The abr-shim driver uses //src/firmware/lib/abr to reboot to recovery on devices that don't support PSCI reset arguments. It does this by binding to the GPT partition that contains ABR metadata based on the type GUID and setting the one-shot recovery flag during the driver suspend hook. abr-shim implements fuchsia.hardware.block.BlockImpl and fuchsia.hardware.block.partition.BlockPartition and forwards calls from children to its parent. Block ops received during the suspend hook are completed with ZX_ERR_CANCELED.
Boards that need to use abr-shim should pass fuchsia.hardware.gpt.metadata.GptInfo with block_driver_should_ignore_device set for the ABR partition as metadata to the storage driver with DEVICE_METADATA_GPT_INFO.