TTCOMPAT(4M)

NAME
ttcompat - V7 and 4BSD STREAMS compatibility module

CONFIG
None; included by default.

SYNOPSIS
#include <sys/types.h>
#include <sys/stream.h>
#include <sys/stropts.h>

ioctl(fd, I_PUSH, "ttcompat");

DESCRIPTION

ttcompat is a STREAMS module that translates the ioctl calls supported by the older Version 7 and 4BSD terminal drivers into the ioctl calls supported by the termio(4) interface. All other messages pass through this module unchanged; the behavior of read and write calls is unchanged, as is the behavior of ioctl calls other than the ones supported by ttcompat.

Normally, this module is automatically pushed onto a stream when a terminal device is opened; it does not have to be explicitly pushed onto a stream. This module requires that the termio interface be supported by the modules and driver downstream. The TCGETS, TCSETS, and TCSETSF ioctl calls must be supported; if any information set or fetched by those ioctl calls is not supported by the modules and driver downstream, some of the V7/4BSD functions may not be supported. For example, if the CBAUD bits in the c_cflag field are not supported, the functions provided by the sg_ispeed and sg_ospeed fields of the sgttyb structure (see below) will not be supported. If the TCFLSH ioctl is not supported, the function provided by the TIOCFLUSH ioctl will not be supported. If the TCXONC ioctl is not supported, the functions provided by the TIOCSTOP and TIOCSTART ioctl calls will not be supported. If the TIOCMBIS and TIOCMBIC ioctl calls are not supported, the functions provided by the TIOCSDTR and TIOCCDTR ioctl calls will not be supported.

The basic ioctl calls use the sgttyb structure defined by <sys/ioctl.h>:
    struct sgttyb {
    	char	sg_ispeed;
    	char	sg_ospeed;
    	char	sg_erase;
    	char	sg_kill;
    	short	sg_flags;
    };

The sg_ispeed and sg_ospeed fields describe the input and output speeds of the device, and reflect the values in the c_cflag field of the termio structure. The sg_erase and sg_kill fields of the argument structure specify the erase and kill characters respectively, and reflect the values in the VERASE and VKILL members of the c_cc field of the termio structure.

The sg_flags field of the argument structure contains several flags that determine the system's treatment of the terminal. They are mapped into flags in fields of the terminal state, represented by the termio structure.

Delay type 0 is always mapped into the equivalent delay type 0 in the c_oflag field of the termio structure. Other delay mappings are performed as follows:

    sg_flags
        c_oflag

    BS1 BS1
    FF1 VT1
    CR1 CR2
    CR2 CR3
    CR3 not supported
    TAB1
        TAB1
    TAB2
        TAB2
    XTABS
        TAB3
    NL1 ONLRET|CR1
    NL2 NL1

If previous TIOCLSET or TIOCLBIS ioctl calls have not selected LITOUT or PASS8 mode, and if RAW mode is not selected, the ISTRIP flag is set in the c_iflag field of the termio structure, and the EVENP and ODDP flags control the parity of characters sent to the terminal and accepted from the terminal:

0   Parity is not to be generated on output or checked on input; the character size is set to CS8 and the PARENB flag is cleared in the c_cflag field of the termio structure.

EVENP
    Even parity characters are to be generated on output and accepted on input; the INPCK flag is set in the c_iflag field of the termio structure, the character size is set to CS7 and the PARENB flag is set in the c_cflag field of the termio structure.

ODDP
    Odd parity characters are to be generated on output and accepted on input; the INPCK flag is set in the c_iflag field, the character size is set to CS7 and the PARENB and PARODD flags are set in the c_cflag field of the termio structure.

EVENP|ODDP
    Even parity characters are to be generated on output and characters of either parity are to be accepted on input; the INPCK flag is cleared in the c_iflag field, the character size is set to CS7 and the PARENB flag is set in the c_cflag field of the termio structure.

The RAW flag disables all output processing (the OPOST flag in the c_oflag field, and the XCASE flag in the c_lflag field, are cleared in the termio structure) and input processing (all flags in the c_iflag field other than the IXOFF and IXANY flags are cleared in the termio structure). 8 bits of data, with no parity bit, are accepted on input and generated on output; the character size is set to CS8 and the PARENB and PARODD flags are cleared in the c_cflag field of the termio structure. The signal-generating and line-editing control characters are disabled by clearing the ISIG and ICANON flags in the c_lflag field of the termio structure.

The CRMOD flag turn input RETURN characters into NEWLINE characters, and output and echoed NEWLINE characters to be output as a RETURN followed by a LINEFEED. The ICRNL flag in the c_iflag field, and the OPOST and ONLCR flags in the c_oflag field, are set in the termio structure.

The LCASE flag maps upper-case letters in the ASCII character set to their lower-case equivalents on input (the IUCLC flag is set in the c_iflag field), and maps lower-case letters in the ASCII character set to their upper-case equivalents on output (the OLCUC flag is set in the c_oflag field). Escape sequences are accepted on input, and generated on output, to handle certain ASCII characters not supported by older terminals (the XCASE flag is set in the c_lflag field).

