Re: [RFC PATCH 6/8] ACPI: use platform bus as the default bus for _HID enumeration

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

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@intel.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?

Rafael