?page=article&item=nouveau_try_linux316&num=2
-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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