1 2This is a demo implementation of a Linux command line tool to access 3the U-Boot's environment variables. 4 5In order to cross-compile fw_printenv, run 6 make CROSS_COMPILE=<your cross-compiler prefix> env 7in the root directory of the U-Boot distribution. For example, 8 make CROSS_COMPILE=arm-linux- env 9 10For the run-time utility configuration uncomment the line 11#define CONFIG_FILE "/etc/fw_env.config" 12in fw_env.h. 13 14For building against older versions of the MTD headers (meaning before 15v2.6.8-rc1) it is required to pass the argument "MTD_VERSION=old" to 16make. 17 18See comments in the fw_env.config file for definitions for the 19particular board. 20 21Configuration can also be done via #defines in the fw_env.h file. The 22following lines are relevant: 23 24#define HAVE_REDUND /* For systems with 2 env sectors */ 25#define DEVICE1_NAME "/dev/mtd1" 26#define DEVICE2_NAME "/dev/mtd2" 27#define DEVICE1_OFFSET 0x0000 28#define ENV1_SIZE 0x4000 29#define DEVICE1_ESIZE 0x4000 30#define DEVICE1_ENVSECTORS 2 31#define DEVICE2_OFFSET 0x0000 32#define ENV2_SIZE 0x4000 33#define DEVICE2_ESIZE 0x4000 34#define DEVICE2_ENVSECTORS 2 35 36Un-define HAVE_REDUND, if you want to use the utilities on a system 37that does not have support for redundant environment enabled. 38If HAVE_REDUND is undefined, DEVICE2_NAME is ignored, 39as is ENV2_SIZE and DEVICE2_ESIZE. 40 41The DEVICEx_NAME constants define which MTD character devices are to 42be used to access the environment. 43 44The DEVICEx_OFFSET constants define the environment offset within the 45MTD character device. 46 47ENVx_SIZE defines the size in bytes taken by the environment, which 48may be less then flash sector size, if the environment takes less 49then 1 sector. 50 51DEVICEx_ESIZE defines the size of the first sector in the flash 52partition where the environment resides. 53 54DEVICEx_ENVSECTORS defines the number of sectors that may be used for 55this environment instance. On NAND this is used to limit the range 56within which bad blocks are skipped, on NOR it is not used. 57 58To prevent losing changes to the environment and to prevent confusing the MTD 59drivers, a lock file at /var/lock/fw_printenv.lock is used to serialize access 60to the environment. 61