On 30.09.2024 22:20, Alex Williamson wrote:
> On Tue, 17 Sep 2024 09:57:23 +0200
> Heiner Kallweit <hkallweit1@xxxxxxxxx> wrote:
>
>> After 7e722083fcc3 ("i2c: Remove I2C_COMPAT config symbol and related code")
>> vfio/mdev is that last user of class_compat. This compatibility functionality
>> is meant to be used temporarily, and it has been in vfio/mdev since 2016.
>> Can it be removed? Or is there any userspace tool which hasn't been updated
>> to use the bus interface instead?
>> If class_compat can be removed in vfio/mdev, then we may be able to remove
>> this functionality completely.
>>
>
> Hi Heiner,
>
> I'm afraid we have active userspace tools dependent on
> /sys/class/mdev_bus currently, libvirt for one. We link mdev parent
> devices here and I believe it's the only way for userspace to find
> those parent devices registered for creating mdev devices. If there's a
> desire to remove class_compat, we might need to add some mdev
> infrastructure to register the class ourselves to maintain the parent
> links. Thanks,
>
I see, thanks for the explanation. So class_compat isn't used here with
the original intention in mind, but just as a convenient method to create
a container for the mdev parent links (which wouldn't necessarily have
to reside under /sys/class).
> Alex
>
Heiner
