[PATCH v3 2/2] cli: flush stdin before enabling cli

[Gregor Herburger]

Currently there is no possibility to flush stdin after autocommands are
executed. If in the bootcmd the stdin is changed, e.g. from nulldev to
serial, it could happen that junk characters sit in the fifo and appear
on the cli.

Add a option to clear stdin before starting the CLI.

Signed-off-by: Gregor Herburger <gregor.herburger at linutronix.de>

---

Changes in v3:
- Update helptext

Changes in v2:
- add a common console_flush_stdin to console.c
- replace all caller of while(getchar()) with function call

 cmd/Kconfig  | 8 ++++++++
 common/cli.c | 4 ++++
 2 files changed, 12 insertions(+)

diff --git a/cmd/Kconfig b/cmd/Kconfig
index 322ebe600c5..214b050e511 100644
--- a/cmd/Kconfig
+++ b/cmd/Kconfig
@@ -47,6 +47,14 @@ config HUSH_SELECTABLE
 	default y if HUSH_OLD_PARSER && HUSH_MODERN_PARSER
 endmenu
 
+config CMDLINE_FLUSH_STDIN
+	bool "Enable flushing input before starting cli"
+	help
+	  When this option is enabled the stdin buffer will be flushed before
+	  starting the CLI. This is useful when stdin is changed during boot
+	  (e.g. from nulldev to serial) and junk characters may be pending
+	  in the buffer.
+
 config CMDLINE_EDITING
 	bool "Enable command line editing"
 	default y
diff --git a/common/cli.c b/common/cli.c
index 4694a35cd0e..bcc7264d51a 100644
--- a/common/cli.c
+++ b/common/cli.c
@@ -295,6 +295,10 @@ err:
 void cli_loop(void)
 {
 	bootstage_mark(BOOTSTAGE_ID_ENTER_CLI_LOOP);
+
+	if (IS_ENABLED(CONFIG_CMDLINE_FLUSH_STDIN))
+		console_flush_stdin();
+
 #if CONFIG_IS_ENABLED(HUSH_PARSER)
 	if (gd->flags & GD_FLG_HUSH_MODERN_PARSER)
 		parse_and_run_file();
-- 
2.47.3

base-commit: c704af3c8b0f37929bce8c2a4bba27d6e89919c7
branch: cmd-flush-stdin