Kernel: Add some functionality to disable TTY input/output

Userspace programs can call tty_ctrl() to disable/enable tty from
handling input and displaying output.

This API is probably going to change in the future to ioctl calls
but I'm not sure how ioctl is used and what functionality should it
have. I decided to create whole new function and syscall for now.

Next I will expose framebuffer in /dev/fb0 and then I can start work
on graphical environment! :D

libc/include/sys/banan-os.h

@@ -0,0 +1,25 @@
+#ifndef _SYS_BANAN_OS_H
+#define _SYS_BANAN_OS_H 1
+
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#define TTY_CMD_SET		0x01
+#define TTY_CMD_UNSET	0x02
+
+#define TTY_FLAG_ENABLE_OUTPUT	1
+#define TTY_FLAG_ENABLE_INPUT	2
+
+/*
+fildes:		refers to valid tty device
+command:	one of TTY_CMD_* definitions
+flags:		bitwise or of TTY_FLAG_* definitions
+
+return value: 0 on success, -1 on failure and errno set to the error
+*/
+int tty_ctrl(int fildes, int command, int flags);
+
+__END_DECLS
+
+#endif

libc/include/sys/syscall.h

@@ -53,6 +53,7 @@ __BEGIN_DECLS
 #define SYS_SYNC 50
 #define SYS_MMAP 51
 #define SYS_MUNMAP 52
+#define SYS_TTY_CTRL 53
 
 __END_DECLS