userspace-api/fwctl/fwctl.rst

13 software-defined pieces of hardware. The evolution of this approach is largely a
14 reaction to Moore's Law where a chip tape out is now highly expensive, and the
15 chip design is extremely large. Replacing fixed HW logic with a flexible and
16 tightly coupled FW/HW combination is an effective risk mitigation against chip
17 respin. Problems in the HW design can be counteracted in device FW. This is
41 support, and FW-driven functionality that is not well suited to “generic”
46 fwctl is aimed at the common device design pattern where the OS and FW
52 fit into any specific subsystem. For example, a HW RAID controller is primarily
61 fwctl's purpose is to define a common set of limited rules, described below,
73 It is not an avenue to access random kernel internals, or other operating system
78 device the function is permitted to access. For instance, the most complex PCIe
90 For instance a child VM's FW may be within the scope of the hypervisor FW. It is
99     function reset. Access to function & child runtime configuration that is
138 fwctl is not a replacement for device direct access subsystems like uacce or
179 kernel driver. Providing such an implementation is a pre-condition to merging a
182 The goal is to build user space community around some of the shared problems
194 that stretch across all subsystems in the kernel. fwupd is a great example of
207 In many cases a fwctl driver is going to be part of a larger cross-subsystem
215 provided by user space are mapped to the appropriate scope. If the validation is
217 the device, or hardwire the enforcement. If the validation is done in the FW,
243 devices fix them with a FW update, push a kernel patch to parse and block RPC
244 commands or push a kernel patch to block entire firmware versions/devices.
246 While the kernel can always directly parse and restrict RPCs, it is expected
253 The approach described in this document is not a new idea. Direct, or near
254 direct device access has been offered by the kernel in different areas for
255 decades. With more devices wanting to follow this design pattern it is becoming
256 clear that it is not entirely well understood and, more importantly, the
274  - RDMA allows user space drivers to directly push commands to the device
285 driver. Developing good community around useful software in user space is key to