linux-kernel - Re: [patch 2.6.21-rc5-git] make /proc/acpi/wakeup more useful

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Message-Id: <200704050358.43689.david-b@pacbell.net>
Date:	Thu, 5 Apr 2007 03:58:43 -0700
From:	David Brownell <david-b@...bell.net>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	Linux Kernel list <linux-kernel@...r.kernel.org>,
	"linux-acpi@...r" <linux-acpi@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [patch 2.6.21-rc5-git] make /proc/acpi/wakeup more useful

On Thursday 05 April 2007 12:59 am, Zhang Rui wrote:
> On Wed, 2007-04-04 at 08:41 +0800, David Brownell wrote:
> > In that example, two devices don't actually exist (USB3, S139), one can't
> > issue wakeup events (PCI0), and two seem harmlessly (?) confused (MDM and
> > AUD are the same PCI device, but it's the _modem_ that does wake-on-ring). 
> > 
> Well, ACPI can't find the sysfs node for all the wakeup-enabled devices.

The only example of that type in the example I provided is SLPB, where the
sysfs node is ACPI-internal; I'm not sure how one can detect such cases.

> In fact, only pci and pnp devices can be found now.

Well, PNP courtesy of a previous patch from me, but remember that I was
using that as an example of a ** BOGUS ACPI TABLE ** as summarized above.
In my observation, such bogus tables are common.  (This particular one
was, I believe, copied from a system using a higher end version of the
same southbridge ... but which may well have had its own errors.)

> ACPI needs the ability to distinguish all the physical devices, i.e. map
> ACPI device to physical device nodes in sysfs, which I mentioned before.

For wakeup devices, the main issue I've seen is with button devices.
In my limited set of test sytems, everything else is either PCI, PNP,
or a bug (listing a non-existent device).

If this patch starts to get deployed, I expect other people will find
a few other curiousities ... and likely some things to be fixed.

The /sys/devices/acpi_system:00/ tree is kind of new.  I suspect one
way it could be more informative is to set up cross-links in sysfs
between the ACPI devices and the "real" device nodes ... e.g. on the
system I'm using right now .../device:00/PNP0A03:00/device:15/PNP0B00:00
could have a link pointing to /sys/devices/pnp0/00:06 ... and that PNP
node in turn could have an "acpi" link pointing back to the ACPI thing.

Such cross-links would let people see those relationships, and observe
which links are missing or otherwise strange.  Fixing the bugs would
seem unlikely until those things become visible.

- Dave
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