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

[Zhang, Rui]

> -----Original Message-----
> From: Rafael J. Wysocki [mailto:rjw@xxxxxxxxxxxxx]
> Sent: Tuesday, March 04, 2014 7:23 AM
> To: Zhang, Rui
> Cc: linux-acpi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> bhelgaas@xxxxxxxxxx; matthew.garrett@xxxxxxxxxx; Wysocki, Rafael J;
> dmitry.torokhov@xxxxxxxxx
> 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@xxxxxxxxx>
> > > > ---
> > > >  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...

Thanks,
rui

> Rafael