[PATCH v5 4/5] env: Allow environment files to use the C preprocessor

Simon Glass
2021-10-02T00:40:27Z

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.

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

Signed-off-by: Simon Glass <sjg@chromium.org>
---

(no changes since v4)

Changes in v4:
- Add documentation in rST format instead of README
- Move use of += to this patch
- Explain that environment variables may not end in +

Changes in v3:
- Define __UBOOT_CONFIG__ when collecting environment files

Changes in v2:
- Add separate patch to enable C preprocessor for environment files
- Enable var+=value form to simplify composing variables in multiple steps

Makefile | 7 ++++++-
doc/usage/environment.rst | 12 ++++++++++++
scripts/env2string.awk | 6 ++++++
3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 5c3ba37398f..289a2188cec 100644
--- a/Makefile
+++ b/Makefile
@@ -1796,7 +1796,12 @@ ENV_FILE := $(if $(wildcard $(ENV_FILE_BOARD)),$(ENV_FILE_BOARD),$(ENV_FILE_COMM
quiet_cmd_gen_envp = ENVP $@
cmd_gen_envp = \
if [ -f "$(ENV_FILE)" ]; then \
- cat $(ENV_FILE) >$@; \
+ $(CPP) -P $(CFLAGS) -x assembler-with-cpp -D__ASSEMBLY__ \
+ -D__UBOOT_CONFIG__ \
+ -I . -I include \
+ -I $(srctree)/include -include include/config.h \
+ -I$(srctree)/arch/$(ARCH)/include \
+ $(ENV_FILE) -o $@; \
else \
echo -n >$@ ; \
fi
diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst
index 4e0770523eb..426d8f65329 100644
--- a/doc/usage/environment.rst
+++ b/doc/usage/environment.rst
@@ -39,12 +39,24 @@ and has an equals sign immediately afterwards. Spaces before the = are not
permitted. It is a good idea to indent your scripts so that only the 'var='
appears at the start of a line.

+To add additional text to a variable you can use var+=value. This text is
+merged into the variable during the make process and made available as a
+single value to U-Boot. To support this, environment variables may not end
+in `+`.
+
+This file can include C-style comments. Blank lines and multi-line
+variables are supported, and you can use normal C preprocessor directives
+and CONFIG defines from your board config also.
+
For example, for snapper9260 you would create a text file called
`board/bluewater/env/snapper9260.env` containing the environment text.

Example::

stdout=serial
+ #ifdef CONFIG_LCD
+ stdout+=,lcd
+ #endif
bootcmd=
/* U-Boot script for booting */

diff --git a/scripts/env2string.awk b/scripts/env2string.awk
index 661defdc350..6de3e3dd87e 100644
--- a/scripts/env2string.awk
+++ b/scripts/env2string.awk
@@ -29,6 +29,12 @@ NF {
}
var = arr[1]
env = arr[2]
+
+ # Deal with +=
+ if (match(var, "(.*)[+]$", var_arr)) {
+ var = var_arr[1]
+ env = vars[var] env
+ }
} else {
# Change newline to \n
env = env "\\n" $0;
--
2.33.0.800.g4c38ced690-goog