Re: [RFC PATCH 1/2] ACPI / scan: Add support for ACPI _CLS device matching

[Suravee Suthikulanit]

On 12/19/2014 12:47 PM, Suravee Suthikulanit wrote:
> On 12/19/2014 8:56 AM, Hanjun Guo wrote:
> > Hi Suravee,
> >
> > On 2014å12æ18æ 07:16, Suravee Suthikulpanit wrote:
> > > From: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
> > >
> > > Device drivers typically use ACPI _HIDs/_CIDs listed in struct
> > > device_driver
> > > acpi_match_table to match devices. However, for generic drivers, we do
> > > not want to list _HID for all supported devices, and some device classes
> > > do not have _CID (e.g. SATA, USB). Instead, we can leverage ACPI _CLS,
> > > which specifies PCI-defined class code (i.e. base-class, subclass and
> > > programming interface).
> > >
> > > This patch adds support for matching ACPI devices using the _CLS method.
> > >
> > > Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
> > > ---
> > >   drivers/acpi/scan.c             | 73
> > > +++++++++++++++++++++++++++++++++++++++++
> > >   include/acpi/acnames.h          |  1 +
> > >   include/linux/acpi.h            | 12 ++++++-
> > >   include/linux/device.h          |  1 +
> > >   include/linux/mod_devicetable.h |  6 ++++
> > >   5 files changed, 92 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> > > index d670158..6406648 100644
> > > --- a/drivers/acpi/scan.c
> > > +++ b/drivers/acpi/scan.c
> > > @@ -864,6 +864,79 @@ int acpi_match_device_ids(struct acpi_device
> > > *device,
> > >   }
> > >   EXPORT_SYMBOL(acpi_match_device_ids);
> > >
> > > +/**
> > > + * acpi_match_device_cls - Match a struct device against a ACPI _CLS
> > > method
> > > + * @dev_cls: A pointer to struct acpi_device_cls object to match
> > > against.
> > > + * @dev: The ACPI device structure to match.
> > > + *
> > > + * Check if @dev has a valid ACPI and _CLS handle. If there is a
> > > + * struct acpi_device_cls object for that handle, use that object to
> > > match
> > > + * against the given struct acpi_device_cls object.
> > > + *
> > > + * Return 0 on success or error code on failure.
> > > + */
> > > +int acpi_match_device_cls(const struct acpi_device_cls *dev_cls,
> > > +              const struct device *dev)
> > > +{
> > > +    int ret = -EINVAL;
> > > +    acpi_status status;
> > > +    struct acpi_device *adev;
> > > +    union acpi_object *pkg;
> > > +    struct acpi_device_cls cls;
> > > +    struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> > > +    struct acpi_buffer format = { sizeof("NNN"), "NNN" };
> > > +    struct acpi_buffer state = { 0, NULL };
> > > +    acpi_handle handle = ACPI_HANDLE(dev);
> >
> > ...
> >
> > > +    acpi_handle cls_handle;
> > > +
> > > +    if (!handle || acpi_bus_get_device(handle, &adev))
> >
> > if handle is not NULL, adev will not NULL too :)
> > because you get the handle from adev, ACPI_HANDLE() is defined as:
> > acpi_device_handle(ACPI_COMPANION(dev)), and adev = ACPI_COMPANION(dev);
> >
> > you may use adev = ACPI_COMPANION(dev) to simplify the code.

Thanks for the pointer.

> > > +        return ret;
> > > +
> > > +    if (!adev->status.present || !dev_cls)
> > > +        return ret;
> > > +
> > > +    status = acpi_get_handle(adev->handle, METHOD_NAME__CLS,
> > > &cls_handle);
> >
> > do we need this function called here? _CLS is the method under ACPI
> > device object in DSDT/SSDT, and you will get adev->handle == cls_handle
> > if I'm not wrong :)

You are right. It is not needed, and we can just evaluate right from the 
handle.

> > > +    if (ACPI_FAILURE(status))
> > > +        return ret;
> > > +
> > > +    status = acpi_evaluate_object(cls_handle, "_CLS", NULL, &buffer);
> > > +    if (ACPI_FAILURE(status)) {
> > > +        ACPI_EXCEPTION((AE_INFO, status, "Failed to Evaluat _CLS"));
> > > +        return ret;
> > > +    }
> >
> > I think you can evaluate _CLS directly with handle here.
> >
> > Thanks
> > Hanjun

Yep. I will send out the new patch in a bit.

Thanks,

Suravee




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