TTY Line Discipline

Kernel TTY: line discipline, canonical/raw input, termios, and ioctl. More...

Classes
struct	minios_termios
struct	minios_winsize

Macros
#define	TTY_LFLAG_ISIG   0x0001u
#define	TTY_LFLAG_ICANON   0x0002u
#define	TTY_LFLAG_ECHO   0x0008u
#define	VINTR   0
#define	VEOF   1
#define	TTY_NCCS   8
#define	TCGETS   0x5401UL
#define	TCSETS   0x5402UL
#define	TCSETSW   0x5403UL
#define	TCSETSF   0x5404UL
#define	TIOCSCTTY   0x540EUL
#define	TIOCGPGRP   0x540FUL /* get foreground process group id */
#define	TIOCSPGRP   0x5410UL /* set foreground process group id */
#define	TIOCGWINSZ   0x5413UL
#define	TIOCNOTTY   0x5422UL

Functions
void	tty_init (void)
	Sets up the canonical input ring buffer, initialises the default termios (c_lflag = ICANON|ECHO|ISIG, VINTR=^C, VEOF=^D), and sets the window size to SCREEN_ROWS x SCREEN_COLS. Must be called once during kernel boot before tty_keyboard_input() or tty_read() are used.
void	tty_keyboard_input (char c)
	In canonical mode (ICANON set): appends to the line buffer; on newline or VEOF flushes the complete line to the read buffer. In raw mode: writes directly to the read buffer. Echoes to vt_write_byte() if ECHO is set. Sends SIGINT to the foreground process group if ISIG is set and == VINTR. Called from the keyboard interrupt handler (IRQ1).
void	tty_inject_escape (const char *seq, int len)
int	tty_has_data (void)
int	tty_read (void *buf, uint32_t len, int nonblock)
	In canonical mode: blocks (or returns -EAGAIN if nonblock) until a complete line is available, then copies up to @len bytes. In raw mode: returns as many bytes as are immediately available up to @len.
int	tty_write (const void *buf, uint32_t len)
	Forwards each byte to vt_write_byte(), which handles ANSI/VT escape sequence parsing and VGA cell rendering.
int	tty_ioctl (uint64_t cmd, uint64_t arg)
	TCGETS: copies current termios to *arg. TCSETS/TCSETSW: copies termios from *arg into the kernel TTY state. TIOCGWINSZ: copies the window size (SCREEN_ROWS x SCREEN_COLS) to *arg. TIOCSCTTY/TIOCNOTTY: accepted (no-op in single-TTY kernel).
int	tty_isatty_fd (int fd)
	Returns 1 if the fd's vfs_file entry has ftype == VFS_FILE_TYPE_CHAR and device_type == VFS_DEVICE_TTY, 0 otherwise. Used by the isatty(3) Newlib stub.

Detailed Description

Kernel TTY: line discipline, canonical/raw input, termios, and ioctl.

The TTY layer sits between the keyboard driver and userspace. It implements a POSIX-like line discipline: canonical buffering with echo, SIGINT on ^C (ISIG), and raw mode (ICANON cleared). Exposes the /dev/tty device via tty_read()/tty_write() and processes TCGETS/TCSETS/TIOCGWINSZ via tty_ioctl().

Macro Definition Documentation

TCGETS

#define TCGETS   0x5401UL

TCSETS

#define TCSETS   0x5402UL

TCSETSF

#define TCSETSF   0x5404UL

TCSETSW

#define TCSETSW   0x5403UL

TIOCGPGRP

#define TIOCGPGRP   0x540FUL /* get foreground process group id */

TIOCGWINSZ

#define TIOCGWINSZ   0x5413UL

TIOCNOTTY

#define TIOCNOTTY   0x5422UL

TIOCSCTTY

#define TIOCSCTTY   0x540EUL

TIOCSPGRP

#define TIOCSPGRP   0x5410UL /* set foreground process group id */

TTY_LFLAG_ECHO

#define TTY_LFLAG_ECHO   0x0008u

TTY_LFLAG_ICANON

#define TTY_LFLAG_ICANON   0x0002u

TTY_LFLAG_ISIG

#define TTY_LFLAG_ISIG   0x0001u

TTY_NCCS

#define TTY_NCCS   8

VEOF

#define VEOF   1

VINTR

#define VINTR   0

Function Documentation

tty_has_data()

int tty_has_data

(

void

)

tty_has_data() - Return non-zero if the TTY input ring buffer has unread bytes. Used by poll() to report POLLIN readiness for stdin.

