# 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'. config CXL_MEM_RAW_COMMANDS bool "RAW Command Interface for Memory Devices" depends on CXL_MEM help Enable CXL RAW command interface. The CXL driver ioctl interface may assign a kernel ioctl command number for each specification defined opcode. At any given point in time the number of opcodes that the specification defines and a device may implement may exceed the kernel's set of associated ioctl function numbers. The mismatch is either by omission, specification is too new, or by design. When prototyping new hardware, or developing / debugging the driver it is useful to be able to submit any possible command to the hardware, even commands that may crash the kernel due to their potential impact to memory currently in use by the kernel. If developing CXL hardware or the driver say Y, otherwise say N. endif