Re: Handling multiple inheritance [for CXL]

[Ben Widawsky]

On 21-01-27 21:18:24, Igor Mammedov wrote:
> 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 trying to register my persistent memory as normal system memory. I assume
it's required that I implement the memory interface to do that. If it's not,
that's fine too.

For reference:
https://gitlab.com/bwidawsk/qemu/-/blob/cxl-2.0v3/hw/mem/cxl_type3.c

> >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]: 
> > 20210105165323.783725-1-ben.widawsky@intel.com/">https://lore.kernel.org/qemu-devel/20210105165323.783725-1-ben.widawsky@intel.com/
> > 
>