[U-Boot] [PATCH v1] common: command: Add command execution tracer.

[Christoph Muellner]

When using boot scripts it can become quite hard to understand
which commands are actually executed during bootup (e.g. where
is a kernel image loaded from or which DTB is in use).

Shell scripts suffer from a similar problem and many shells address
this problem with a command execution tracer (e.g. BASH has xtrace,
which can be enabled by "set -x").

This patch introduces a command tracer for U-Boot, which prints
every command with its arguments before it is executed.

Signed-off-by: Christoph Muellner <christoph.muellner at theobroma-systems.com>

---

 cmd/Kconfig      | 11 +++++++++++
 common/command.c | 14 ++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/cmd/Kconfig b/cmd/Kconfig
index 0b07b3b9d77..eeadc3827cb 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -53,6 +53,17 @@ config SYS_PROMPT
 	  This string is displayed in the command line to the left of the
 	  cursor.
 
+config SYS_XTRACE
+	string "Command execution tracer"
+	depends on CMDLINE
+	default y if CMDLINE
+	help
+	  This option enables the possiblity to print all commands before
+	  executing them and after all variables are evaluated (similar
+	  to Bash's xtrace/'set -x' feature).
+	  To enable the tracer a variable "xtrace" needs to be defined in
+	  the environment.
+
 menu "Autoboot options"
 
 config AUTOBOOT
diff --git a/common/command.c b/common/command.c
index e14d1fa1d6b..e192bb2a619 100644
--- a/common/command.c
+++ b/common/command.c
@@ -574,6 +574,20 @@ enum command_ret_t cmd_process(int flag, int argc, char * const argv[],
 	enum command_ret_t rc = CMD_RET_SUCCESS;
 	cmd_tbl_t *cmdtp;
 
+#if defined(CONFIG_SYS_XTRACE)
+	char *xtrace;
+
+	xtrace = env_get("xtrace");
+	if (xtrace) {
+		puts("+");
+		for (int i = 0; i < argc; i++) {
+			puts(" ");
+			puts(argv[i]);
+		}
+		puts("\n");
+	}
+#endif
+
 	/* Look up command in command table */
 	cmdtp = find_cmd(argv[0]);
 	if (cmdtp == NULL) {
-- 
2.11.0