xref: /openbmc/u-boot/tools/env/README (revision c0dcece7)
1
2This is a demo implementation of a Linux command line tool to access
3the U-Boot's environment variables.
4
5In the current version, there is an issue in cross-compilation.
6In order to cross-compile fw_printenv, run
7    make HOSTCC=<your CC cross-compiler> env
8in the root directory of the U-Boot distribution. For example,
9    make HOSTCC=arm-linux-gcc env
10
11For the run-time utility configuration uncomment the line
12#define CONFIG_FILE  "/etc/fw_env.config"
13in fw_env.h.
14
15For building against older versions of the MTD headers (meaning before
16v2.6.8-rc1) it is required to pass the argument "MTD_VERSION=old" to
17make.
18
19See comments in the fw_env.config file for definitions for the
20particular board.
21
22Configuration can also be done via #defines in the fw_env.h file. The
23following lines are relevant:
24
25#define HAVE_REDUND	/* For systems with 2 env sectors */
26#define DEVICE1_NAME	"/dev/mtd1"
27#define DEVICE2_NAME	"/dev/mtd2"
28#define DEVICE1_OFFSET    0x0000
29#define ENV1_SIZE         0x4000
30#define DEVICE1_ESIZE     0x4000
31#define DEVICE1_ENVSECTORS     2
32#define DEVICE2_OFFSET    0x0000
33#define ENV2_SIZE         0x4000
34#define DEVICE2_ESIZE     0x4000
35#define DEVICE2_ENVSECTORS     2
36
37Un-define HAVE_REDUND, if you want to use the utilities on a system
38that does not have support for redundant environment enabled.
39If HAVE_REDUND is undefined, DEVICE2_NAME is ignored,
40as is ENV2_SIZE and DEVICE2_ESIZE.
41
42The DEVICEx_NAME constants define which MTD character devices are to
43be used to access the environment.
44
45The DEVICEx_OFFSET constants define the environment offset within the
46MTD character device.
47
48ENVx_SIZE defines the size in bytes taken by the environment, which
49may be less then flash sector size, if the environment takes less
50then 1 sector.
51
52DEVICEx_ESIZE defines the size of the first sector in the flash
53partition where the environment resides.
54
55DEVICEx_ENVSECTORS defines the number of sectors that may be used for
56this environment instance. On NAND this is used to limit the range
57within which bad blocks are skipped, on NOR it is not used.
58
59To prevent losing changes to the environment and to prevent confusing the MTD
60drivers, a lock file at /var/lock/fw_printenv.lock is used to serialize access
61to the environment.
62