# SPDX-License-Identifier: GPL-2.0-only menuconfig CXL_BUS tristate "CXL (Compute Express Link) Devices Support" depends on PCI help CXL is a bus that is electrically compatible with PCI Express, but layers three protocols on that signalling (CXL.io, CXL.cache, and CXL.mem). The CXL.cache protocol allows devices to hold cachelines locally, the CXL.mem protocol allows devices to be fully coherent memory targets, the CXL.io protocol is equivalent to PCI Express. Say 'y' to enable support for the configuration and management of devices supporting these protocols. if CXL_BUS config CXL_MEM tristate "CXL.mem: Memory Devices" help The CXL.mem protocol allows a device to act as a provider of "System RAM" and/or "Persistent Memory" that is fully coherent as if the memory was attached to the typical CPU memory controller. Say 'y/m' to enable a driver (named "cxl_mem.ko" when built as a module) that will attach to CXL.mem devices for configuration, provisioning, and health monitoring. This driver is required for dynamic provisioning of CXL.mem attached memory which is a prerequisite for persistent memory support. Typically volatile memory is mapped by platform firmware and included in the platform memory map, but in some cases the OS is responsible for mapping that memory. See Chapter 2.3 Type 3 CXL Device in the CXL 2.0 specification. If unsure say 'm'. endif