linux-kernel - Re: [PATCH] ACPI / scan: Always call acpi_bus

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Date:	Thu, 11 Jul 2013 00:45:36 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Toshi Kani <toshi.kani@...com>
Cc:	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>
Subject: Re: [PATCH] ACPI / scan: Always call acpi_bus_scan() for bus check notifications

On Wednesday, July 10, 2013 02:11:05 AM Rafael J. Wysocki wrote:
> On Tuesday, July 09, 2013 01:32:42 PM Toshi Kani wrote:
> > On Mon, 2013-07-08 at 02:10 +0200, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > 
> > > An ACPI_NOTIFY_BUS_CHECK notification means that we should scan the
> > > entire namespace starting from the given handle even if the device
> > > represented by that handle is present (other devices below it may
> > > just have been added).
> > > 
> > > For this reason, modify acpi_scan_bus_device_check() to always run
> > > acpi_bus_scan() if the notification being handled is of type
> > > ACPI_NOTIFY_BUS_CHECK.
> > > 
> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > Cc: 3.10+ <stable@...r.kernel.org>
> > 
> > Acked-by: Toshi Kani <toshi.kani@...com>
> > 
> > But, I think we need the additional patch below.
> 
> Yes, I think you're right.

That said I'd prefer to put the check into acpi_bus_device_attach() like in
the appended patch.

Thanks,
Rafael


---
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Subject: ACPI / scan: Do not try to attach scan handlers to devices having them

In acpi_bus_device_attach(), if there is an ACPI device object
for the given handle and that device object has a scan handler
attached to it already, there's nothing more to do for that handle
and the function should just return success immediately.  Make
that happen.

Reported-by: Toshi Kani <toshi.kani@...com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/acpi/scan.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-pm/drivers/acpi/scan.c
===================================================================
--- linux-pm.orig/drivers/acpi/scan.c
+++ linux-pm/drivers/acpi/scan.c
@@ -1984,6 +1984,9 @@ static acpi_status acpi_bus_device_attac
 	if (acpi_bus_get_device(handle, &device))
 		return AE_CTRL_DEPTH;
 
+	if (device->handler)
+		return AE_OK;
+
 	ret = acpi_scan_attach_handler(device);
 	if (ret)
 		return ret > 0 ? AE_OK : AE_CTRL_DEPTH;

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