[U-Boot] [PATCH v4 07/13] Add standard environment variables README

[Jason Hobbs]

Signed-off-by: Jason Hobbs <jason.hobbs at calxeda.com>
---
new in v4

 doc/README.standard-env |   92 +++++++++++++++++++++++++++++++++++++++++++++++
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 create mode 100644 doc/README.standard-env

diff --git a/doc/README.standard-env b/doc/README.standard-env
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+/*
+ * Copyright 2011, Calxeda Inc.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+**********************************
+* Standard Environment Variables *
+**********************************
+
+The use of environment variables to hold addresses, file names, and
+other values used during booting is a common practice across U-boot
+platforms. Many platforms have variables that are used for the same
+common tasks, such as pointing to a kernel in memory, or naming a
+ramdisk file. Since these environment variables typically originate in
+board config files rather than common code, it's easy (and has been
+common) for different boards to use different environment variable
+names for the exact same purpose.
+
+Here, we provide a of standard environment variable names that should be
+used for any board that uses an environment variable that provides one
+of the values listed here. That doesn't mean each board must provide all
+of these variables - only that if it needs to describe one of the items
+listed here, it should use the standard variable for that. Failure to
+use the standard variable can result in loss of functionality when common
+code is used that expects variable names to follow the standard.
+
+WARNING: Unfortunately, it's not yet safe to assume that a variable with
+a name matching one of those below is used for the purpose listed in
+this README. There are currently board configs with variable names
+matching those listed below in name, but not purpose.
+
+TFTP Filenames
+==============
+Each of these variables contains the name of a file on a TFTP server.
+
+Variable			Contains
+--------			--------
+u-boot				U-boot binary image
+bootfile			Linux kernel image
+fdtfile				device tree blob
+ramdiskfile			ramdisk image
+
+Load Addresses
+==============
+Each of these variables contains an address in RAM at which the object
+is (or can be) loaded.
+
+Variable			Contains
+--------			--------
+u-boot_addr_r			U-boot binary image
+kernel_addr_r			Linux kernel image
+fdt_addr_r			device tree blob
+ramdisk_addr_r			ramdisk image
+
+Flash locations
+===============
+Each of these variables contains an address in NOR flash, or an offset in
+NAND flash, at which the object is stored.
+
+Variable			Contains
+--------			--------
+u-boot_addr			U-boot binary image
+kernel_addr			Linux kernel image
+fdt_addr			device tree blob
+ramdisk_addr			ramdisk image
+
+Other
+=====
+Miscellaneous
+
+Variable			Contains
+--------			--------
+bootargs			Command line arguments for the kernel
+loadaddr			Address in RAM to load a file to, from various
+				sources.
+serverip			The IP address of the TFTP server to use when
+				retrieving files.
+
-- 
1.7.0.4