Interface¶

The primary means of communicating with the Switchtec management firmware isthrough the Memory-mapped Remote Procedure Call (MRPC) interface.Commands are submitted to the interface with a 4-byte commandidentifier and up to 1KB of command specific data. The firmware willrespond with a 4-byte return code and up to 1KB of command-specificdata. The interface only processes a single command at a time.

Userspace Interface¶

The MRPC interface will be exposed to userspace through a simple chardevice: /dev/switchtec#, one for each management endpoint in the system.

The char device has the following semantics:

• A write must consist of at least 4 bytes and no more than 1028 bytes.The first 4 bytes will be interpreted as the Command ID and theremainder will be used as the input data. A write will send thecommand to the firmware to begin processing.
• Each write must be followed by exactly one read. Any double write willproduce an error and any read that doesn’t follow a write willproduce an error.
• A read will block until the firmware completes the command and returnthe 4-byte Command Return Value plus up to 1024 bytes of outputdata. (The length will be specified by the size parameter of the readcall – reading less than 4 bytes will produce an error.)
• The poll call will also be supported for userspace applications thatneed to do other things while waiting for the command to complete.

The following IOCTLs are also supported by the device:

• SWITCHTEC_IOCTL_FLASH_INFO - Retrieve firmware length and numberof partitions in the device.
• SWITCHTEC_IOCTL_FLASH_PART_INFO - Retrieve address and lengeth forany specified partition in flash.
• SWITCHTEC_IOCTL_EVENT_SUMMARY - Read a structure of bitmapsindicating all uncleared events.
• SWITCHTEC_IOCTL_EVENT_CTL - Get the current count, clear and set flagsfor any event. This ioctl takes in a switchtec_ioctl_event_ctl structwith the event_id, index and flags set (index being the partition or PFFnumber for non-global events). It returns whether the event hasoccurred, the number of times and any event specific data. The flagscan be used to clear the count or enable and disable actions tohappen when the event occurs.By using the SWITCHTEC_IOCTL_EVENT_FLAG_EN_POLL flag,you can set an event to trigger a poll command to return withPOLLPRI. In this way, userspace can wait for events to occur.
• SWITCHTEC_IOCTL_PFF_TO_PORT and SWITCHTEC_IOCTL_PORT_TO_PFF convertbetween PCI Function Framework number (used by the event system)and Switchtec Logic Port ID and Partition number (which is moreuser friendly).

Non-Transparent Bridge (NTB) Driver¶

An NTB hardware driver is provided for the Switchtec hardware inntb_hw_switchtec. Currently, it only supports switches configured withexactly 2 NT partitions and zero or more non-NT partitions. It also requiresthe following configuration settings:

• Both NT partitions must be able to access each other’s GAS spaces.Thus, the bits in the GAS Access Vector under Management Settingsmust be set to support this.
• Kernel configuration MUST include support for NTB (CONFIG_NTB needsto be set)

NT EP BAR 2 will be dynamically configured as a Direct Window, andthe configuration file does not need to configure it explicitly.

Please refer to Documentation/driver-api/ntb.rst in Linux source tree for an overallunderstanding of the Linux NTB stack. ntb_hw_switchtec works as an NTBHardware Driver in this stack.