linux-kernel - Re: [PATCH 1/2] PM / Runtime: Add sysfs switch for disabling device run-time PM (rev. 2)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Fri, 5 Feb 2010 10:19:18 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Pavel Machek <pavel@....cz>
cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	pm list <linux-pm@...ts.linux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Matthew Garrett <mjg59@...f.ucam.org>, Greg KH <greg@...ah.com>
Subject: Re: [PATCH 1/2] PM / Runtime: Add sysfs switch for disabling device
 run-time PM (rev. 2)

On Fri, 5 Feb 2010, Pavel Machek wrote:

> 
> > > > + *	The default for all devices is "auto", which means that devices may be
> > > > + *	subject to automatic power management, depending on their drivers.
> > > 
> > > Is it wise to specify 'auto' default value for devices without runtime
> > > pm?
> > 
> > Yes, it is.  It means the user space doesn't care whether or not the device is
> > power managed at run-time.
> 
> Well, defaulting to 'on' for drivers when runtime pm is experimental
> seems logical. and there will be such drivers...

It's really not very important what the default setting is.  Runtime PM
is always initially disabled, regardless of the "auto"/"on" setting,
until the driver explicitly enables it.  At that time the driver also
has the option of changing the setting from "auto" to "on".

So if a driver writer wants to support runtime PM but thinks that his
implementation (or the device!) may be buggy, he can easily arrange
things so the user has to change the sysfs setting to make anything
happen.

Alan Stern

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/