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

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Message-ID: <1358205223.14145.108.camel@misato.fc.hp.com>
Date:	Mon, 14 Jan 2013 16:13:43 -0700
From:	Toshi Kani <toshi.kani@...com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
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 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().

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

Thanks,
-Toshi

> ---
>  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);
> 


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