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From: James Hogan <james@albanarts.com>
To: Pavel Machek <pavel@ucw.cz>
Subject: Re: [PATCH 2/2] pm_trace: Add sysfs attr for rechecking dev hash.
Date: Sun, 10 Oct 2010 20:47:01 +0100
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Cc: linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, Len Brown <len.brown@intel.com>,
        "Rafael J. Wysocki" <rjw@sisk.pl>, Randy Dunlap <rdunlap@xenotime.net>,
        "Greg Kroah-Hartman" <gregkh@suse.de>,
        Alan Stern <stern@rowland.harvard.edu>,
        Jesse Barnes <jbarnes@virtuousgeek.org>,
        markgross <markgross@thegnar.org>
References: <201010092334.27808.james@albanarts.com> <201010092337.47821.james@albanarts.com> <20101010180400.GA19524@elf.ucw.cz>
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Hi Pavel,

On Sunday 10 October 2010 19:04:00 Pavel Machek wrote:
> Hi!
> 
> > If the device which fails to resume is part of a loadable kernel module
> > it won't be checked at startup against the magic number stored in the
> > RTC.
> > 
> > Add a read-only sysfs attribute /sys/power/pm_trace_dev_hash which
> > contains a list of newline separated devices (usually just the one)
> > which currently match the last magic number. This allows the device
> > which is failing to resume to be found after the modules are loaded
> > again.
> > 
> > --- a/Documentation/power/s2ram.txt
> > +++ b/Documentation/power/s2ram.txt
> > 
> > @@ -49,6 +49,13 @@ machine that doesn't boot) is:
> >     device (lspci and /sys/devices/pci* is your friend), and see if you
> >     can fix it, disable it, or trace into its resume function.
> > 
> > +   If no device matches the hash, it may be a device from a loadable
> > kernel +   module that is not loaded until after the hash is checked.
> > You can check +   the hash against the current devices again after more
> > modules are loaded +   using sysfs:
> > +
> > +	cat /sys/power/pm_trace_dev_hash
> > +
> 
> Yep, but exact semantics of that sysfs file should probably be linked
> in the sysfs documentation...
> 								Pavel

To clarify, do you mean I should link to Documentation/ABI/testing/sysfs-power 
from Documentation/power/s2ram.txt, or just make sure the syfs file is 
documented in Documentation/ABI/testing/sysfs-power (which is done in v2 of 
this patch)?

Thanks for taking a look
James