logging: log_cmds: init uninitialized backend on log_go()

For backends that do not autostart themselves, initialize
& enable them on `log backend <log_backend_*> go`, so
that they function properly.

Signed-off-by: Yong Cong Sin <ycsin@meta.com>
Signed-off-by: Yong Cong Sin <yongcong.sin@gmail.com>
(cherry picked from commit f840a35)

include/zephyr/logging/log_backend.h

@@ -83,6 +83,7 @@ struct log_backend_control_block {
 	void *ctx;
 	uint8_t id;
 	bool active;
+	bool initialized;
 
 	/* Initialization level. */
 	uint8_t level;
@@ -140,6 +141,7 @@ static inline void log_backend_init(const struct log_backend *const backend)
 	if (backend->api->init) {
 		backend->api->init(backend);
 	}
+	backend->cb->initialized = true;
 }
 
 /**

subsys/logging/log_cmds.c

@@ -341,7 +341,19 @@ static int log_go(const struct shell *sh,
 		  char **argv)
 {
 	if (backend || !IS_ENABLED(CONFIG_LOG_FRONTEND)) {
-		log_backend_activate(backend, backend->cb->ctx);
+		if (!backend->cb->initialized) {
+			log_backend_init(backend);
+			while (log_backend_is_ready(backend) != 0) {
+				if (IS_ENABLED(CONFIG_MULTITHREADING)) {
+					k_msleep(10);
+				}
+			}
+			if (log_backend_is_ready(backend) == 0) {
+				log_backend_enable(backend, backend->cb->ctx, CONFIG_LOG_MAX_LEVEL);
+			}
+		} else {
+			log_backend_activate(backend, backend->cb->ctx);
+		}
 		return 0;
 	}