shell: Fix shell init procedure when configured as inactive on startup

The previous behavior of the CONFIG_SHELL_AUTOSTART option, where setting
it to 'n' disabled shell interaction at startup but kept the logger
active as a shell backend, was inconsistent.
Now, when CONFIG_SHELL_AUTOSTART is set to 'n', both the shell and the
logger are inactive at startup. Calling the shell_start function will
activate them and print any pending logs. This change ensures a more
consistent and logical behavior regarding shell and logger activity at
startup.

Additionally, now when the shell_stop function is called, both the shell
and the logger are halted. This enhancement ensures that stopping
the shell also effectively stops the associated logger.

Signed-off-by: Jakub Rzeszutko <jakub.rzeszutko@verkada.com>

include/zephyr/shell/shell.h

@@ -743,6 +743,7 @@ struct shell_backend_ctx_flags {
 	uint32_t cmd_ctx      :1; /*!< Shell is executing command */
 	uint32_t print_noinit :1; /*!< Print request from not initialized shell */
 	uint32_t sync_mode    :1; /*!< Shell in synchronous mode */
+	uint32_t handle_log   :1; /*!< Shell is handling logger backend */
 };
 
 BUILD_ASSERT((sizeof(struct shell_backend_ctx_flags) == sizeof(uint32_t)),
@@ -798,6 +799,9 @@ struct shell_ctx {
 	/** When bypass is set, all incoming data is passed to the callback. */
 	shell_bypass_cb_t bypass;
 
+	/*!< Logging level for a backend. */
+	uint32_t log_level;
+
 #if defined CONFIG_SHELL_GETOPT
 	/*!< getopt context for a shell backend. */
 	struct getopt_state getopt;

subsys/shell/shell.c

@@ -1315,21 +1315,16 @@ void shell_thread(void *shell_handle, void *arg_log_backend,
 		  void *arg_log_level)
 {
 	struct shell *sh = shell_handle;
-	bool log_backend = (bool)arg_log_backend;
-	uint32_t log_level = POINTER_TO_UINT(arg_log_level);
 	int err;
 
+	z_flag_handle_log_set(sh, (bool)arg_log_backend);
+	sh->ctx->log_level = POINTER_TO_UINT(arg_log_level);
+
 	err = sh->iface->api->enable(sh->iface, false);
 	if (err != 0) {
 		return;
 	}
 
-	if (IS_ENABLED(CONFIG_SHELL_LOG_BACKEND) && log_backend
-	    && !IS_ENABLED(CONFIG_SHELL_START_OBSCURED)) {
-		z_shell_log_backend_enable(sh->log_backend, (void *)sh,
-					   log_level);
-	}
-
 	if (IS_ENABLED(CONFIG_SHELL_AUTOSTART)) {
 		/* Enable shell and print prompt. */
 		err = shell_start(sh);
@@ -1430,6 +1425,11 @@ int shell_start(const struct shell *sh)
 		return -ENOTSUP;
 	}
 
+	if (IS_ENABLED(CONFIG_SHELL_LOG_BACKEND) && z_flag_handle_log_get(sh)
+	    && !z_flag_obscure_get(sh)) {
+		z_shell_log_backend_enable(sh->log_backend, (void *)sh, sh->ctx->log_level);
+	}
+
 	k_mutex_lock(&sh->ctx->wr_mtx, K_FOREVER);
 
 	if (IS_ENABLED(CONFIG_SHELL_VT100_COLORS)) {
@@ -1460,6 +1460,8 @@ int shell_stop(const struct shell *sh)
 
 	state_set(sh, SHELL_STATE_INITIALIZED);
 
+	z_shell_log_backend_disable(sh->log_backend);
+
 	return 0;
 }
 

subsys/shell/shell_ops.h

@@ -221,6 +221,19 @@ static inline bool z_flag_sync_mode_set(const struct shell *sh, bool val)
 	return ret;
 }
 
+static inline bool z_flag_handle_log_get(const struct shell *sh)
+{
+	return sh->ctx->ctx.flags.handle_log == 1;
+}
+
+static inline bool z_flag_handle_log_set(const struct shell *sh, bool val)
+{
+	bool ret;
+
+	Z_SHELL_SET_FLAG_ATOMIC(sh, ctx, handle_log, val, ret);
+	return ret;
+}
+
 /* Function sends VT100 command to clear the screen from cursor position to
  * end of the screen.
  */