linux-kernel - Re: [RFC PATCH 6/8] ACPI: use platform bus as the default bus for

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Date:	Sun, 09 Mar 2014 19:04:23 +0100
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Zhang Rui <rui.zhang@...el.com>
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	bhelgaas@...gle.com, matthew.garrett@...ula.com,
	rafael.j.wysocki@...el.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 11:50:37 PM Zhang Rui wrote:
> On Wed, 2014-02-26 at 17:11 +0800, 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)
> > +		acpi_create_platform_device(device, NULL);
> 
> I just found a big problem in this proposal, which affects all the
> optional scan handlers.

What do you mean by "optional"?  Such that can be compiled out?

> The problem is that, if we disable a scan handler, platform device nodes
> would be created instead by the code above, because there is no scan
> handler attached for those ACPI nodes.

If "we disable a scan handled" means "we compile it out", I'm not sure
why creating platform devices for the device objects in question will
be incorrect?

Rafael

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