This describes what it is for, devices supported, how to enable for your board in U-Boot, setting up the server, and notes about MAC addresses.
Signed-off-by: Simon Glass sjg@chromium.org --- doc/README.usb | 163 +++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 files changed, 162 insertions(+), 1 deletions(-)
diff --git a/doc/README.usb b/doc/README.usb index 9aa4f62..8693a05 100644 --- a/doc/README.usb +++ b/doc/README.usb @@ -79,4 +79,165 @@ CONFIG_USB_UHCI defines the lowlevel part.A lowlevel part must be defined if using CONFIG_CMD_USB CONFIG_USB_KEYBOARD enables the USB Keyboard CONFIG_USB_STORAGE enables the USB storage devices -CONFIG_USB_HOST_ETHER enables USB ethernet dongle support +CONFIG_USB_HOST_ETHER enables USB ethernet adapter support + + +USB Host Networking +=================== + +If you have a supported USB Ethernet adapter you can use it in U-Boot +to obtain an IP address and load a kernel from a network server. + +USB Host Networking is different from making your board act as a USB +client. In that case your board is pretending to be an Ethernet adapter +and will appear as a network interface to an attached computer. The +connection is via a USB cable with the computer acting as the host. + +With USB Host Networking, your board is the USB host. It controls the +Ethernet adapter to which it is directly connected and the connection to +the outside world is your adapter's Ethernet cable. Your board becomes a +first class network device, able to connect and perform network +operations independently of your computer. + + +Device support +-------------- + +Currently supported devices are listed in the drivers according to +their vendor and product IDs. You can check your device by connecting it +to a Linux machine and typing 'lsusb'. The drivers are in +drivers/usb/eth. + +For example this lsusb output line shows a device with Vendor ID 0x0x95 +and product ID 0x7720: + +Bus 002 Device 010: ID 0b95:7720 ASIX Electronics Corp. AX88772 + +If you look at drivers/usb/eth/asix.c you will see this line within the +supported device list, so we know this adapter is supported. + + { 0x0b95, 0x7720 }, /* Trendnet TU2-ET100 V3.0R */ + +If your adapter is not listed there is a still a chance that it will +work. Try looking up the manufacturer of the chip inside your adapter. +or take the adapter apart and look for chip markings. Then add a line +for your vendor/product ID into the table of the appropriate driver, +build U-Boot and see if it works. If not then there might be differences +between the chip in your adapter and the driver. You could try to get a +datasheet for your device and add support for it to U-Boot. This is not +particularly difficult - you only need to provide support for four basic +functions: init, halt, send and recv. + + +Enabling USB Host Networking +---------------------------- + +The normal U-Boot commands are used with USB networking, but you must +start USB first. For example: + +usb start +setenv bootfile /tftpboot/uImage +setenv autoload y +bootp + + +(The autoload option makes bootp automatically load the boot file.) + +To enable USB Host Ethernet in U-Boot, your platform must of course +support USB with CONFIG_CMD_USB enabled and working. You will need to +add some config settings to your board header file: + +#define CONFIG_USB_HOST_ETHER /* Enable USB Ethernet adapters */ +#define CONFIG_USB_ETHER_ASIX /* Asix, or whatever driver(s) you want */ + +You will also want to enable the network commands: + +#define CONFIG_CMD_NET +#define CONFIG_NET_MULTI +#define CONFIG_CMD_PING +#define CONFIG_CMD_DHCP + +and some bootp options, which tell your board to obtain its subnet, +gateway IP, host name and boot path from the bootp/dhcp server: + +#define CONFIG_BOOTP_SUBNETMASK +#define CONFIG_BOOTP_GATEWAY +#define CONFIG_BOOTP_HOSTNAME +#define CONFIG_BOOTP_BOOTPATH + +You should also set the default IP address of your board and the server +as well as the default file to load when a 'bootp' command is issued. + +#define CONFIG_IPADDR 10.0.0.2 +#define CONFIG_SERVERIP 10.0.0.1 +#define CONFIG_BOOTFILE uImage + + +The 'usb start' command should identify the adapter something like this: + +CrOS> usb start +(Re)start USB... +USB EHCI 1.00 +scanning bus for devices... 3 USB Device(s) found + scanning bus for storage devices... 0 Storage Device(s) found + scanning bus for ethernet devices... 1 Ethernet Device(s) found +CrOS> print ethact +ethact=asx0 + +You can see that it found an ethernet device and we can print out the +device name (asx0 in this case). + +Then 'bootp' should use it to obtain an IP address from DHCP, perhaps +something like this: + +CrOS> bootp +Waiting for Ethernet connection... done. +BOOTP broadcast 1 +BOOTP broadcast 2 +DHCP client bound to address 172.22.73.81 +Using asx0 device +TFTP from server 172.22.72.144; our IP address is 172.22.73.81 +Filename '/tftpboot/uImage-sjg-seaboard-261347'. +Load address: 0x40c000 +Loading: ################################################################# + ################################################################# + ################################################################# + ################################################ +done +Bytes transferred = 3557464 (364858 hex) +CrOS> + + +MAC Addresses +------------- + +Most Ethernet dongles have a built-in MAC address which is unique in the +world. This is important so that devices on the network can be +distinguised from each other. MAC address conflicts are evil and +generally result in strange and eratic behaviour. + +Some boards have USB Ethernet chips on-board, and these sometimes do not +have an assigned MAC address. In this case it is up to you to assign +one which is unique. You should obtain a valid MAC address from a range +assigned to you before you ship the product. + +Built-in Ethernet adapters support setting the MAC address by means of +an ethaddr environment variable for each interface (ethaddr, eth1addr, +eth2addr). There is similar support on the USB network side, using the +names usbethaddr, usbeth1addr, etc. They are kept separate since we +don't want a USB device taking the MAC address of a built-in device or +vice versa. + +So if your USB Ethernet chip doesn't have a MAC address available then +you must set usbethaddr to a suitable MAC address. At the time of +writing this functionality is only supported by the SMSC driver. + + +Server Setup +------------ + +For setting up the server side (dhcpd, tftpd, nfsd) you might find this +Chromium OS page useful: + +http://www.chromium.org/network-based-development +