1*321eaf31SDave Airlie=================== 2*321eaf31SDave AirlieFirmware Guidelines 3*321eaf31SDave Airlie=================== 4*321eaf31SDave Airlie 5*321eaf31SDave AirlieUsers switching to a newer kernel should *not* have to install newer 6*321eaf31SDave Airliefirmware files to keep their hardware working. At the same time updated 7*321eaf31SDave Airliefirmware files must not cause any regressions for users of older kernel 8*321eaf31SDave Airliereleases. 9*321eaf31SDave Airlie 10*321eaf31SDave AirlieDrivers that use firmware from linux-firmware should follow the rules in 11*321eaf31SDave Airliethis guide. (Where there is limited control of the firmware, 12*321eaf31SDave Airliei.e. company doesn't support Linux, firmwares sourced from misc places, 13*321eaf31SDave Airliethen of course these rules will not apply strictly.) 14*321eaf31SDave Airlie 15*321eaf31SDave Airlie* Firmware files shall be designed in a way that it allows checking for 16*321eaf31SDave Airlie firmware ABI version changes. It is recommended that firmware files be 17*321eaf31SDave Airlie versioned with at least a major/minor version. It is suggested that 18*321eaf31SDave Airlie the firmware files in linux-firmware be named with some device 19*321eaf31SDave Airlie specific name, and just the major version. The firmware version should 20*321eaf31SDave Airlie be stored in the firmware header, or as an exception, as part of the 21*321eaf31SDave Airlie firmware file name, in order to let the driver detact any non-ABI 22*321eaf31SDave Airlie fixes/changes. The firmware files in linux-firmware should be 23*321eaf31SDave Airlie overwritten with the newest compatible major version. Newer major 24*321eaf31SDave Airlie version firmware shall remain compatible with all kernels that load 25*321eaf31SDave Airlie that major number. 26*321eaf31SDave Airlie 27*321eaf31SDave Airlie* If the kernel support for the hardware is normally inactive, or the 28*321eaf31SDave Airlie hardware isn't available for public consumption, this can 29*321eaf31SDave Airlie be ignored, until the first kernel release that enables that hardware. 30*321eaf31SDave Airlie This means no major version bumps without the kernel retaining 31*321eaf31SDave Airlie backwards compatibility for the older major versions. Minor version 32*321eaf31SDave Airlie bumps should not introduce new features that newer kernels depend on 33*321eaf31SDave Airlie non-optionally. 34*321eaf31SDave Airlie 35*321eaf31SDave Airlie* If a security fix needs lockstep firmware and kernel fixes in order to 36*321eaf31SDave Airlie be successful, then all supported major versions in the linux-firmware 37*321eaf31SDave Airlie repo that are required by currently supported stable/LTS kernels, 38*321eaf31SDave Airlie should be updated with the security fix. The kernel patches should 39*321eaf31SDave Airlie detect if the firmware is new enough to declare if the security issue 40*321eaf31SDave Airlie is fixed. All communications around security fixes should point at 41*321eaf31SDave Airlie both the firmware and kernel fixes. If a security fix requires 42*321eaf31SDave Airlie deprecating old major versions, then this should only be done as a 43*321eaf31SDave Airlie last option, and be stated clearly in all communications. 44*321eaf31SDave Airlie 45