Other flags are directly mapped to flags in the termio structure:

    sg_flags
        flags in termio structure

    CBREAK
        complement of ICANON in c_lflag field
    ECHO
        ECHO in c_lflag field
    TANDEM
        IXOFF in c_iflag field

Another structure associated with each terminal specifies characters that are special in both the old Version 7 and the newer 4BSD terminal interfaces. The following structure is defined by <sys/ioctl.h>:
    struct tchars {
    	char	t_intrc;	/* interrupt */
    	char	t_quitc;	/* quit */
    	char	t_startc;	/* start output */
    	char	t_stopc;	/* stop output */
    	char	t_eofc;		/* end-of-file */
    	char	t_brkc;		/* input delimiter (like nl) */
    };

The characters are mapped to members of the c_cc field of the termio structure as follows:

    tchars
        c_cc index

    t_intrc
        VINTR
    t_quitc
        VQUIT
    t_startc
        VSTART
    t_stopc
        VSTOP
    t_eofc
        VEOF
    t_brkc
        VEOL

Also associated with each terminal is a local flag word, specifying flags supported by the new 4BSD terminal interface. Most of these flags are directly mapped to flags in the termio structure:

    local flags
        flags in termio structure

    LCRTBS
        not supported
    LPRTERA
        ECHOPRT in the c_lflag field
    LCRTERA
        ECHOE in the c_lflag field
    LTILDE
        not supported
    LTOSTOP
        TOSTOP in the c_lflag field
    LFLUSHO
        FLUSHO in the c_lflag field
    LNOHANG
        CLOCAL in the c_cflag field
    LCRTKIL
        ECHOKE in the c_lflag field
    LCTLECH
        CTLECH in the c_lflag field
    LPENDIN
        PENDIN in the c_lflag field
    LDECCTQ
        complement of IXANY in the c_iflag field
    LNOFLSH
        NOFLSH in the c_lflag field

Another structure associated with each terminal is the ltchars structure which defines control characters for the new 4BSD terminal interface. Its structure is:
    struct ltchars {
    	char	t_suspc;	/* stop process signal */
    	char	t_dsuspc;	/* delayed stop process signal */
    	char	t_rprntc;	/* reprint line */
    	char	t_flushc;	/* flush output (toggles) */
    	char	t_werasc;	/* word erase */
    	char	t_lnextc;	/* literal next character */
    };

The characters are mapped to members of the c_cc field of the termio structure as follows:

    ltchars
        c_cc index

    t_suspc
        VSUSP
    t_dsuspc
        VDSUSP
    t_rprntc
        VREPRINT
    t_flushc
        VDISCARD
    t_werasc
        VWERASE
    t_lnextc
        VLNEXT

IOCTLS

ttcompat responds to the following ioctl calls. All others are passed to the module below.

TIOCGETP
    The argument is a pointer to an sgttyb structure. The current terminal state is fetched; the appropriate characters in the terminal state are stored in that structure, as are the input and output speeds. The values of the flags in the sg_flags field are derived from the flags in the terminal state and stored in the structure.

TIOCSETP
    The argument is a pointer to an sgttyb structure. The appropriate characters and input and output speeds in the terminal state are set from the values in that structure, and the flags in the terminal state are set to match the values of the flags in the sg_flags field of that structure. The state is changed with a TCSETSF ioctl, so that the interface delays until output is quiescent, then throws away any unread characters, before changing the modes.

TIOCSETN
    The argument is a pointer to an sgttyb structure. The terminal state is changed as TIOCSETP would change it, but a TCSETS ioctl is used, so that the interface neither delays nor discards input.

TIOCHPCL
    The argument is ignored. The HUPCL flag is set in the c_cflag word of the terminal state.

TIOCFLUSH
    The argument is a pointer to an int variable. If its value is zero, all characters waiting in input or output queues are flushed. Otherwise, the value of the int is treated as the logical OR of the FREAD and FWRITE flags defined by <sys/file.h>; if the FREAD bit is set, all characters waiting in input queues are flushed, and if the FWRITE bit is set, all characters waiting in output queues are flushed.

TIOCSBRK
    The argument is ignored. The break bit is set for the device.

TIOCCBRK
    The argument is ignored. The break bit is cleared for the device.

TIOCSDTR
    The argument is ignored. The Data Terminal Ready bit is set for the device.

TIOCCDTR
    The argument is ignored. The Data Terminal Ready bit is cleared for the device.

TIOCSTOP
    The argument is ignored. Output is stopped as if the STOP character had been typed.

TIOCSTART
    The argument is ignored. Output is restarted as if the START character had been typed.

TIOCGETC
    The argument is a pointer to an tchars structure. The current terminal state is fetched, and the appropriate characters in the terminal state are stored in that structure.

TIOCSETC
    The argument is a pointer to an tchars structure. The values of the appropriate characters in the terminal state are set from the characters in that structure.

TIOCLGET
    The argument is a pointer to an int. The current terminal state is fetched, and the values of the local flags are derived from the flags in the terminal state and stored in the int pointed to by the argument.

TIOCLBIS
    The argument is a pointer to an int whose value is a mask containing flags to be set in the local flags word. The current terminal state is fetched, and the values of the local flags are derived from the flags in the terminal state; the specified flags are set, and the flags in the terminal state are set to match the new value of the local flags word.

TIOCLBIC
    The argument is a pointer to an int whose value is a mask containing flags to be cleared in the local flags word. The current terminal state is fetched, and the values of the local flags are derived from the flags in the terminal state; the specified flags are cleared, and the flags in the terminal state are set to match the new value of the local flags word.

TIOCLSET
    The argument is a pointer to an int containing a new set of local flags. The flags in the terminal state are set to match the new value of the local flags word.

TIOCGLTC
    The argument is a pointer to an ltchars structure. The values of the appropriate characters in the terminal state are stored in that structure.

TIOCSLTC
    The argument is a pointer to an ltchars structure. The values of the appropriate characters in the terminal state are set from the characters in that structure.

SEE ALSO
ioctl(2), termio(4)