linux/Documentation/driver-api/cxl/index.rst
Dan Williams 7ac6612d6b Documentation/driver-api/cxl: Introduce conventions.rst
There exists shipping platforms that bend, break, or otherwise lean on
ambiguities in the CXL specification. Without driver changes to accommodate
these deviations, end users are left without CXL subsystem RAS features.
Specifically, provisioning, error translation, and other flows require the
CXL subsystem to understand the platforms CXL topology beyond undecorated
memory address ranges.

Those isolated compatibility problems risk growing into deeper upstream
maintenance burden if different platform vendors arrive at diverging
solutions. For example, there are multiple options for resolving
low-memory-mmio intersecting large-interleave-ways CXL windows. Linux
should only entertain one solution to that problem.

Now, with the ACPI Specification Working Group, situations like this would
be resolved with the "Code First ECN" process to codify Linux expectations
in a specification. In the absence of such a process for the CXL
specification, create a file in Linux documentation to detail the
motivations, assumptions, tradeoffs, and proposals for amending
specification language.

The goal is to capture the issues such that platform vendors arrive at
compatible solutions for these problems and serve as a repository for
potential specification updates. The expectation is to update
conventions.rst along with CXL subsystem code changes to accommodate the
platform topology.

[ dj: Rebased against v6.16-rc1 ]

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Robert Richter <rrichter@amd.com>
Link: https://patch.msgid.link/20250603185254.3730099-1-dan.j.williams@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
2025-06-30 16:36:06 -07:00

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.. SPDX-License-Identifier: GPL-2.0
====================
Compute Express Link
====================
CXL device configuration has a complex handoff between platform (Hardware,
BIOS, EFI), OS (early boot, core kernel, driver), and user policy decisions
that have impacts on each other. The docs here break up configurations steps.
.. toctree::
:maxdepth: 2
:caption: Overview
theory-of-operation
maturity-map
conventions
.. toctree::
:maxdepth: 2
:caption: Device Reference
devices/device-types
.. toctree::
:maxdepth: 2
:caption: Platform Configuration
platform/bios-and-efi
platform/acpi
platform/cdat
platform/example-configs
.. toctree::
:maxdepth: 2
:caption: Linux Kernel Configuration
linux/overview
linux/early-boot
linux/cxl-driver
linux/dax-driver
linux/memory-hotplug
linux/access-coordinates
.. toctree::
:maxdepth: 2
:caption: Memory Allocation
allocation/dax
allocation/page-allocator
allocation/reclaim
allocation/hugepages.rst
.. only:: subproject and html