shell: Support output using a va_list

At present it is not possible to write a printf()-like function in
board code which outputs to the shell. Add shell_vfprintf() to permit
this.

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

include/shell/shell.h

@@ -726,6 +726,21 @@ int shell_stop(const struct shell *shell);
 void shell_fprintf(const struct shell *shell, enum shell_vt100_color color,
 		   const char *fmt, ...);
 
+/**
+ * @brief vprintf-like function which sends formatted data stream to the shell.
+ *
+ * This function can be used from the command handler or from threads, but not
+ * from an interrupt context. It is similar to shell_fprintf() but takes a
+ * va_list instead of variable arguments.
+ *
+ * @param[in] shell	Pointer to the shell instance.
+ * @param[in] color	Printed text color.
+ * @param[in] fmt	Format string.
+ * @param[in] args	List of parameters to print.
+ */
+void shell_vfprintf(const struct shell *shell, enum shell_vt100_color color,
+		   const char *fmt, va_list args);
+
 /**
  * @brief Print data in hexadecimal format.
  *

subsys/shell/shell.c

@@ -1304,8 +1304,8 @@ void shell_process(const struct shell *shell)
 /* This function mustn't be used from shell context to avoid deadlock.
  * However it can be used in shell command handlers.
  */
-void shell_fprintf(const struct shell *shell, enum shell_vt100_color color,
-		   const char *fmt, ...)
+void shell_vfprintf(const struct shell *shell, enum shell_vt100_color color,
+		   const char *fmt, va_list args)
 {
 	__ASSERT_NO_MSG(shell);
 	__ASSERT(!k_is_in_isr(), "Thread context required.");
@@ -1315,17 +1315,11 @@ void shell_fprintf(const struct shell *shell, enum shell_vt100_color color,
 	__ASSERT_NO_MSG(shell->fprintf_ctx);
 	__ASSERT_NO_MSG(fmt);
 
-	va_list args;
-
 	k_mutex_lock(&shell->ctx->wr_mtx, K_FOREVER);
 	if (!flag_cmd_ctx_get(shell)) {
 		shell_cmd_line_erase(shell);
 	}
-
-	va_start(args, fmt);
 	shell_internal_vfprintf(shell, color, fmt, args);
-	va_end(args);
-
 	if (!flag_cmd_ctx_get(shell)) {
 		shell_print_prompt_and_cmd(shell);
 	}
@@ -1333,6 +1327,19 @@ void shell_fprintf(const struct shell *shell, enum shell_vt100_color color,
 	k_mutex_unlock(&shell->ctx->wr_mtx);
 }
 
+/* This function mustn't be used from shell context to avoid deadlock.
+ * However it can be used in shell command handlers.
+ */
+void shell_fprintf(const struct shell *shell, enum shell_vt100_color color,
+		   const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	shell_vfprintf(shell, color, fmt, args);
+	va_end(args);
+}
+
 static void shell_hexdump_line(const struct shell *shell, unsigned int offset,
 			       const u8_t *data, size_t len)
 {

tests/shell/src/main.c

@@ -316,6 +316,33 @@ static void test_set_root_cmd(void)
 	test_shell_execute_cmd("shell colors on", 0);
 }
 
+static void test_shell_fprintf(void)
+{
+	static const char expect[] = "testing 1 2 3";
+	const struct shell *shell;
+	const char *buf;
+	size_t size;
+
+	shell = shell_backend_dummy_get_ptr();
+	zassert_not_null(shell, "Failed to get shell");
+
+	/* Clear the output buffer */
+	shell_backend_dummy_get_output(shell, &size);
+
+	shell_fprintf(shell, SHELL_VT100_COLOR_DEFAULT, "testing %d %s %c",
+		      1, "2", '3');
+	buf = shell_backend_dummy_get_output(shell, &size);
+	zassert_true(size >= sizeof(expect), "Expected size > %u, got %d",
+		     sizeof(expect), size);
+
+	/*
+	 * There are prompts and various ANSI characters in the output, so just
+	 * check that the string is in there somewhere.
+	 */
+	zassert_true(strstr(buf, expect),
+		     "Expected string to contain '%s', got '%s'", expect, buf);
+}
+
 void test_main(void)
 {
 	ztest_test_suite(shell_test_suite,
@@ -328,7 +355,8 @@ void test_main(void)
 			ztest_unit_test(test_cmd_resize),
 			ztest_unit_test(test_shell_module),
 			ztest_unit_test(test_shell_wildcards_static),
-			ztest_unit_test(test_shell_wildcards_dynamic));
+			ztest_unit_test(test_shell_wildcards_dynamic),
+			ztest_unit_test(test_shell_fprintf));
 
 	ztest_run_test_suite(shell_test_suite);
 }