From 9cc63f8bcd560c760d0b12e15bba8f81c86237cf Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 14 Aug 2026 15:43:51 -0700 Subject: Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEAD Changes: Make expedited grace periods expedite normal RCU callbacks Miscellaneous fixes: * Improve diagnostic output with character task states. * Mark accesses to inform KCSAN of concurrency design. * Move from kmalloc() to kmalloc_obj(). * Documentation updates. * Improve handling of RCU deferred quiescent states. * Clean up unused function arguments and structure fields. * Reduce show_rcu_gp_kthreads() stack space. Tasks RCU updates: * Clean up after SRCU re-implementation of Tasks Trace RCU. * Mark accesses to inform KCSAN of concurrency design. * Add ->lazy_timer status to diagnostic output. * Remove an unnecessary memory barrier. * Fix a data race, courtesy of KCSAN. * Documentation updates. * Convert cond_resched_tasks_rcu_qs() from macro to static inline function. SRCU updates: * Add Rust helpers for SRCU. * Avoid losing queued work at cleanup_srcu_struct() time. Torture-test updates: * Preparation work for immediate RCU priority deboosting. * Test RCU readers from real interrupt handlers (as opposed to softirq). * Simplify code through use of cpumask_next_wrap(). * Improve diagnostic output with character task states. * Add rcutorture.nwriters parameter to allow lightweight stall testing, and rcutorture.stall_only to make doing so easier. * Test an RCU Tasks Trace grace period implying an RCU grace period. * Make RCU Tasks Trace torturing track reader batches. * Fix a data race, courtesy of KCSAN. * Plug a shuffle_tmp_mask memory leak on kthread spawn failure. --- .../firmware/firmware-usage-guidelines.rst | 49 ++++++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 Documentation/driver-api/firmware/firmware-usage-guidelines.rst (limited to 'Documentation/driver-api/firmware/firmware-usage-guidelines.rst') diff --git a/Documentation/driver-api/firmware/firmware-usage-guidelines.rst b/Documentation/driver-api/firmware/firmware-usage-guidelines.rst new file mode 100644 index 000000000..336e91228 --- /dev/null +++ b/Documentation/driver-api/firmware/firmware-usage-guidelines.rst @@ -0,0 +1,49 @@ +=================== +Firmware Guidelines +=================== + +Users switching to a newer kernel should *not* have to install newer +firmware files to keep their hardware working. At the same time updated +firmware files must not cause any regressions for users of older kernel +releases. + +Drivers that use firmware from linux-firmware should follow the rules in +this guide. (Where there is limited control of the firmware, +i.e. company doesn't support Linux, firmwares sourced from misc places, +then of course these rules will not apply strictly.) + +* Firmware files shall be designed in a way that it allows checking for + firmware ABI version changes. It is recommended that firmware files be + versioned with at least a major/minor version. It is suggested that + the firmware files in linux-firmware be named with some device + specific name, and just the major version. The firmware version should + be stored in the firmware header, or as an exception, as part of the + firmware file name, in order to let the driver detact any non-ABI + fixes/changes. The firmware files in linux-firmware should be + overwritten with the newest compatible major version. Newer major + version firmware shall remain compatible with all kernels that load + that major number. + +* If the kernel support for the hardware is normally inactive, or the + hardware isn't available for public consumption, this can + be ignored, until the first kernel release that enables that hardware. + This means no major version bumps without the kernel retaining + backwards compatibility for the older major versions. Minor version + bumps should not introduce new features that newer kernels depend on + non-optionally. + +* If a security fix needs lockstep firmware and kernel fixes in order to + be successful, then all supported major versions in the linux-firmware + repo that are required by currently supported stable/LTS kernels, + should be updated with the security fix. The kernel patches should + detect if the firmware is new enough to declare if the security issue + is fixed. All communications around security fixes should point at + both the firmware and kernel fixes. If a security fix requires + deprecating old major versions, then this should only be done as a + last option, and be stated clearly in all communications. + +* Firmware files that affect the User API (UAPI) shall not introduce + changes that break existing userspace programs. Updates to such firmware + must ensure backward compatibility with existing userspace applications. + This includes maintaining consistent interfaces and behaviors that + userspace programs rely on. -- cgit v1.3.1