linux-kernel - Re: [RFC][PATCH] PM: Do not create wakeup sysfs files for devices that cannot wakeup

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Date:	Wed, 19 Jan 2011 17:05:16 -0500 (EST)
From:	Alan Stern <stern@...land.harvard.edu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Linux-pm mailing list <linux-pm@...ts.linux-foundation.org>,
	Len Brown <lenb@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] PM: Do not create wakeup sysfs files for devices
 that cannot wakeup

On Sat, 15 Jan 2011, Rafael J. Wysocki wrote:

> OK, I think that problem is not present any more in the new version of the
> patch, which is appended.
> 
> > Apart from that, it all seems reasonable.  But you should change the
> > description of the wakeup attribute in Documentation/power/devices.txt;  
> > it says that the attribute file is present but empty if the device is
> > not wakeup-capable.
> 
> Right and not only that.  The descriptions in ABI/sysfs-device-power have to be
> updated too.
> 
> Thanks,
> Rafael
> 
> ---
> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: PM: Do not create wakeup sysfs files for devices that cannot wake up
> 
> Currently, wakeup sysfs attributes are created for all devices,
> regardless of whether or not they are wakeup-capable.  This is
> excessive and complicates wakeup device identification from user
> space (i.e. to identify wakeup-capable devices user space has to read
> /sys/devices/.../power/wakeup for all devices and see if they are not
> empty).
> 
> Fix this issue by avoiding to create wakeup sysfs files for devices
> that cannot wake up the system from sleep states (i.e. whose
> power.can_wakeup flags are unset during registration) and modify
> device_set_wakeup_capable() so that it adds (or removes) the relevant
> sysfs attributes if a device's wakeup capability status is changed.

Yes, this all looks okay to me.

Alan Stern

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