linux-kernel - Re: [PATCH 2/2] ACPI / scan: Simplify container driver

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Date:	Thu, 07 Feb 2013 02:32:22 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Yinghai Lu <yinghai@...nel.org>, Jiang Liu <liuj97@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ACPI / scan: Simplify container driver

On Wednesday, February 06, 2013 05:51:42 PM Toshi Kani wrote:
> On Thu, 2013-02-07 at 01:55 +0100, Rafael J. Wysocki wrote:
> > On Wednesday, February 06, 2013 03:32:18 PM Toshi Kani wrote:
> > > On Mon, 2013-02-04 at 00:47 +0100, Rafael J. Wysocki wrote:
> > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > 
> > > > The only useful thing that the ACPI container driver does is to
> > > > install system notify handlers for all container and module device
> > > > objects it finds in the namespace.  The driver structure,
> > > > acpi_container_driver, and the data structures created by its
> > > > .add() callback are in fact not used by the driver, so remove
> > > > them entirely.
> > > > 
> > > > It also makes a little sense to build that driver as a module,
> > > > so make it non-modular and add its initialization to the
> > > > namespace scanning code.
> > > > 
> > > > In addition to that, make the namespace walk callback used for
> > > > installing the notify handlers more straightforward.
> > > 
> > > I think the container driver needs to be registered as an ACPI scan
> > > driver so that sysfs eject will continue to work for container devices,
> > > such as ACPI0004:XX/eject.  Since the container driver does not support
> > > ACPI eject notification (and we have been discussing how system device
> > > hot-plug should work), this sysfs eject is the only way to eject a
> > > container device at this point.  I will send an update patchset that
> > > applies on top of this patch.
> > > 
> > > With the update in my patchset:
> > > Reviewed-by: Toshi Kani <toshi.kani@...com>
> > 
> > Thanks, but I'd like to (1) apply your patch from
> > https://patchwork.kernel.org/patch/2108851/ first and then (2) fold your [2/2]
> > into my [2/2], if you don't mind, and apply that next.
> 
> That's fine by me.
> 
> > Moreover, I'm wondering if the #ifndef FORCE_EJECT thing in acpi_eject_store()
> > actually makes sense after the recent changes to acpi_bus_trim(), because that
> > can't fail now, so the eject will always be carried out.  So perhaps we can
> > simply remove the acpi_device->driver check from there entirely in the first
> > place?
> >
> > If we really want to be able to prevent ejects from happening in some cases,
> > we need to implement something along the lines discussed with Greg.
> 
> acpi_bus_trim() cannot fail, but sysfs eject can fail.  So, I think it
> makes sense to do some validation before calling acpi_bus_trim().  If we
> are to implement the no_eject flag thing, that check needs to be made
> before calling acpi_bus_trim().

Sure, but now the logic seems to be "if FORCE_EJECT is not set, don't eject
devices that have no ACPI drivers", so I'm wondering what the purpose of this
is.  It definitely isn't too obvious. :-)

Thanks,
Rafael


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