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Date: Mon, 18 Feb 2013 16:48:06 -0500 (EST)
From: Alan Stern <stern@rowland.harvard.edu>
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To: Felipe Balbi <balbi@ti.com>
cc: Greg KH <gregkh@linuxfoundation.org>,
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Subject: Re: SYSFS "errors"
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On Mon, 18 Feb 2013, Felipe Balbi wrote:

> Hi, On Mon, Feb 18, 2013 at 09:49:16AM -0800, Greg KH wrote:
> > > Input/output error - /sys/devices/cpu/power/autosuspend_delay_ms
> > 
> > The issue with this file is, if the power.use_autosuspend flag is not
> > set for the device, then it can't be read or written to.  This flag
> > changes dynamically with the system state
> > (__pm_runtime_use_autosuspend() can change it), so we can't just not
> > show the file if the flag is not set properly, sorry.
> > 
> > So the "error" is correct here, as is the 0644 file value.
> 
> hmm... we could create the file at pm_runtime_enable() time and remove
> it on pm_runtime_disable() time, no ? Addin Rafael to Cc

In theory this could be done, although the times would be when runtime 
autosuspend is turned on or off, not when pm_runtime_enable is called.

Alan Stern