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

Zhang Rui
2014-03-09T05:33:31Z

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@rjwysocki.net]
> > >> Sent: Tuesday, March 04, 2014 7:23 AM
> > >> To: Zhang, Rui
> > >> Cc: linux-acpi@vger.kernel.org; linux-kernel@vger.kernel.org;
> > >> bhelgaas@google.com; matthew.garrett@nebula.com; Wysocki, Rafael J;
> > >> dmitry.torokhov@gmail.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@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?
> > >>
> > > 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?)

thanks,
rui

> Thanks,
> Rafael
>