April 1, 2003 CONS 9

### NAME

cnbell, cnflush, cngetc, cngetsn, cnhalt, cnpollc, cnputc - console access interface

### SYNOPSIS

```void` cnbell(```u_int pitch``, u_int period``, u_int volume`)
```void` cnflush(```void`)
```int` cngetc(```void`)
```int` cngetsn(```char *cp``, int size`)
```void` cnhalt(```void`)
```void` cnpollc(```int on`)
```void` cnputc(```int c`)

### DESCRIPTION

These functions operate over the current console device. The console must be initialized before these functions can be used.

Console input polling functions cngetc(``), cngetsn(``) and cnpollc(``) are only to be used during initial system boot, e.g., when asking for root and dump device or to get necessary user input within mountroothooks. Once the system boots, user input is read via standard tty(4) facilities.

The following is a brief description of each function:

cnbell(``)
  Ring a bell at appropriate ```pitch`, for duration of ```period` milliseconds at given ```volume`. Note that the ```volume` value is ignored commonly.

cnflush(``)
  Waits for all pending output to finish.

cngetc(``)
  Poll (busy wait) for an input and return the input key. Returns 0 if there is no console input device. cnpollc(``) must be called before cngetc(``) could be used. cngetc(``) should be used during kernel startup only.

cngetsn(``)
  Read one line of user input, stop reading once the newline key is input. Input is echoed back. This uses cnpollc(``) and cngetc(``). Number of read characters is ```size` at maximum, user is notified by console bell when the end of input buffer is reached. <Backspace> key works as expected. <@> or <CTRL>-u make cngetsn(``) discard input read so far, print newline and wait for next input. cngetsn(``) returns number of characters actually read, excluding the final newline. ```cp` is not zero-ended before return. cngetsn(``) should be used during kernel startup only.

cnhalt(``)
  Terminates the console device (i.e. cleanly shuts down the console hardware.)

cnpollc(``)
  Switch the console driver to polling mode if ```on` is nonzero, or back to interrupt driven mode if ```on` is zero. cnpollc(``) should be used during kernel startup only.

cnputc(``)
  Console kernel output character routine. Commonly, kernel code uses printf(9) rather than using this low-level interface.

### EXAMPLES

This waits until a <Enter> key is pressed:

``

    int c;

    cnpollc(1);
    for(;;) {
            c = cngetc();
            if ((c == '\r' || (c == '\n')) {
                    printf("\n");
                    break;
            }
    }
    cnpollc(0);

### SEE ALSO

pckbd(4), pcppi(4), tty(4), wscons(4), wskbd(4), printf(9), spl(9), wscons(9)