Add qemu 2.4.0

[kvmfornfv.git] / qemu / roms / u-boot / tools / env / README

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+
+This is a demo implementation of a Linux command line tool to access
+the U-Boot's environment variables.
+
+In order to cross-compile fw_printenv, run
+    make CROSS_COMPILE=<your cross-compiler prefix> env
+in the root directory of the U-Boot distribution. For example,
+    make CROSS_COMPILE=arm-linux- env
+
+For the run-time utility 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 DEVICE1_ENVSECTORS     2
+#define DEVICE2_OFFSET    0x0000
+#define ENV2_SIZE         0x4000
+#define DEVICE2_ESIZE     0x4000
+#define DEVICE2_ENVSECTORS     2
+
+Un-define HAVE_REDUND, if you want to use the utilities 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.
+
+DEVICEx_ENVSECTORS defines the number of sectors that may be used for
+this environment instance. On NAND this is used to limit the range
+within which bad blocks are skipped, on NOR it is not used.
+
+To prevent losing changes to the environment and to prevent confusing the MTD
+drivers, a lock file at /var/lock/fw_printenv.lock is used to serialize access
+to the environment.