Comment 0 for bug 2028550

[ Impact ]

 * To ensure reliable dist-upgrades in case of partial upgrades or upgrade failures, it is desirable for LTS GA kernel to support features that next-LTS GA kernel will rely on.

 * Specifically it is being discussed to switch linux-firmware to ZSTD compressed one

 * To ensure that failed dist-upgrades can still boot after-partial upgrade it is desirable to suppport zstd compressed firmware

[ Test Plan ]

 * Boot new build of GA linux kernel with CONFIG_FW_LOADER_COMPRESS_ZSTD

 * Check that existing firmware files loaded on a given machine can be compressed with zstd and still loaded by this kernel

 * Check that depmod / initramfs-tools all support .zst compressed firmware

[ Where problems could occur ]

 * Once this is inroduced in jammy-GA kernel it may cripple into focal-hwe kernels too, and people may start relying on this feature despite not universally supported by all other focal kernels. This should be trivial to catch in SRUs for example, do not accept SRUs of firmwares that ship themselves as .zst in Jammy and lower.

[ Other Info ]

 * See https://lists.ubuntu.com/archives/ubuntu-devel/2023-July/042652.html