1--------------------------------- 2 Ethernet Address (MAC) Handling 3--------------------------------- 4 5There are a variety of places in U-Boot where the MAC address is used, parsed, 6and stored. This document covers proper usage of each location and the moving 7of data between them. 8 9----------- 10 Locations 11----------- 12 13Here are the places where MAC addresses might be stored: 14 15 - board-specific location (eeprom, dedicated flash, ...) 16 Note: only used when mandatory due to hardware design etc... 17 18 - environment ("ethaddr", "eth1addr", ...) (see CONFIG_ETHADDR) 19 Note: this is the preferred way to permanently store MAC addresses 20 21 - ethernet data (struct eth_device -> enetaddr) 22 Note: these are temporary copies of the MAC address which exist only 23 after the respective init steps have run and only to make usage 24 in other places easier (to avoid constant env lookup/parsing) 25 26 - struct bd_info and/or device tree 27 Note: these are temporary copies of the MAC address only for the 28 purpose of passing this information to an OS kernel we are about 29 to boot 30 31------- 32 Usage 33------- 34 35If the hardware design mandates that the MAC address is stored in some special 36place (like EEPROM etc...), then the board specific init code (such as the 37board-specific misc_init_r() function) is responsible for locating the MAC 38address(es) and initializing the respective environment variable(s) from it. 39Note that this shall be done if, and only if, the environment does not already 40contain these environment variables, i.e. existing variable definitions must 41not be overwritten. 42 43During runtime, the ethernet layer will use the environment variables to sync 44the MAC addresses to the ethernet structures. All ethernet driver code should 45then only use the enetaddr member of the eth_device structure. This is done 46on every network command, so the ethernet copies will stay in sync. 47 48Any other code that wishes to access the MAC address should query the 49environment directly. The helper functions documented below should make 50working with this storage much smoother. 51 52--------- 53 Helpers 54--------- 55 56To assist in the management of these layers, a few helper functions exist. You 57should use these rather than attempt to do any kind of parsing/manipulation 58yourself as many common errors have arisen in the past. 59 60 * void eth_parse_enetaddr(const char *addr, uchar *enetaddr); 61 62Convert a string representation of a MAC address to the binary version. 63char *addr = "00:11:22:33:44:55"; 64uchar enetaddr[6]; 65eth_parse_enetaddr(addr, enetaddr); 66/* enetaddr now equals { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 } */ 67 68 * int eth_getenv_enetaddr(char *name, uchar *enetaddr); 69 70Look up an environment variable and convert the stored address. If the address 71is valid, then the function returns 1. Otherwise, the function returns 0. In 72all cases, the enetaddr memory is initialized. If the env var is not found, 73then it is set to all zeros. The common function is_valid_ether_addr() is used 74to determine address validity. 75uchar enetaddr[6]; 76if (!eth_getenv_enetaddr("ethaddr", enetaddr)) { 77 /* "ethaddr" is not set in the environment */ 78 ... try and setup "ethaddr" in the env ... 79} 80/* enetaddr is now set to the value stored in the ethaddr env var */ 81 82 * int eth_setenv_enetaddr(char *name, const uchar *enetaddr); 83 84Store the MAC address into the named environment variable. The return value is 85the same as the setenv() function. 86uchar enetaddr[6] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 }; 87eth_setenv_enetaddr("ethaddr", enetaddr); 88/* the "ethaddr" env var should now be set to "00:11:22:33:44:55" */ 89 90 * the %pM format modifier 91 92The %pM format modifier can be used with any standard printf function to format 93the binary 6 byte array representation of a MAC address. 94uchar enetaddr[6] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 }; 95printf("The MAC is %pM\n", enetaddr); 96 97char buf[20]; 98sprintf(buf, "%pM", enetaddr); 99/* the buf variable is now set to "00:11:22:33:44:55" */ 100