Here is the call graph for this function:

Here is the caller graph for this function:

tty_init()

void tty_init

(

void

)

Sets up the canonical input ring buffer, initialises the default termios (c_lflag = ICANON|ECHO|ISIG, VINTR=^C, VEOF=^D), and sets the window size to SCREEN_ROWS x SCREEN_COLS. Must be called once during kernel boot before tty_keyboard_input() or tty_read() are used.

tty_init() - Initialise the TTY subsystem.

Here is the call graph for this function:

Here is the caller graph for this function:

tty_inject_escape()

void tty_inject_escape	(	const char *	seq,
		int	len )

tty_inject_escape() - Inject a multi-byte escape sequence directly into the TTY read buffer, bypassing echo and canonical buffering. @seq: Byte sequence to inject (e.g. "\x1b[A" for cursor-up). @len: Number of bytes to push.

Use for special keys (arrow keys, function keys) whose escape sequences must never be echoed to the screen and must bypass ICANON line buffering.

Here is the call graph for this function:

Here is the caller graph for this function:

tty_ioctl()

int tty_ioctl	(	uint64_t	cmd,
		uint64_t	arg )

TCGETS: copies current termios to *arg. TCSETS/TCSETSW: copies termios from *arg into the kernel TTY state. TIOCGWINSZ: copies the window size (SCREEN_ROWS x SCREEN_COLS) to *arg. TIOCSCTTY/TIOCNOTTY: accepted (no-op in single-TTY kernel).

tty_ioctl() - Handle terminal ioctl commands.

Parameters

cmd	Ioctl command code (TCGETS=0x5401, TCSETS=0x5402, TCSETSW=0x5403, TIOCSCTTY=0x540E, TIOCGWINSZ=0x5413, TIOCNOTTY=0x5422).
arg	User-space pointer to a struct minios_termios or struct minios_winsize, depending on @cmd.

Returns

0 on success, -EINVAL for unknown @cmd.

Here is the call graph for this function:

Here is the caller graph for this function:

tty_isatty_fd()

int tty_isatty_fd

(

int

fd

)

Returns 1 if the fd's vfs_file entry has ftype == VFS_FILE_TYPE_CHAR and device_type == VFS_DEVICE_TTY, 0 otherwise. Used by the isatty(3) Newlib stub.

tty_isatty_fd() - Test whether a file descriptor refers to the TTY device.

Parameters

fd	File descriptor to test.

Returns

1 if @fd is the TTY, 0 if not.

tty_keyboard_input()

void tty_keyboard_input

(

char

c

)

In canonical mode (ICANON set): appends to the line buffer; on newline or VEOF flushes the complete line to the read buffer. In raw mode: writes directly to the read buffer. Echoes to vt_write_byte() if ECHO is set. Sends SIGINT to the foreground process group if ISIG is set and == VINTR. Called from the keyboard interrupt handler (IRQ1).

tty_keyboard_input() - Feed a raw character from the keyboard ISR into the TTY.

Parameters

c	Raw character byte from the PS/2 keyboard driver.

Here is the call graph for this function:

Here is the caller graph for this function:

tty_read()

int tty_read	(	void *	buf,
		uint32_t	len,
		int	nonblock )

In canonical mode: blocks (or returns -EAGAIN if nonblock) until a complete line is available, then copies up to @len bytes. In raw mode: returns as many bytes as are immediately available up to @len.

tty_read() - Read bytes from the TTY input buffer.

Parameters

buf	Destination buffer.
len	Maximum number of bytes to read.
nonblock	Non-zero to return immediately if no data is available (O_NONBLOCK).

Returns

Number of bytes read, 0 on EOF (VEOF character), or -1 on error.

Here is the call graph for this function:

Here is the caller graph for this function:

tty_write()

int tty_write	(	const void *	buf,
		uint32_t	len )

Forwards each byte to vt_write_byte(), which handles ANSI/VT escape sequence parsing and VGA cell rendering.

tty_write() - Write bytes to the TTY output (VGA terminal).

Parameters

buf	Source buffer of bytes to write.
len	Number of bytes.

Returns

Number of bytes written (@len on success, -1 on error).

Here is the call graph for this function:

Here is the caller graph for this function: