[posix] add otSysCliInitUsingDaemon API (#9897)

This is to initialize CLI for daemon instance.

With this API, user can redirect the Vendor server CLI output when
needed, and then reset back using this API when the CLI output should
be restored.

src/posix/platform/daemon.cpp

@@ -285,12 +285,7 @@ void Daemon::SetUp(void)
     }
 
 #if OPENTHREAD_POSIX_CONFIG_DAEMON_CLI_ENABLE
-    otCliInit(
-        gInstance,
-        [](void *aContext, const char *aFormat, va_list aArguments) -> int {
-            return static_cast<Daemon *>(aContext)->OutputFormatV(aFormat, aArguments);
-        },
-        this);
+    otSysCliInitUsingDaemon(gInstance);
 #endif
 
     Mainloop::Manager::Get().Add(*this);

src/posix/platform/daemon.hpp

@@ -45,10 +45,10 @@ public:
     void TearDown(void);
     void Update(otSysMainloopContext &aContext) override;
     void Process(const otSysMainloopContext &aContext) override;
+    int  OutputFormatV(const char *aFormat, va_list aArguments);
 
 private:
     int  OutputFormat(const char *aFormat, ...);
-    int  OutputFormatV(const char *aFormat, va_list aArguments);
     void createListenSocketOrDie(void);
     void InitializeSessionSocket(void);
 

src/posix/platform/include/openthread/openthread-system.h

@@ -254,6 +254,19 @@ void otSysSetInfraNetif(const char *aInfraNetifName, int aIcmp6Socket);
  */
 bool otSysInfraIfIsRunning(void);
 
+/**
+ * Initializes the CLI module using the daemon.
+ *
+ * This function initializes the CLI module, and assigns the daemon to handle
+ * the CLI output. This function can be invoked multiple times. The typical use case
+ * is that, after OTBR/vendor_server's CLI output redirection, it uses this API to
+ * restore the original daemon's CLI output.
+ *
+ * @param[in] aInstance  The OpenThread instance structure.
+ *
+ */
+void otSysCliInitUsingDaemon(otInstance *aInstance);
+
 #ifdef __cplusplus
 } // end of extern "C"
 #endif

src/posix/platform/system.cpp

@@ -40,6 +40,7 @@
 
 #include <openthread-core-config.h>
 #include <openthread/border_router.h>
+#include <openthread/cli.h>
 #include <openthread/heap.h>
 #include <openthread/tasklet.h>
 #include <openthread/platform/alarm-milli.h>
@@ -401,3 +402,15 @@ void otSysMainloopProcess(otInstance *aInstance, const otSysMainloopContext *aMa
 }
 
 bool IsSystemDryRun(void) { return gDryRun; }
+
+#if OPENTHREAD_POSIX_CONFIG_DAEMON_ENABLE && OPENTHREAD_POSIX_CONFIG_DAEMON_CLI_ENABLE
+void otSysCliInitUsingDaemon(otInstance *aInstance)
+{
+    otCliInit(
+        aInstance,
+        [](void *aContext, const char *aFormat, va_list aArguments) -> int {
+            return static_cast<ot::Posix::Daemon *>(aContext)->OutputFormatV(aFormat, aArguments);
+        },
+        &ot::Posix::Daemon::Get());
+}
+#endif