linux-kernel - Re: [Suspend-devel] 2.6.25-rc2 System no longer powers off aftersuspend-to-disk. Screen becomes green.

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Message-ID: <20080222130615.GA29123@elte.hu>
Date:	Fri, 22 Feb 2008 14:06:15 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Matthew Garrett <mjg59@...f.ucam.org>
Cc:	Jeff Chua <jeff.chua.linux@...il.com>,
	Jesse Barnes <jesse.barnes@...el.com>,
	Romano Giannetti <romano@....icai.upcomillas.es>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	suspend-devel List <suspend-devel@...ts.sourceforge.net>,
	Dave Airlie <airlied@...ux.ie>, Greg KH <gregkh@...e.de>,
	lkml <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>, linux-acpi@...r.kernel.org
Subject: Re: [Suspend-devel] 2.6.25-rc2 System no longer powers off
	aftersuspend-to-disk. Screen becomes green.

* Matthew Garrett <mjg59@...f.ucam.org> wrote:

> The s2ram command has a built-in whitelist used to set up video 
> rePOSTing. If you want to test, reboot and do
> 
> echo mem >/sys/power/state
> 
> without i915 being loaded. If you get a console back on resume then 
> the platform is reinitialising video for you, but otherwise it's your 
> userspace.

btw., why isnt there an in-kernel whitelist, with perhaps a dynamic, 
convenient /debug/s2r/whitelist append-API for distros (and testers) to 
add more entries to the whitelist/blacklist? (for cases where the kernel 
whitelist has not caught up yet) Which would eventually converge to 
Utopia: s2ram that just works out of box.

This would be a lot more flexible (people could even temporarily extend 
the whitelist via rc.local if need to be, etc.), a lot more robust and a 
lot more user friendly than the "dont use /sys/power/state, rely on some 
user-space tool to work around bugs" approach.

Really, i couldnt make the s2ram API/quirks situation much worse even if 
i deliberately tried to design the whole code to be as hard to use and 
as confusing as possible :-/ These types of half-kernel half-userspace 
solutions usually result in constant finger-pointing and constant lag, 
and they result in about the crappiest user experience that is possible 
to achieve physically.

( Sorry about the strong words, while there's lots of good and positive
  development lately i havent seen much change in this particular area
  of s2ram in the past 1-2 years, and the whole chain is only as strong
  as the weakest link - so someone finally has to deliver this message
  to the cozy fire of s2r hackers while our testers and users are 
  standing out in the cold rain ... )

	Ingo
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