Re: [PATCH 2/2] PCI/NPEM: Add Native PCIe Enclosure Management support

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Mar 12, 2024 at 10:08:16AM +0100, Mariusz Tkaczyk wrote:
> On Mon, 11 Mar 2024 17:30:06 -0500
> Stuart Hayes <stuart.w.hayes@gmail.com> wrote:
> 
> > > > No, Linux doesn't support _DSM. It was proposed in previous
> > > > iterations by Stuart but I dropped it. We decided that it need to be
> > > > strongly rebuild because "pci/pcie" is not right place for ACPI code
> > > > so we cannot register _DSM driver instead of NPEM as it was proposed
> > > > and I don't have _DSM capable hardware to test it.  
> > 
> > I'm not sure I understand why pci/pcie isn't the right place for ACPI code--
> > there are other _DSMs used in PCI code already, and this _DSM is defined
> > in a PCI ECN.
> 
> I looked into internal review history and I found out that I dropped it after
> discussion with Dan Williams:
> 
> > After review and discussion with Dan _DSM extension is dropped.
> 
> Unfortunately, I don't remember what exactly he suggested, I just remembered
> conclusion that it needs to be reworked and I decided to drop it.
> Maybe, I didn't understand him correctly.
> 
> Dan, could you take a look? Do you remember something?

Straw man proposal:

  - Update this patch so we use NPEM if the device advertises it.

  - If/when Linux support for the _DSM is added, we use the _DSM when
    present.  If a device advertises NPEM but no _DSM applies to it,
    we use native NPEM for it.

Bjorn