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

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Date:	Wed, 06 Feb 2013 17:51:42 -0700
From:	Toshi Kani <toshi.kani@...com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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 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().

Thanks,
-Toshi




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