Re: [PATCH v8 4/5] cxl/core, EINJ: Add CXL debugfs files and EINJ functions

[Dan Williams <dan.j.williams@intel.com>]

Ben Cheatham wrote:
[..]
> >> +
> >> +	dir = cxl_debugfs_create_dir(dev_name(dport->dport_dev));
> >> +
> >> +	debugfs_create_file("einj_inject", 0200, dir, dport,
> >> +			    &cxl_einj_inject_fops);
> > 
> > I will note that I am little bit uneasy about this ACPI'ism escaping
> > into the common core, but he mitigation for me is that if some other
> > platform firmware invented a platform-firmware method for error inject
> > it would simply need to reuse the einj_cxl_ namespace to make it common.
> > 
> 
> I'll be honest; I'm not sure I understand the concern here, but that's probably
> just inexperience on my part. That being said, I don't mind changing it if you
> have any suggestions!
> 

Notice how the CXL subsystem organizes all the ACPI interface concerns
into drivers/cxl/acpi.c. There are some generic callbacks like the
@calc_hb argument to cxl_root_decoder_alloc(), but there are no direct
ties of the CXL core code to ACPI details. This separation allows, in
principle, a non-ACPI platform (like PowerPC OpenFirmware) to support
CXL without needing to unwind a bunch of CXL-ACPI specific stuff.

This "cxl_einj" work is leaking an ACPI specific term "EINJ" into the
core code. The reason I am ok with this is that the ABI is still gated
on CONFIG_ACPI_APEI_EINJ. Also, we still have the option to require that
OpenFirmware error injection just call their user facing ABI "EINJ" as
well, even if it is a different name in the OpenFirmware specification.
To be clear though no one has sent patches for CXL support on anything
other than ACPI based platforms.