[PATCH v7 3/7] env: Allow U-Boot scripts to be placed in a .env file

Simon Glass
2021-10-16T00:34:35Z

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>/env
directory called <board>.env (or common.env if you want the same
environment for all boards).

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>
---

Changes in v7:
- Use 'env' basename instead of 'environment' for intermediate output files
- Show a message indicating the source text file being used
- Give an error if CONFIG_EXTRA_ENV_SETTINGS is also defined
- Use CONFIG_ENV_SOURCE_FILE instead of rules to specify the text-file name
- Make board.env the default name if CONFIG_ENV_SOURCE_FILE is empty
- Rewrite the documentation
- Drop the use of common.env
- Update awk script to output the whole CONFIG string, or just a comment

Changes in v6:
- Combine the two env2string.awk patches into one

Changes in v5:
- Explain how to include the common.env file
- Explain why variables starting with _ , and / are not supported
- Expand the definition of how to declare an environment variable
- Explain what happens to empty variables
- Update maintainer
- Move use of += to this patch
- Explain that environment variables may not end in +

Changes in v4:
- Move this from being part of configuring U-Boot to part of building it
- Don't put the environment in autoconf.mk as it is not needed
- Add documentation in rST format instead of README
- Drop mention of import/export
- Update awk script to ignore blank lines, as generated by clang
- Add documentation in rST format instead of README

Changes in v3:
- Adjust Makefile to generate the .inc and .h files in separate fules
- Add more detail in the README about the format of .env files
- Improve the comment about " in the awk script
- Correctly terminate environment files with \n
- Define __UBOOT_CONFIG__ when collecting environment files

Changes in v2:
- Move .env file from include/configs to board/
- Use awk script to process environment since it is much easier on the brain
- Add information and updated example script to README
- Add dependency rule so that the environment is rebuilt when it changes
- Add separate patch to enable C preprocessor for environment files
- Enable var+=value form to simplify composing variables in multiple steps

MAINTAINERS | 7 ++++
Makefile | 66 ++++++++++++++++++++++++++++++++-
config.mk | 2 +
doc/usage/environment.rst | 77 ++++++++++++++++++++++++++++++++++++++-
env/Kconfig | 18 +++++++++
env/embedded.c | 1 +
include/env_default.h | 11 ++++++
scripts/env2string.awk | 63 ++++++++++++++++++++++++++++++++
8 files changed, 243 insertions(+), 2 deletions(-)
create mode 100644 scripts/env2string.awk

diff --git a/MAINTAINERS b/MAINTAINERS
index 71f468c00a8..36846528368 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -738,6 +738,13 @@ F: test/env/
F: tools/env*
F: tools/mkenvimage.c

+ENVIRONMENT AS TEXT
+M: Simon Glass <sjg@chromium.org>
+R: Wolfgang Denk <wd@denx.de>
+S: Maintained
+F: doc/usage/environment.rst
+F: scripts/env2string.awk
+
FPGA
M: Michal Simek <michal.simek@xilinx.com>
S: Maintained
diff --git a/Makefile b/Makefile
index f911f703443..ba99a644b63 100644
--- a/Makefile
+++ b/Makefile
@@ -513,6 +513,7 @@ version_h := include/generated/version_autogenerated.h
timestamp_h := include/generated/timestamp_autogenerated.h
defaultenv_h := include/generated/defaultenv_autogenerated.h
dt_h := include/generated/dt.h
+env_h := include/generated/environment.h

no-dot-config-targets := clean clobber mrproper distclean \
help %docs check% coccicheck \
@@ -1785,6 +1786,69 @@ quiet_cmd_sym ?= SYM $@
u-boot.sym: u-boot FORCE
$(call if_changed,sym)

