|
CONS(9) |
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 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);