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Date:	Sun, 09 Mar 2014 18:50:13 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"matthew.garrett@...ula.com" <matthew.garrett@...ula.com>,
	"dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>
Subject: Re: [RFC PATCH 6/8] ACPI: use platform bus as the default bus for _HID enumeration

On Sunday, March 09, 2014 01:33:27 PM Zhang Rui wrote:
> On Fri, 2014-03-07 at 02:46 +0100, Rafael J. Wysocki wrote:
> > On Tuesday, March 04, 2014 01:35:00 AM Rafael J. Wysocki wrote:
> > > On 3/4/2014 1:27 AM, Zhang, Rui wrote:
> > > >
> > > >> -----Original Message-----
> > > >> From: Rafael J. Wysocki [mailto:rjw@...ysocki.net]
> > > >> Sent: Tuesday, March 04, 2014 7:23 AM
> > > >> To: Zhang, Rui
> > > >> Cc: linux-acpi@...r.kernel.org; linux-kernel@...r.kernel.org;
> > > >> bhelgaas@...gle.com; matthew.garrett@...ula.com; Wysocki, Rafael J;
> > > >> dmitry.torokhov@...il.com
> > > >> Subject: Re: [RFC PATCH 6/8] ACPI: use platform bus as the default bus
> > > >> for _HID enumeration
> > > >> Importance: High
> > > >>
> > > >> On Monday, March 03, 2014 10:11:48 PM Zhang Rui wrote:
> > > >>> On Mon, 2014-03-03 at 00:51 +0100, Rafael J. Wysocki wrote:
> > > >>>> On Wednesday, February 26, 2014 05:11:12 PM Zhang Rui wrote:
> > > >>>>> Because of the growing demand for enumerating ACPI devices to
> > > >>>>> platform bus, this patch changes the code to enumerate ACPI
> > > >>>>> devices with _HID/_CID to platform bus by default, unless the
> > > >> device already has a scan handler attached.
> > > >>>>> Signed-off-by: Zhang Rui <rui.zhang@...el.com>
> > > >>>>> ---
> > > >>>>>   drivers/acpi/acpi_platform.c |   28 ----------------------------
> > > >>>>>   drivers/acpi/scan.c          |   12 ++++++------
> > > >>>>>   2 files changed, 6 insertions(+), 34 deletions(-)
> > > >>>>>
> > > >>>>> diff --git a/drivers/acpi/acpi_platform.c
> > > >>>>> b/drivers/acpi/acpi_platform.c index dbfe49e..33376a9 100644
> > > >>>>> --- a/drivers/acpi/acpi_platform.c
> > > >>>>> +++ b/drivers/acpi/acpi_platform.c
> > > >>>>> @@ -22,24 +22,6 @@
> > > >>>>>
> > > >>>>>   ACPI_MODULE_NAME("platform");
> > > >>>>>
> > > >>>>> -/*
> > > >>>>> - * The following ACPI IDs are known to be suitable for
> > > >>>>> representing as
> > > >>>>> - * platform devices.
> > > >>>>> - */
> > > >>>>> -static const struct acpi_device_id acpi_platform_device_ids[] =
> > > >> {
> > > >>>>> -
> > > >>>>> -	{ "PNP0D40" },
> > > >>>>> -	{ "ACPI0003" },
> > > >>>>> -	{ "VPC2004" },
> > > >>>>> -	{ "BCM4752" },
> > > >>>>> -
> > > >>>>> -	/* Intel Smart Sound Technology */
> > > >>>>> -	{ "INT33C8" },
> > > >>>>> -	{ "80860F28" },
> > > >>>>> -
> > > >>>>> -	{ }
> > > >>>>> -};
> > > >>>>> -
> > > >>>>>   /**
> > > >>>>>    * acpi_create_platform_device - Create platform device for ACPI
> > > >> device node
> > > >>>>>    * @adev: ACPI device node to create a platform device for.
> > > >>>>> @@ -125,13 +107,3 @@ int acpi_create_platform_device(struct
> > > >> acpi_device *adev,
> > > >>>>>   	kfree(resources);
> > > >>>>>   	return 1;
> > > >>>>>   }
> > > >>>>> -
> > > >>>>> -static struct acpi_scan_handler platform_handler = {
> > > >>>>> -	.ids = acpi_platform_device_ids,
> > > >>>>> -	.attach = acpi_create_platform_device,
> > > >>>>> -};
> > > >>>>> -
> > > >>>>> -void __init acpi_platform_init(void) -{
> > > >>>>> -	acpi_scan_add_handler(&platform_handler);
> > > >>>>> -}
> > > >>>>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c index
> > > >>>>> 5967338..61af32e 100644
