cngetc(9) - NetBSD Manual Pages

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CONS(9)                NetBSD Kernel Developer's Manual                CONS(9)


NAME

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


SYNOPSIS

     #include <dev/cons.h>

     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 mil-
                liseconds 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 inter-
                face.


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)

NetBSD 10.99                     June 8, 2010                     NetBSD 10.99