From a5bde5d8fde8a8cb28e59a672d5ddc5b9c1e7656 Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Wed, 5 Aug 2026 07:52:36 -0700 Subject: workqueue: skip the node_nr_active update for non-unbound workqueues apply_wqattrs_commit() updates node_nr_active->max unconditionally. wq->node_nr_active[] is only allocated for unbound workqueues, so guard the call before per-cpu workqueues start using this path. No functional change: only unbound workqueues reach apply_wqattrs_*() today. Signed-off-by: Breno Leitao Signed-off-by: Tejun Heo --- Documentation/driver-api/fpga/intro.rst | 54 +++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 Documentation/driver-api/fpga/intro.rst (limited to 'Documentation/driver-api/fpga/intro.rst') diff --git a/Documentation/driver-api/fpga/intro.rst b/Documentation/driver-api/fpga/intro.rst new file mode 100644 index 000000000..f54c7dabc --- /dev/null +++ b/Documentation/driver-api/fpga/intro.rst @@ -0,0 +1,54 @@ +Introduction +============ + +The FPGA subsystem supports reprogramming FPGAs dynamically under +Linux. Some of the core intentions of the FPGA subsystems are: + +* The FPGA subsystem is vendor agnostic. + +* The FPGA subsystem separates upper layers (userspace interfaces and + enumeration) from lower layers that know how to program a specific + FPGA. + +* Code should not be shared between upper and lower layers. This + should go without saying. If that seems necessary, there's probably + framework functionality that can be added that will benefit + other users. Write the linux-fpga mailing list and maintainers and + seek out a solution that expands the framework for broad reuse. + +* Generally, when adding code, think of the future. Plan for reuse. + +The framework in the kernel is divided into: + +FPGA Manager +------------ + +If you are adding a new FPGA or a new method of programming an FPGA, +this is the subsystem for you. Low level FPGA manager drivers contain +the knowledge of how to program a specific device. This subsystem +includes the framework in fpga-mgr.c and the low level drivers that +are registered with it. + +FPGA Bridge +----------- + +FPGA Bridges prevent spurious signals from going out of an FPGA or a +region of an FPGA during programming. They are disabled before +programming begins and re-enabled afterwards. An FPGA bridge may be +actual hard hardware that gates a bus to a CPU or a soft ("freeze") +bridge in FPGA fabric that surrounds a partial reconfiguration region +of an FPGA. This subsystem includes fpga-bridge.c and the low level +drivers that are registered with it. + +FPGA Region +----------- + +If you are adding a new interface to the FPGA framework, add it on top +of an FPGA region. + +The FPGA Region framework (fpga-region.c) associates managers and +bridges as reconfigurable regions. A region may refer to the whole +FPGA in full reconfiguration or to a partial reconfiguration region. + +The Device Tree FPGA Region support (of-fpga-region.c) handles +reprogramming FPGAs when device tree overlays are applied. -- cgit v1.3.1