Re: [PATCH?] Move ACPI device nodes under /sys/firmware/acpi (was: Re: [RFC PATCH v2 01/12] Add sys_hotplug.h for system device hotplug framework)

From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: linux-s390@vger.kernel.org, Toshi Kani <toshi.kani@hp.com>,
	jiang.liu@huawei.com, wency@cn.fujitsu.com,
	linux-acpi@vger.kernel.org, yinghai@kernel.org,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	isimatu.yasuaki@jp.fujitsu.com, srivatsa.bhat@linux.vnet.ibm.com,
	guohanjun@huawei.com, bhelgaas@google.com,
	akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org,
	lenb@kernel.org
Subject: Re: [PATCH?] Move ACPI device nodes under /sys/firmware/acpi (was: Re: [RFC PATCH v2 01/12] Add sys_hotplug.h for system device hotplug framework)
Date: Mon, 04 Feb 2013 13:34:02 +0100	[thread overview]
Message-ID: <2107169.R5mOc9qh97@vostro.rjw.lan> (raw)
In-Reply-To: <20130204012447.GB6433@kroah.com>

On Sunday, February 03, 2013 07:24:47 PM Greg KH wrote:
> On Sat, Feb 02, 2013 at 11:18:20PM +0100, Rafael J. Wysocki wrote:
> > On Saturday, February 02, 2013 09:15:37 PM Rafael J. Wysocki wrote:
> > > On Saturday, February 02, 2013 03:58:01 PM Greg KH wrote:
> > [...]
> > > 
> > > > I know it's more complicated with these types of devices, and I think we
> > > > are getting closer to the correct solution, I just don't want to ever
> > > > see duplicate devices in the driver model for the same physical device.
> > > 
> > > Do you mean two things based on struct device for the same hardware component?
> > > That's been happening already pretty much forever for every PCI device known
> > > to the ACPI layer, for PNP and many others.  However, those ACPI things are (or
> > > rather should be, but we're going to clean that up) only for convenience (to be
> > > able to see the namespace structure and related things in sysfs).  So the stuff
> > > under /sys/devices/LNXSYSTM\:00/ is not "real".  In my view it shouldn't even
> > > be under /sys/devices/ (/sys/firmware/acpi/ seems to be a better place for it),
> > > but that may be difficult to change without breaking user space (maybe we can
> > > just symlink it from /sys/devices/ or something).  And the ACPI bus type
> > > shouldn't even exist in my opinion.
> > 
> > Well, well.
> > 
> > In fact, the appended patch moves the whole ACPI device nodes tree under
> > /sys/firmware/acpi/ and I'm not seeing any negative consequences of that on my
> > test box (events work and so on).  User space is quite new on it, though, and
> > the patch is hackish.
> 
> Try booting a RHEL 5 image on this type of kernel, or some old Fedora
> releases, they were sensitive to changes in sysfs.

Well, I've found a machine where it causes problems to happen.

I'll try to add a symlink from /sys/devices to that and see what happens then.

Thanks,
Rafael

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.