env: Allow U-Boot scripts to be placed in a .env file

At present U-Boot environment variables, and thus scripts, are defined
by CONFIG_EXTRA_ENV_SETTINGS. It is painful to add large amounts of text
to this file and dealing with quoting and newlines is harder than it
should be. It would be better if we could just type the script into a
text file and have it included by U-Boot.

Add a feature that brings in a .env file associated with the board
config, if present. To use it, create a file in a board/<vendor>
directory, typically called <board>.env and controlled by the
CONFIG_ENV_SOURCE_FILE option.

The environment variables should be of the form "var=value". Values can
extend to multiple lines. See the README under 'Environment Variables:'
for more information and an example.

In many cases environment variables need access to the U-Boot CONFIG
variables to select different options. Enable this so that the environment
scripts can be as useful as the ones currently in the board config files.
This uses the C preprocessor, means that comments can be included in the
environment using /* ... */

Also support += to allow variables to be appended to. This is needed when
using the preprocessor.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Marek Behún <marek.behun@nic.cz>
Tested-by: Marek Behún <marek.behun@nic.cz>

test/py/tests/test_env.py

@@ -7,6 +7,7 @@
 import os
 import os.path
 from subprocess import call, check_call, CalledProcessError
+import tempfile
 
 import pytest
 import u_boot_utils
@@ -515,3 +516,109 @@ def test_env_ext4(state_test_env):
     finally:
         if fs_img:
             call('rm -f %s' % fs_img, shell=True)
+
+def test_env_text(u_boot_console):
+    """Test the script that converts the environment to a text file"""
+
+    def check_script(intext, expect_val):
+        """Check a test case
+
+        Args:
+            intext: Text to pass to the script
+            expect_val: Expected value of the CONFIG_EXTRA_ENV_TEXT string, or
+                None if we expect it not to be defined
+        """
+        with tempfile.TemporaryDirectory() as path:
+            fname = os.path.join(path, 'infile')
+            with open(fname, 'w') as inf:
+                print(intext, file=inf)
+            result = u_boot_utils.run_and_log(cons, ['awk', '-f', script, fname])
+            if expect_val is not None:
+                expect = '#define CONFIG_EXTRA_ENV_TEXT "%s"\n' % expect_val
+                assert result == expect
+            else:
+                assert result == ''
+
+    cons = u_boot_console
+    script = os.path.join(cons.config.source_dir, 'scripts', 'env2string.awk')
+
+    # simple script with a single var
+    check_script('fred=123', 'fred=123\\0')
+
+    # no vars
+    check_script('', None)
+
+    # two vars
+    check_script('''fred=123
+ernie=456''', 'fred=123\\0ernie=456\\0')
+
+    # blank lines
+    check_script('''fred=123
+
+
+ernie=456
+
+''', 'fred=123\\0ernie=456\\0')
+
+    # append
+    check_script('''fred=123
+ernie=456
+fred+= 456''', 'fred=123 456\\0ernie=456\\0')
+
+    # append from empty
+    check_script('''fred=
+ernie=456
+fred+= 456''', 'fred= 456\\0ernie=456\\0')
+
+    # variable with + in it
+    check_script('fred+ernie=123', 'fred+ernie=123\\0')
+
+    # ignores variables that are empty
+    check_script('''fred=
+fred+=
+ernie=456''', 'ernie=456\\0')
+
+    # single-character env name
+    check_script('''f=123
+e=456
+f+= 456''', 'e=456\\0f=123 456\\0')
+
+    # contains quotes
+    check_script('''fred="my var"
+ernie=another"''', 'fred=\\"my var\\"\\0ernie=another\\"\\0')
+
+    # variable name ending in +
+    check_script('''fred\\+=my var
+fred++= again''', 'fred+=my var again\\0')
+
+    # variable name containing +
+    check_script('''fred+jane=both
+fred+jane+=again
+ernie=456''', 'fred+jane=bothagain\\0ernie=456\\0')
+
+    # multi-line vars - new vars always start at column 1
+    check_script('''fred=first
+ second
+\tthird with tab
+
+   after blank
+ confusing=oops
+ernie=another"''', 'fred=first second third with tab after blank confusing=oops\\0ernie=another\\"\\0')
+
+    # real-world example
+    check_script('''ubifs_boot=
+	env exists bootubipart ||
+		env set bootubipart UBI;
+	env exists bootubivol ||
+		env set bootubivol boot;
+	if ubi part ${bootubipart} &&
+		ubifsmount ubi${devnum}:${bootubivol};
+	then
+		devtype=ubi;
+		run scan_dev_for_boot;
+	fi
+''',
+        'ubifs_boot=env exists bootubipart || env set bootubipart UBI; '
+        'env exists bootubivol || env set bootubivol boot; '
+        'if ubi part ${bootubipart} && ubifsmount ubi${devnum}:${bootubivol}; '
+        'then devtype=ubi; run scan_dev_for_boot; fi\\0')