u-boot/tools/env/README

This is a demo implementation of a Linux command line tool to access
the U-Boot's environment variables.

For the run-time utiltity configuration uncomment the line
#define CONFIG_FILE  "/etc/fw_env.config"
in fw_env.h.

For building against older versions of the MTD headers (meaning before
v2.6.8-rc1) it is required to pass the argument "MTD_VERSION=old" to
make.

See comments in the fw_env.config file for definitions for the
particular board.

Configuration can also be done via #defines in the fw_env.h file. The
following lines are relevant:

#define HAVE_REDUND	/* For systems with 2 env sectors */
#define DEVICE1_NAME	"/dev/mtd1"
#define DEVICE2_NAME	"/dev/mtd2"
#define DEVICE1_OFFSET    0x0000
#define ENV1_SIZE         0x4000
#define DEVICE1_ESIZE     0x4000
#define DEVICE2_OFFSET    0x0000
#define ENV2_SIZE         0x4000
#define DEVICE2_ESIZE     0x4000

Current configuration matches the environment layout of the TRAB
board.

Un-define HAVE_REDUND, if you want to use the utlities on a system
that does not have support for redundant environment enabled.
If HAVE_REDUND is undefined, DEVICE2_NAME is ignored,
as is ENV2_SIZE and DEVICE2_ESIZE.

The DEVICEx_NAME constants define which MTD character devices are to
be used to access the environment.

The DEVICEx_OFFSET constants define the environment offset within the
MTD character device.

ENVx_SIZE defines the size in bytes taken by the environment, which
may be less then flash sector size, if the environment takes less
then 1 sector.

DEVICEx_ESIZE defines the size of the first sector in the flash
partition where the environment resides.