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

Rafael J. Wysocki
2014-03-07T01:31:17Z

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.

Thanks,
Rafael