linux-kernel - Re: [PATCH 6/6] ACPI: Change the ordering of acpi_bus_check

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Date:	Thu, 13 Dec 2012 13:20:42 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	linux-pci@...r.kernel.org, Yinghai Lu <yinghai@...nel.org>,
	Toshi Kani <toshi.kani@...com>,
	Myron Stowe <myron.stowe@...hat.com>
Subject: Re: [PATCH 6/6] ACPI: Change the ordering of acpi_bus_check_add()

On Wednesday, December 12, 2012 06:00:28 PM Bjorn Helgaas wrote:
> On Sun, Dec 9, 2012 at 4:04 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> >
> > If acpi_bus_check_add() is called for a handle already having an
> > existing struct acpi_device object attached, it is not necessary to
> > check the type and status of the device correspondig to it, so
> > change the ordering of acpi_bus_check_add() to avoid that.
> >
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > ---
> >  drivers/acpi/scan.c |   18 +++++++++---------
> >  1 file changed, 9 insertions(+), 9 deletions(-)
> >
> > Index: linux/drivers/acpi/scan.c
> > ===================================================================
> > --- linux.orig/drivers/acpi/scan.c
> > +++ linux/drivers/acpi/scan.c
> > @@ -1582,6 +1582,10 @@ static acpi_status acpi_bus_check_add(ac
> >         acpi_status status;
> >         int result;
> >
> > +       acpi_bus_get_device(handle, &device);
> > +       if (device)
> > +               goto out;
> > +
> >         result = acpi_bus_type_and_status(handle, &type, &sta);
> >         if (result)
> >                 return AE_OK;
> > @@ -1602,17 +1606,13 @@ static acpi_status acpi_bus_check_add(ac
> >          * We may already have an acpi_device from a previous enumeration.  If
> >          * so, we needn't add it again, but we may still have to start it.
> 
> It looks like this comment might need updating, since we no longer
> even get here if we already have an acpi_device.  Presumably you take
> care of the "start" it mentions elsewhere now.

I think you're right, will update.

Thanks,
Rafael


> >          */
> > -       acpi_bus_get_device(handle, &device);
> > -       if (!device) {
> > -               acpi_add_single_object(&device, handle, type, sta,
> > -                                      ACPI_BUS_ADD_BASIC);
> > -               if (!device)
> > -                       return AE_CTRL_DEPTH;
> > +       acpi_add_single_object(&device, handle, type, sta, ACPI_BUS_ADD_BASIC);
> > +       if (!device)
> > +               return AE_CTRL_DEPTH;
> >
> > -               device->add_type = context ?
> > -                                       ACPI_BUS_ADD_START : ACPI_BUS_ADD_MATCH;
> > -       }
> > +       device->add_type = context ? ACPI_BUS_ADD_START : ACPI_BUS_ADD_MATCH;
> >
> > + out:
> >         if (!*return_value)
> >                 *return_value = device;
> 
> I think all (both) callers of acpi_bus_check_add() supply a
> return_value pointer, so you could just remove the test.
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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