+# Environment processing
+# ---------------------------------------------------------------------------
+
+# Directory where we expect the .env file, if it exists
+ENV_DIR := $(srctree)/board/$(BOARDDIR)
+
+# Basename of .env file, stripping quotes
+ENV_SOURCE_FILE := $(CONFIG_ENV_SOURCE_FILE:"%"=%)
+
+# Filename of .env file
+ENV_FILE_CFG := $(ENV_DIR)/$(ENV_SOURCE_FILE).env
+
+# Default filename, if CONFIG_ENV_SOURCE_FILE is empty
+ENV_FILE_BOARD := $(ENV_DIR)/$(CONFIG_SYS_BOARD:"%"=%).env
+
+# Select between the CONFIG_ENV_SOURCE_FILE and the default one
+ENV_FILE := $(if $(ENV_SOURCE_FILE),$(ENV_FILE_CFG),$(wildcard $(ENV_FILE_BOARD)))
+
+# Run the environment text file through the preprocessor, but only if it is
+# non-empty, to save time and possible build errors if something is wonky with
+# the board
+quiet_cmd_gen_envp = ENVP $@
+ cmd_gen_envp = \
+ if [ -s "$(ENV_FILE)" ]; then \
+ $(CPP) -P $(CFLAGS) -x assembler-with-cpp -D__ASSEMBLY__ \
+ -D__UBOOT_CONFIG__ \
+ -I . -I include -I $(srctree)/include \
+ -include linux/kconfig.h -include include/config.h \
+ -I$(srctree)/arch/$(ARCH)/include \
+ $< -o $@; \
+ else \
+ echo -n >$@ ; \
+ fi
+include/generated/env.in: include/generated/env.txt FORCE
+ $(call cmd,gen_envp)
+
+# Regenerate the environment if it changes
+# We use 'wildcard' since the file is not required to exist (at present), in
+# which case we don't want this dependency, but instead should create an empty
+# file
+# This rule is useful since it shows the source file for the environment
+quiet_cmd_envc = ENVC $@
+ cmd_envc = \
+ if [ -f "$<" ]; then \
+ cat $< > $@; \
+ elif [ -n "$(ENV_SOURCE_FILE)" ]; then \
+ echo "Missing file $(ENV_FILE_CFG)"; \
+ else \
+ echo -n >$@ ; \
+ fi
+
+include/generated/env.txt: $(wildcard $(ENV_FILE)) FORCE
+ $(call cmd,envc)
+
+# Write out the resulting environment, converted to a C string
+quiet_cmd_gen_envt = ENVT $@
+ cmd_gen_envt = \
+ awk -f $(srctree)/scripts/env2string.awk $< >>$@
+$(env_h): include/generated/env.in
+ $(call cmd,gen_envt)
+
+# ---------------------------------------------------------------------------
+
# The actual objects are generated when descending,
# make sure no implicit rule kicks in
$(sort $(u-boot-init) $(u-boot-main)): $(u-boot-dirs) ;
@@ -1840,7 +1904,7 @@ endif
# prepare2 creates a makefile if using a separate output directory
prepare2: prepare3 outputmakefile cfg

-prepare1: prepare2 $(version_h) $(timestamp_h) $(dt_h) \
+prepare1: prepare2 $(version_h) $(timestamp_h) $(dt_h) $(env_h) \
include/config/auto.conf
ifeq ($(wildcard $(LDSCRIPT)),)
@echo >&2 " Could not find linker script."
diff --git a/config.mk b/config.mk
index 7bb1fd4ed1b..2595aed218b 100644
--- a/config.mk
+++ b/config.mk
@@ -50,8 +50,10 @@ endif
ifneq ($(BOARD),)
ifdef VENDOR
BOARDDIR = $(VENDOR)/$(BOARD)
+ENVDIR=${vendor}/env
else
BOARDDIR = $(BOARD)
+ENVDIR=${board}/env
endif
endif
ifdef BOARD
diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst
index 7a733b44556..667fd193ea1 100644
--- a/doc/usage/environment.rst
+++ b/doc/usage/environment.rst
@@ -15,7 +15,82 @@ environment is erased by accident, a default environment is provided.

Some configuration options can be set using Environment Variables.

-List of environment variables (most likely not complete):
+Text-based Environment
+----------------------
+
+The default environment for a board is created using a `.env` environment file
+using a simple text format. The base filename for this is defined by
+`CONFIG_ENV_SOURCE_FILE`, or `CONFIG_SYS_BOARD` if that is empty.
+
+The file must be in the board directory and have a .env extension, so
+assuming that there is a board vendor, the resulting filename is therefore::
+
+ board/<vendor>/<board>/<CONFIG_ENV_SOURCE_FILE>.env
+
+or::
+
+ board/<vendor>/<board>/<CONFIG_SYS_BOARD>.env
+
+This is a plain text file where you can type your environment variables in
+the form `var=value`. Blank lines and multi-line variables are supported.
+The conversion script looks for a line that starts in column 1 with a string
+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/snapper9260.env` containing the environment text.
+
+Example::
+
+ stdout=serial
+ #ifdef CONFIG_LCD
+ stdout+=,lcd
+ #endif
+ bootcmd=
+ /* U-Boot script for booting */
+
+ if [ -z ${tftpserverip} ]; then
+ echo "Use 'setenv tftpserverip a.b.c.d' to set IP address."
+ fi
+
+ usb start; setenv autoload n; bootp;
+ tftpboot ${tftpserverip}:
+ bootm
+ failed=
+ /* Print a message when boot fails */
+ echo CONFIG_SYS_BOARD boot failed - please check your image
+ echo Load address is CONFIG_SYS_LOAD_ADDR
+
+If CONFIG_ENV_SOURCE_FILE is empty and the default filename is not present, then
+the old-style C environment is used instead. See below.
+
+Old-style C environment
+-----------------------
+
+Traditionally, the default environment is created in `include/env_default.h`,
+and can be augmented by various `CONFIG` defines. See that file for details. In
+particular you can define `CONFIG_EXTRA_ENV_SETTINGS` in your board file
+to add environment variables.
+
+Board maintainers are encouraged to migrate to the text-based environment as it
+is easier to maintain. The distro-board script still requires the old-style
+environment but work is underway to address this.
+
+
+List of environment variables
+-----------------------------
+
+This is most-likely not complete:

baudrate
see CONFIG_BAUDRATE
diff --git a/env/Kconfig b/env/Kconfig
index f75f2b13536..b93ad5c8ee0 100644
--- a/env/Kconfig
+++ b/env/Kconfig
@@ -3,6 +3,24 @@ menu "Environment"
config ENV_SUPPORT
def_bool y

