Re: [patch 2.6.18-rc2-mm 1/2] PM: make /sys/devices/.../power/state optional

[David Brownell <david-b@pacbell.net>]

On Wednesday 16 August 2006 4:57 am, Pavel Machek wrote:
> > Add a new PM_SYSFS_DEPRECATED config option to control whether or
> > not the /sys/devices/.../power/state files are provided.  ...
> 
> Looks good to me, ACK.
> 
> (And sorry for long delay). 

Greg still hasn't merged it; so, no prob.  :)

I updated patch 2/2  so that it doesn't test for the problematic and
incomplete prepare_suspend() method, and to remove prepare_suspend().
(That removal was discussed separately.)



> I guess this should go with it...? OTOH andrew wanted alternative,
> first, before removing the feature... but it is unclear to me if we
> want the feature at all on the production system, so...

How about this one instead?  The issue is not limited to that sysfs
file and its use of PM_EVENT_* codes, that's just the most visible
facet of the problem.

- Dave

Index: o26/Documentation/feature-removal-schedule.txt
===================================================================
--- o26.orig/Documentation/feature-removal-schedule.txt	2006-07-30 22:08:10.000000000 -0700
+++ o26/Documentation/feature-removal-schedule.txt	2006-08-16 11:34:54.000000000 -0700
@@ -6,6 +6,21 @@ be removed from this file.
 
 ---------------------------
 
+What:	/sys/devices/.../power/state
+	dev->power.power_state
+	dpm_runtime_{suspend,resume)()
+When:	July 2007
+Why:	Broken design for runtime control over driver power states, confusing
+	driver-internal runtime power management with:  mechanisms to support
+	system-wide sleep state transitions; event codes that distinguish
+	different phases of swsusp "sleep" transitions; and userspace policy
+	inputs.  This framework was never widely used, and most attempts to
+	use it were broken.  Drivers should instead be exposing domain-specific
+	interfaces either to kernel or to userspace, iff they are even needed.
+Who:	Pavel Machek <pavel@suse.cz>
+
+---------------------------
+
 What:	RAW driver (CONFIG_RAW_DRIVER)
 When:	December 2005
 Why:	declared obsolete since kernel 2.6.3