shell print interface implemented

source/firmware/kernel/interface/shell.h

@@ -19,5 +19,6 @@ struct command {
 
 int shell_init(const struct driver *shell_device);
 int shell_add_command(struct command *command);
+int shell_write(const char *buffer, unsigned int len);
 
 #endif /* SOURCE_FIRMWARE_KERNEL_INTERFACE_SHELL_H_ */

source/firmware/kernel/shell.c

@@ -96,3 +96,10 @@ int shell_add_command(struct command *command)
 	list_add(&shell_object.command_list, &command->item);
 	return 1;
 }
+
+int shell_write(const char *buffer, unsigned int len)
+{
+	if((NULL == buffer) || (NULL == shell_object.shell_device))
+		return -1;
+	return drv_write(shell_object.shell_device, buffer, len);
+}