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This is a demo implementation of a Linux command line tool to access
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the U-Boot's environment variables.
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In order to cross-compile fw_printenv, run
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make CROSS_COMPILE=<your cross-compiler prefix> envtools
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in the root directory of the U-Boot distribution. For example,
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make CROSS_COMPILE=arm-linux- envtools
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You should then create a symlink from fw_setenv to fw_printenv. They use
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the same program and its function depends on its basename.
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For the run-time utility configuration uncomment the line
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#define CONFIG_FILE "/etc/fw_env.config"
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in fw_env.h.
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For building against older versions of the MTD headers (meaning before
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v2.6.8-rc1) it is required to pass the argument "MTD_VERSION=old" to
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make.
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See comments in the fw_env.config file for definitions for the
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particular board.
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Configuration can also be done via #defines in the fw_env.h file. The
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following lines are relevant:
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#define HAVE_REDUND /* For systems with 2 env sectors */
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#define DEVICE1_NAME "/dev/mtd1"
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#define DEVICE2_NAME "/dev/mtd2"
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#define DEVICE1_OFFSET 0x0000
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#define ENV1_SIZE 0x4000
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#define DEVICE1_ESIZE 0x4000
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#define DEVICE1_ENVSECTORS 2
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#define DEVICE2_OFFSET 0x0000
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#define ENV2_SIZE 0x4000
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#define DEVICE2_ESIZE 0x4000
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#define DEVICE2_ENVSECTORS 2
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Un-define HAVE_REDUND, if you want to use the utilities on a system
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that does not have support for redundant environment enabled.
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If HAVE_REDUND is undefined, DEVICE2_NAME is ignored,
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as is ENV2_SIZE and DEVICE2_ESIZE.
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The DEVICEx_NAME constants define which MTD character devices are to
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be used to access the environment.
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The DEVICEx_OFFSET constants define the environment offset within the
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MTD character device.
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ENVx_SIZE defines the size in bytes taken by the environment, which
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may be less then flash sector size, if the environment takes less
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then 1 sector.
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DEVICEx_ESIZE defines the size of the first sector in the flash
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partition where the environment resides.
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DEVICEx_ENVSECTORS defines the number of sectors that may be used for
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this environment instance. On NAND this is used to limit the range
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within which bad blocks are skipped, on NOR it is not used.
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To prevent losing changes to the environment and to prevent confusing the MTD
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drivers, a lock file at /var/lock/fw_printenv.lock is used to serialize access
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to the environment.
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