linux-kernel - Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing runtime suspend

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

Date:	Sat, 26 Sep 2015 11:20:50 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
cc:	Oliver Neukum <oneukum@...e.de>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Irina Tirdea <irina.tirdea@...el.com>,
	Len Brown <len.brown@...el.com>,
	Octavian Purdila <octavian.purdila@...el.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Pavel Machek <pavel@....cz>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>
Subject: Re: [RFC PATCH] PM / Runtime: runtime: Add sysfs option for forcing
 runtime suspend

On Sat, 26 Sep 2015, Rafael J. Wysocki wrote:

> > > So something like:
> > > 
> > > 	echo on >/sys/.../power/control  (in case the device was
> > > 			already in runtime suspend with wakeups enabled)
> > > 	echo off >/sys/.../power/wakeup
> > > 	echo auto >/sys/.../power/control

Cases where the driver wants to avoid runtime suspend (while the device
is active) because of bad wakeup support in the hardware can be handled
easily enough.  The runtime-idle or runtime-suspend callback routine
can check whether wakeup == off; if it isn't then the callback should
return -EBUSY.  Thus the driver can prevent runtime suspend without any
need to increment the usage counter.

> > That, or there may be an additional value, say "aggressive", to write to the
> > control file in which case it becomes just
> > 
> > echo aggressive >/sys/.../power/control
> 
> That said I suppose that the "off" value for the "wakeup" file might also be
> useful in some other cases, so it likely is a better approach.

We still need some sort of "inhibit" callback for cases where the
driver doesn't want to go into runtime suspend but does want to turn
off all I/O.  Should this callback be triggered when the user writes
"off" to power/wakeup, or when the user writes "inhibit" to
power/control, or should there be a separate sysfs attribute?

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/