Side channel access through USB streams
A system may provide side channel access of a Universal Serial Bus (USB) device using USB streams. The system may include a USB interface with a USB device controller, an internal bus, a logical unit number (LUN) arbiter coupled between the USB controller and the internal bus, and a secondary interface coupled with the LUN arbiter. The system may include a plurality of storage devices coupled to the internal bus. The system may provide access to the storage devices via both the USB device controller and the secondary interface. The LUN arbiter may accept a plurality of USB streams (e.g., storage device access requests) from the USB device controller and at least one additional USB stream (e.g., storage device access request) from the secondary interface. The LUN arbiter may determine a priority of access between USB streams originating from the USB device controller and the secondary interface.
1. A system comprising:
a USB device controller;
an internal bus;
a side channel interface unit;
a logical unit number (LUN) arbiter coupled between (i) the USB device controller and the internal bus and (ii) the side channel interface unit and the internal bus;
at least one hardware controller coupled to the internal bus; and
at least one processor configured to:
generate first and second USB packets for accessing the at least one hardware controller;
transmit the first USB packet to the USB device controller via a USB interface; and
transmit the second USB packet to the side channel interface unit by tunneling the second USB packet over a side channel interface communication protocol;
wherein the USB device controller forwards the first USB packet to the LUN arbiter as a first USB stream, the side channel interface unit forwards the second USB packet to the LUN arbiter as a second USB stream, and the LUN arbiter determines an access priority between the first and second USB streams.
2. The system according to claim 1 , wherein the at least one hardware controller is accessed in response to the first and second USB packets.
3. The system according to claim 1 , wherein the at least one hardware controller is a memory card controller.
4. The system according to claim 1 , wherein the internal bus is a Small Computer System Interface (SCSI) bus and the at least one hardware controller is coupled to the internal bus via a SCSI command processing unit.
5. The system according to claim 1 , wherein the side channel interface communication protocol is one of: a Serial Peripheral Interface (SPI) protocol, an Inter-Integrated Circuit (I2C) interface protocol, or a Universal asynchronous receiver/transmitter (UART) interface protocol.
6. The system according to claim 1 , wherein the side channel interface unit forwards the second USB packet to the LUN arbiter using a FIFO.
7. The system according to claim 1 , wherein the LUN arbiter is configured to accept a plurality of USB streams from the USB device controller and at least one additional stream from the side channel interface unit.
8. The system according to claim 1 , wherein the first USB packet is generated by a first processor of the at least one processors, and the second USB packet is generated by a second processor of the at least one processors.
9. The system according to claim 8 , wherein the first processor is part of a first hardware unit, the second processor is part of a second hardware unit, and the USB device controller is part of a third hardware unit.