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 31Correct flow of setting up the MAC address (summarized): 32 331. Read from hardware in initialize() function 342. Read from environment in net/eth.c after initialize() 353. The environment variable will be compared to the driver initialized 36 struct eth_device->enetaddr. If they differ, a warning is printed, and the 37 environment variable will be used unchanged. 38 If the environment variable is not set, it will be initialized from 39 eth_device->enetaddr, and a warning will be printed. 404. Program the address into hardware if the following conditions are met: 41 a) The relevant driver has a 'write_addr' function 42 b) The user hasn't set an 'ethmacskip' environment variable 43 c) The address is valid (unicast, not all-zeros) 44 45Previous behavior had the MAC address always being programmed into hardware 46in the device's init() function. 47 48------- 49 Usage 50------- 51 52If the hardware design mandates that the MAC address is stored in some special 53place (like EEPROM etc...), then the board specific init code (such as the 54board-specific misc_init_r() function) is responsible for locating the MAC 55address(es) and initializing the respective environment variable(s) from it. 56Note that this shall be done if, and only if, the environment does not already 57contain these environment variables, i.e. existing variable definitions must 58not be overwritten. 59 60During runtime, the ethernet layer will use the environment variables to sync 61the MAC addresses to the ethernet structures. All ethernet driver code should 62then only use the enetaddr member of the eth_device structure. This is done 63on every network command, so the ethernet copies will stay in sync. 64 65Any other code that wishes to access the MAC address should query the 66environment directly. The helper functions documented below should make 67working with this storage much smoother. 68 69--------- 70 Helpers 71--------- 72 73To assist in the management of these layers, a few helper functions exist. You 74should use these rather than attempt to do any kind of parsing/manipulation 75yourself as many common errors have arisen in the past. 76 77 * void eth_parse_enetaddr(const char *addr, uchar *enetaddr); 78 79Convert a string representation of a MAC address to the binary version. 80char *addr = "00:11:22:33:44:55"; 81uchar enetaddr[6]; 82eth_parse_enetaddr(addr, enetaddr); 83/* enetaddr now equals { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 } */ 84 85 * int eth_getenv_enetaddr(char *name, uchar *enetaddr); 86 87Look up an environment variable and convert the stored address. If the address 88is valid, then the function returns 1. Otherwise, the function returns 0. In 89all cases, the enetaddr memory is initialized. If the env var is not found, 90then it is set to all zeros. The common function is_valid_ethaddr() is used 91to determine address validity. 92uchar enetaddr[6]; 93if (!eth_getenv_enetaddr("ethaddr", enetaddr)) { 94 /* "ethaddr" is not set in the environment */ 95 ... try and setup "ethaddr" in the env ... 96} 97/* enetaddr is now set to the value stored in the ethaddr env var */ 98 99 * int eth_setenv_enetaddr(char *name, const uchar *enetaddr); 100 101Store the MAC address into the named environment variable. The return value is 102the same as the setenv() function. 103uchar enetaddr[6] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 }; 104eth_setenv_enetaddr("ethaddr", enetaddr); 105/* the "ethaddr" env var should now be set to "00:11:22:33:44:55" */ 106 107 * the %pM format modifier 108 109The %pM format modifier can be used with any standard printf function to format 110the binary 6 byte array representation of a MAC address. 111uchar enetaddr[6] = { 0x00, 0x11, 0x22, 0x33, 0x44, 0x55 }; 112printf("The MAC is %pM\n", enetaddr); 113 114char buf[20]; 115sprintf(buf, "%pM", enetaddr); 116/* the buf variable is now set to "00:11:22:33:44:55" */ 117