Meaning / use of acpi_driver.class and acpi_device_class() fields ?

Meaning / use of acpi_driver.class and acpi_device_class() fields ?

[Hans de Goede]

Hi Rafael,

While reviewing a new acpi-driver:
https://patchwork.kernel.org/project/platform-driver-x86/patch/CAFysUkSztjJpSjKA92a=3j3Nj7vfQy5TCsiJtNmfjegxLBvFSA@mail.gmail.com/

I was wondering what the meaning / use of the acpi_driver.class and
acpi_device_class() fields is and if these should be set to anything
specific ?

I did a quick grep and most drivers seem to set this to a string describing
the driver / to the driver-name and they seem to set the 2 fields to the
exact same value. But some drivers also use different values for
acpi_driver.class and acpi_device_class() ?

Regards,

Hans

Re: Meaning / use of acpi_driver.class and acpi_device_class() fields ?

[Rafael J. Wysocki]

Hi Hans,

On Thu, Mar 4, 2021 at 4:24 PM Hans de Goede <hdegoede@redhat.com> wrote:
>
> Hi Rafael,
>
> While reviewing a new acpi-driver:
> https://patchwork.kernel.org/project/platform-driver-x86/patch/CAFysUkSztjJpSjKA92a=3j3Nj7vfQy5TCsiJtNmfjegxLBvFSA@mail.gmail.com/
>
> I was wondering what the meaning / use of the acpi_driver.class and
> acpi_device_class() fields is and if these should be set to anything
> specific ?

The latter is passed to acpi_bus_generate_netlink_event() in multiple
places and that's the only use of it I'm aware of.

The former - I can't recall ATM.

> I did a quick grep and most drivers seem to set this to a string describing
> the driver / to the driver-name and they seem to set the 2 fields to the
> exact same value. But some drivers also use different values for
> acpi_driver.class and acpi_device_class() ?

I don't generally want acpi_driver to be used at all, if that's possible.

Re: Meaning / use of acpi_driver.class and acpi_device_class() fields ?

[Hans de Goede]

Hi,

On 3/4/21 4:53 PM, Rafael J. Wysocki wrote:
> Hi Hans,
> 
> On Thu, Mar 4, 2021 at 4:24 PM Hans de Goede <hdegoede@redhat.com> wrote:
>>
>> Hi Rafael,
>>
>> While reviewing a new acpi-driver:
>> https://patchwork.kernel.org/project/platform-driver-x86/patch/CAFysUkSztjJpSjKA92a=3j3Nj7vfQy5TCsiJtNmfjegxLBvFSA@mail.gmail.com/
>>
>> I was wondering what the meaning / use of the acpi_driver.class and
>> acpi_device_class() fields is and if these should be set to anything
>> specific ?
> 
> The latter is passed to acpi_bus_generate_netlink_event() in multiple
> places and that's the only use of it I'm aware of.
> 
> The former - I can't recall ATM.
> 
>> I did a quick grep and most drivers seem to set this to a string describing
>> the driver / to the driver-name and they seem to set the 2 fields to the
>> exact same value. But some drivers also use different values for
>> acpi_driver.class and acpi_device_class() ?
> 
> I don't generally want acpi_driver to be used at all, if that's possible.

Good point, I would expect the acpi subsys code to also instantiate a platform_dev
for the HID which this driver binds to, so it should be able to just use that.

I'll ask the submitter of the patch to re-write the driver as a platform-driver.

Regards,

Hans