+config ENV_SOURCE_FILE
+ string "Environment file to use"
+ default ""
+ help
+ This sets the basename to use to generate the default environment.
+ This a text file as described in doc/usage/environment.rst
+
+ The file must be in the board directory and have a .env extension, so
+ the resulting filename is typically
+ board/<vendor>/<board>/<CONFIG_ENV_SOURCE_FILE>.env
+
+ If the file is not present, an error is produced.
+
+ If this CONFIG is empty, U-Boot uses CONFIG SYS_BOARD as a default, if
+ the file board/<vendor>/<board>/<SYS_BOARD>.env exists. Otherwise the
+ environment is assumed to come from the ad-hoc
+ CONFIG_EXTRA_ENV_SETTINGS #define
+
config SAVEENV
def_bool y if CMD_SAVEENV

diff --git a/env/embedded.c b/env/embedded.c
index 208553e6af1..9f26e6cad9c 100644
--- a/env/embedded.c
+++ b/env/embedded.c
@@ -66,6 +66,7 @@
#endif

#define DEFAULT_ENV_INSTANCE_EMBEDDED
+#include <config.h>
#include <env_default.h>

#ifdef CONFIG_ENV_ADDR_REDUND
diff --git a/include/env_default.h b/include/env_default.h
index 66e203eb6e4..c06506313e5 100644
--- a/include/env_default.h
+++ b/include/env_default.h
@@ -10,6 +10,10 @@
#include <env_callback.h>
#include <linux/stringify.h>

+#ifndef USE_HOSTCC
+#include <generated/environment.h>
+#endif
+
#ifdef DEFAULT_ENV_INSTANCE_EMBEDDED
env_t embedded_environment __UBOOT_ENV_SECTION__(environment) = {
ENV_CRC, /* CRC Sum */
@@ -110,6 +114,13 @@ const uchar default_environment[] = {
#if defined(CONFIG_BOOTCOUNT_BOOTLIMIT) && (CONFIG_BOOTCOUNT_BOOTLIMIT > 0)
"bootlimit=" __stringify(CONFIG_BOOTCOUNT_BOOTLIMIT)"\0"
#endif
+#ifdef CONFIG_EXTRA_ENV_TEXT
+# ifdef CONFIG_EXTRA_ENV_SETTINGS
+# error "Your board uses a text-file environment, so must not define CONFIG_EXTRA_ENV_SETTINGS"
+# endif
+ /* This is created in the Makefile */
+ CONFIG_EXTRA_ENV_TEXT
+#endif
#ifdef CONFIG_EXTRA_ENV_SETTINGS
CONFIG_EXTRA_ENV_SETTINGS
#endif
diff --git a/scripts/env2string.awk b/scripts/env2string.awk
new file mode 100644
index 00000000000..9efb8f07b9f
--- /dev/null
+++ b/scripts/env2string.awk
@@ -0,0 +1,63 @@
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Copyright 2021 Google, Inc
+#
+# SPDX-License-Identifier: GPL-2.0+
+#
+# Awk script to parse a text file containing an environment and convert it
+# to a C string which can be compiled into U-Boot.
+
+# The resulting output is:
+#
+# #define CONFIG_EXTRA_ENV_TEXT "<environment here>"
+#
+# If the input is empty, this script outputs a comment instead.
+
+BEGIN {
+ # env holds the env variable we are currently processing
+ env = "";
+ ORS = ""
+}
+
+# Skip empty lines, as these are generated by the clang preprocessor
+NF {
+ # Quote quotes
+ gsub("\"", "\\\"")
+
+ # Is this the start of a new environment variable?
+ if (match($0, "^([^ =][^ =]*)=(.*)", arr)) {
+ if (length(env) != 0) {
+ # Record the value of the variable now completed
+ vars[var] = env
+ }
+ var = arr[1]
+ env = arr[2]
+
+ # Deal with +=
+ if (match(var, "(.*)[+]$", var_arr)) {
+ var = var_arr[1]
+ env = vars[var] env
+ }
+ } else {
+ # Change newline to \n
+ env = env "\\n" $0;
+ }
+}
+
+END {
+ # Record the value of the variable now completed. If the variable is
+ # empty it is not set.
+ if (length(env) != 0) {
+ vars[var] = env
+ }
+
+ if (length(vars) != 0) {
+ printf("%s", "#define CONFIG_EXTRA_ENV_TEXT \"")
+
+ # Print out all the variables
+ for (var in vars) {
+ print var "=" vars[var] "\\0"
+ }
+ print "\"\n"
+ }
+}
--
2.33.0.1079.g6e70778dc9-goog