> > > >>>>> --- a/drivers/acpi/scan.c
> > > >>>>> +++ b/drivers/acpi/scan.c
> > > >>>>> @@ -2022,14 +2022,15 @@ static int
> > > >> acpi_scan_attach_handler(struct acpi_device *device)
> > > >>>>>   		handler = acpi_scan_match_handler(hwid->id, &devid);
> > > >>>>>   		if (handler) {
> > > >>>>>   			ret = handler->attach(device, devid);
> > > >>>>> -			if (ret > 0) {
> > > >>>>> +			if (ret > 0)
> > > >>>>>   				device->handler = handler;
> > > >>>>> -				break;
> > > >>>>> -			} else if (ret < 0) {
> > > >>>>> -				break;
> > > >>>>> -			}
> > > >>>>> +			if (ret)
> > > >>>>> +				goto end;
> > > >>>>>   		}
> > > >>>>>   	}
> > > >>>>> +end:
> > > >>>>> +	if (!list_empty(&device->pnp.ids) && !device->handler)
> > > >>>> I'm a bit concerned that this check will create platform devices
> > > >> for
> > > >>>> too many ACPI device objects.
> > > >>> agreed. there are some devices created unexpected by this patch, e.g.
> > > >>> on my test machine, I can see
> > > >>>
> > > >>> /sys/bus/platform/devices/LNXSYSTM:00 (ACPI system bus/root node)
> > > >>> /sys/bus/platform/devices/PNP0000:00  (PIC)
> > > >>> /sys/bus/platform/devices/PNP0100:00  (system timer?)
> > > >>>
> > > >>>>    Shouldn't we require that _HID or at least _CID is present for
> > > >>>> that?
> > > >>>>
> > > >>> I do not think so.
> > > >>> only devices that invoke acpi_add_ids() may have pnp.ids but no
> > > >>> _HID/_CID, right?
> > > >>> I did a check in the code, those devices include:
> > > >> Well, I did that too.
> > > >>
> > > >>> ACPI root node
> > > >>> ACPI video
> > > >>> ACPI bay
> > > >>> ACPI dock
> > > >>> IBM SMBus
> > > >>> ACPI Power resource
> > > >>> ACPI processor
> > > >>> ACPI thermal
> > > >>> ACPI fixed power/sleep button
> > > >>>
> > > >>> IMO, only the ACPI root node, ACPI power resource, possibly ACPI
> > > >>> processor are the ones that we do not want to see in platform bus.
> > > >> No, we don't want any of them.  So pretty much as I said, only if
> > > >> _HID/_CID is present, please?
> > > >>
> > > > Why? We will convert the drivers for most of those devices from ACPI bus to platform bus sooner or later.
> > > > We need to see them in platform bus...
> > > 
> > > No, we don't.
> > > 
> > > I'm not sure about IBM SMBus to be honest, but as for the rest:
> > > 
> > > Why would we want one for the ACPI root?
> > > 
> > > And for video?  Those things are PCI usually devices anyway and we just 
> > > add "artificial" HIDs for them.
> > > 
> > > ACPI docks and bays are handled by the dock driver which creates 
> > > platform devices for them already if needed and we don't want duplicates 
> > > there.
> > > 
> > > ACPI processor has its own scan handler that binds those objects to 
> > > system devices.
> > > 
> > > Power resources - no need.
> > > 
> > > Do we need platform devices for ACPI thermal zones?
> > > 
> > > Yes, we will need them for fixed buttons, but that's a special case anyway.
> > 
> > So, why don't we add an ACPI device object flag, say hid_device, such that if
> > set, the ACPI core will create a struct platform device for that device object.
> > Then, we can set hid_device for buttons and other stuff we care about.
> > 
> agreed. I will do this in next version.
> But anyway, the exclude list is still needed for the _HID devices that
> we do not want to see in platform, e.g.
> /sys/bus/platform/devices/PNP0000:00  (PIC)
> /sys/bus/platform/devices/PNP0100:00  (system timer?)

I see.

OK

Rafael

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