/sys/class/fpga_bridge
| Field | Value |
|---|---|
| Subsystem | FPGA Bridge core, drivers/fpga/fpga-bridge.c (class fpga_bridge_class, device name br%d) |
| Config gate | CONFIG_FPGA_BRIDGE, “FPGA Bridge Framework” (drivers/fpga/Kconfig) |
| ABI documentation | Documentation/ABI/testing/sysfs-class-fpga-bridge (2 What: entries) |
| Since | January 2016, KernelVersion 4.5 (both entries) |
| Live (5.10.134 host) | none observed (class absent from the cached 46-class enumeration) |
| Ledger ID | SYSC-fpga_bridge |
What it represents
One device per FPGA bridge driver registered with fpga_bridge_register(). A bridge is the switchable fabric segment between an FPGA and the rest of the system (buses, memory paths); it is disabled while the FPGA is reprogrammed and re-enabled afterwards so that live traffic does not cross a partially configured fabric.
Relationship to the device model
Bridge devices hang off the hardware device their driver binds to. The FPGA region core (fpga_region.md) locates bridges by device-tree node and by device via class lookups (class_find_device_by_of_node, drivers/fpga/fpga-bridge.c), then enables or disables them around manager programming operations.
Attributes (representative; source per row)
| Attribute | R/W | Meaning (source: ABI testing/sysfs-class-fpga-bridge; class code fpga-bridge.c) |
|---|---|---|
name | RO | Name of the low level FPGA bridge driver |
state | RO | Bridge state shown as “enabled” or “disabled” |
Safety and writes
Both attributes are read-only. Enabling and disabling bridges happens inside the region programming flow through the fpga_bridge API; there is no sysfs write path, so no user action can leave a bridge open across a reconfiguration. None observed on the read-only container host.
References
- Documentation/ABI/testing/sysfs-class-fpga-bridge
- drivers/fpga/fpga-bridge.c (fetched from torvalds/linux master into source-cache)
- sysfs overview, ledger, fpga_manager, fpga_region