linux-kernel - Re: [PATCH 5/5] ACPI / scan: Add second pass to acpi_bus

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Date:	Tue, 15 Jan 2013 00:44:49 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Taku Izumi <izumi.taku@...fujitsu.com>
Subject: Re: [PATCH 5/5] ACPI / scan: Add second pass to acpi_bus_trim()

On Monday, January 14, 2013 04:13:43 PM Toshi Kani wrote:
> On Mon, 2013-01-14 at 22:39 +0100, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > 
> > Make acpi_bus_trim() work in analogy with acpi_bus_scan() and carry
> > out two passes such that ACPI drivers will be detached from device
> > nodes being removed in the first pass and the device nodes themselves
> > will be removed in the second pass.
> > 
> > For this purpose split the driver unregistration out of
> > acpi_bus_remove() into a new routine, acpi_bus_device_detach(), that
> > will be executed by acpi_bus_trim() in the additional first pass as
> > a post-order callback.
> > 
> > This is necessary, because some ACPI drivers' .remove() routines
> > unregister struct device objects associated with the ACPI device
> > nodes being removed and that needs to happen while the ACPI
> > device nodes are still around (for example, in case they need to be
> > used for power management or similar things at that time).
> > 
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> I'd suggest to add some comment stating that acpi_bus_device_detach()
> acpi_bus_remove() are post-order callbacks.  I do not think many people
> recognize it by just looking the calls to acpi_walk_namespace().

Yeah, good idea.

> Otherwise, the patchset looks good.  For the patch series:
> Acked-by: Toshi Kani <toshi.kani@...com>

Thanks!

Rafael


> > ---
> >  drivers/acpi/scan.c |   44 ++++++++++++++++++++++++++++----------------
> >  1 file changed, 28 insertions(+), 16 deletions(-)
> > 
> > Index: linux-pm/drivers/acpi/scan.c
> > ===================================================================
> > --- linux-pm.orig/drivers/acpi/scan.c
> > +++ linux-pm/drivers/acpi/scan.c
> > @@ -1425,22 +1425,6 @@ static void acpi_device_set_id(struct ac
> >  	}
> >  }
> >  
> > -static acpi_status acpi_bus_remove(acpi_handle handle, u32 lvl_not_used,
> > -				   void *not_used, void **ret_not_used)
> > -{
> > -	struct acpi_device *dev = NULL;
> > -
> > -	if (acpi_bus_get_device(handle, &dev))
> > -		return AE_OK;
> > -
> > -	dev->removal_type = ACPI_BUS_REMOVAL_EJECT;
> > -	device_release_driver(&dev->dev);
> > -
> > -	acpi_device_unregister(dev);
> > -
> > -	return AE_OK;
> > -}
> > -
> >  void acpi_init_device_object(struct acpi_device *device, acpi_handle handle,
> >  			     int type, unsigned long long sta)
> >  {
> > @@ -1647,8 +1631,36 @@ int acpi_bus_add(acpi_handle handle)
> >  }
> >  EXPORT_SYMBOL(acpi_bus_add);
> >  
> > +static acpi_status acpi_bus_device_detach(acpi_handle handle, u32 lvl_not_used,
> > +					  void *not_used, void **ret_not_used)
> > +{
> > +	struct acpi_device *device = NULL;
> > +
> > +	if (!acpi_bus_get_device(handle, &device)) {
> > +		device->removal_type = ACPI_BUS_REMOVAL_EJECT;
> > +		device_release_driver(&device->dev);
> > +	}
> > +	return AE_OK;
> > +}
> > +
> > +static acpi_status acpi_bus_remove(acpi_handle handle, u32 lvl_not_used,
> > +				   void *not_used, void **ret_not_used)
> > +{
> > +	struct acpi_device *device = NULL;
> > +
> > +	if (!acpi_bus_get_device(handle, &device))
> > +		acpi_device_unregister(device);
> > +
> > +	return AE_OK;
> > +}
> > +
> >  int acpi_bus_trim(struct acpi_device *start)
> >  {
> > +	/* Detach all ACPI drivers from the device nodes being removed. */
> > +	acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
> > +			    acpi_bus_device_detach, NULL, NULL);
> > +	acpi_bus_device_detach(start->handle, 0, NULL, NULL);
> > +	/* Remove the device nodes. */
> >  	acpi_walk_namespace(ACPI_TYPE_ANY, start->handle, ACPI_UINT32_MAX, NULL,
> >  			    acpi_bus_remove, NULL, NULL);
> >  	acpi_bus_remove(start->handle, 0, NULL, NULL);
> > 
> 
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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