can_backends
Overview
Assembles the CAN backends into one registry. It sits above all of them so that can, which they are written against, does not have to know they exist: putting make_default_registry in can would make a library that hands out a loopback channel depend on libusb. It is small enough that the split costs nothing and keeps the dependency arrows pointing one way.
There is no logic of its own here and nothing that opens hardware. It links can, can_motec, can_pcan, can_socketcan and can_trc, and a caller that links this gets all of them. The caller is can_bridge.
Public headers
| Header | |
|---|---|
can_backends/registry.h | DefaultRegistryOptions, one options struct per backend plus an include* flag each, and make_default_registry. |
Using it
Link the CMake target can_backends. The bridge fills the options from its config and opens channels by the strings in its channel list:
can::DefaultRegistryOptions registryOptions;
registryOptions.pcan.detachKernelDriver = config.pcanDetachKernelDriver;
registryOptions.trc.speed = config.trcReplaySpeed;
registryOptions.trc.paced = config.trcReplayPaced;
auto registry = can::make_default_registry(registryOptions);
auto opened = registry.open(channelConfig.device, open); // "pcan:0/1", "trc:/logs/run.trc/2"
Behaviour worth knowing
Backends are registered in the order PCAN, MoTeC, SocketCAN, virtual, trace. The order decides only what Registry::enumerate() lists first, so real hardware comes before the loopback and can_bridge --list puts the thing that was plugged in at the top.
The include* flags leave a backend out entirely, which is what a test wants for deterministic behaviour on a machine that happens to have a dongle plugged in. The per-backend options are backend-wide, not per channel: a trace replay speed applies to every trc: channel opened from this registry, matching how PcanOptions reaches the PCAN backend.
Tests
None of its own. The one function is exercised by the bridge node’s tests and by every backend’s own test target; see the pages for can, can_pcan, can_socketcan and can_trc.