Re: Handling multiple inheritance [for CXL]

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 26 Jan 2021 13:33:52 -0800
Ben Widawsky <ben@bwidawsk.net> wrote:

> I'm working on CXL 2.0 type 3 memory devices [1]. In short, these are PCIe devices
> that have persistent memory on them. As such, it would be nice to inherit from
> both a PCI_DEVICE class as well as an NVDIMM device class.
> 
> Truth be told, using TYPE_MEMORY_DEVICE as the interface does provide most of
> what I need.
could you be more specific on what you need from it?

>I'm wondering what the best way to handle this is. Currently, the
> only thing NVDIMM class provides is write/read_label_data, this is driven by
> _DSM. For CXL, the mechanism to read/write the equivalent area is not done via
> _DSM, but done directly via a mailbox interface. However, the intent is the
> same, and so utilizing similar code seems ideal.
> 
> If there's a desire to unify these code paths, I'd need something like multiple
> inheritance. I'm looking for some feedback here on how to do it.
> 
> Thanks.
> Ben
> 
> [1]: https://lore.kernel.org/qemu-devel/20210105165323.783725-1-ben.widawsky@intel.com/
>