cmd: add a new command "config" to show .config contents

This feature is inspired by /proc/config.gz of Linux.  In Linux,
if CONFIG_IKCONFIG is enabled, the ".config" file contents are
embedded in the kernel image.  If CONFIG_IKCONFIG_PROC is also
enabled, the ".config" contents are exposed to /proc/config.gz.
Users can do "zcat /proc/config.gz" to check which config options
are enabled on the running kernel image.

The idea is almost the same here; if CONFIG_CMD_CONFIG is enabled,
the ".config" contents are compressed and saved in the U-Boot image,
then printed by the new command "config".

The usage is quite simple.  Enable CONFIG_CMD_CONFIG, then run
 > config
from the command line interface.  The ".config" contents will be
printed on the console.

This feature increases the U-Boot image size by about 4KB (this is
mostly due to the gzip-compressed .config file).  By default, it is
enabled only for Sandbox because we do not care about the memory
footprint on it.  Of course, this feature is architecture agnostic,
so you can enable it on any board if the image size increase is
acceptable for you.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/cmd/config.c b/cmd/config.c
new file mode 100644
index 0000000000..0c7f4e06cd
--- /dev/null
+++ b/cmd/config.c
@@ -0,0 +1,44 @@
+/*
+ * Copyright (C) 2017 Masahiro Yamada <yamada.masahiro@socionext.com>
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <common.h>
+#include <command.h>
+#include <malloc.h>
+
+#include "config_data_gz.h"
+#include "config_data_size.h"
+
+static int do_config(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+{
+	char *dst;
+	unsigned long len = data_size;
+	int ret = CMD_RET_SUCCESS;
+
+	dst = malloc(data_size + 1);
+	if (!dst)
+		return CMD_RET_FAILURE;
+
+	ret = gunzip(dst, data_size, (unsigned char *)data_gz, &len);
+	if (ret) {
+		printf("failed to uncompress .config data\n");
+		ret = CMD_RET_FAILURE;
+		goto free;
+	}
+
+	dst[data_size] = 0;
+	puts(dst);
+
+free:
+	free(dst);
+
+	return ret;
+}
+
+U_BOOT_CMD(
+	config, 1, 1, do_config,
+	"print .config",
+	""
+);