HowCanIAccessUBootEnvironmentVariablesInLinux < DULG

%SECTION0{name=HowCanIAccessUBootEnvironmentVariablesInLinux }% How can I access U-Boot environment variables in Linux? 

   Question:: I would like to access U-Boot's environment variables from my Linux application.
      Is this possible?

   Answer:: Yes, you can. The environment variables must be stored in flash memory,
      and your Linux kernel must support flash access through the MTD layer.
      In the U-Boot source tree you can find the environment tools in the directory
      =tools/env=, which can be built with command:

<verbatim>
make env
</verbatim>

      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:

<verbatim>
make MTD_VERSION=old env
</verbatim>

      The resulting binary is called =fw_printenv=, but actually includes support for setting
      environment variables too. To achieve this, the binary behaves according to the
      name it is invoked as, so you will have to create a link called =fw_setenv= to =fw_printenv=.

      These tools work exactly like the U-Boot commands =printenv= resp. =setenv=
      You can either build these tools with a fixed configuration selected at compile time,
      or you can configure the tools using the =/etc/fw_env.config= configuration file
      in your target root filesystem. Here is an example configuration file:

      <verbatim>
# Configuration file for fw_(printenv/setenv) utility.
# Up to two entries are valid, in this case the redundant
# environment sector is assumed present.

#########################################################################
# For TQM8xxL modules:
#########################################################################
# MTD device name       Device offset   Env. size       Flash sector size
/dev/mtd0            0x8000          0x4000          0x4000
/dev/mtd0            0xC000          0x4000          0x4000

#########################################################################
# For NSCU:
#########################################################################
# MTD device name       Device offset   Env. size       Flash sector size
#/dev/mtd1              0x0000          0x8000          0x20000
#/dev/mtd2              0x0000          0x8000          0x20000


#########################################################################
# For LWMON
#########################################################################
# MTD device name       Device offset   Env. size       Flash sector size
#/dev/mtd1               0x0000          0x2000          0x40000
      </verbatim>
14.3.27. Use SCC UART with Hardware Handshake		1. Abstract		14.3.29. The =appWeb= server hangs OR /dev/random hangs
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