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.Dd June 8, 2010
.Dt CONS 9
.Os
.Sh NAME
.Nm cnbell ,
.Nm cnflush ,
.Nm cngetc ,
.Nm cngetsn ,
.Nm cnhalt ,
.Nm cnpollc ,
.Nm cnputc
.Nd console access interface
.Sh SYNOPSIS
.In dev/cons.h
.Ft void
.Fn cnbell "u_int pitch" "u_int period" "u_int volume"
.Ft void
.Fn cnflush "void"
.Ft int
.Fn cngetc "void"
.Ft int
.Fn cngetsn "char *cp" "int size"
.Ft void
.Fn cnhalt "void"
.Ft void
.Fn cnpollc "int on"
.Ft void
.Fn cnputc "int c"
.Sh DESCRIPTION
These functions operate over the current console device.
The console must be initialized before these functions can be used.
.Pp
Console input polling functions
.Fn cngetc ,
.Fn cngetsn
and
.Fn 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
.Xr tty 4
facilities.
.Pp
The following is a brief description of each function:
.Bl -tag -width "cngetsn()"
.It Fn cnbell
Ring a bell at appropriate
.Fa pitch ,
for duration of
.Fa period
milliseconds at given
.Fa volume .
Note that the
.Fa volume
value is ignored commonly.
.It Fn cnflush
Waits for all pending output to finish.
.It Fn cngetc
Poll (busy wait) for an input and return the input key.
Returns 0 if there is no console input device.
.Fn cnpollc
.Em must
be called before
.Fn cngetc
could be used.
.Fn cngetc
should be used during kernel startup only.
.It Fn cngetsn
Read one line of user input, stop reading once the newline
key is input.
Input is echoed back.
This uses
.Fn cnpollc
and
.Fn cngetc .
Number of read characters is
.Fa 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
.Fn cngetsn
discard input read so far, print newline and
wait for next input.
.Fn cngetsn
returns number of characters actually read, excluding
the final newline.
.Fa cp
is
.Em not
zero-ended before return.
.Fn cngetsn
should be used during kernel startup only.
.It Fn cnhalt
Terminates the console device (i.e. cleanly shuts down the console hardware.)
.It Fn cnpollc
Switch the console driver to polling mode if
.Fa on
is nonzero, or back to interrupt driven mode if
.Fa on
is zero.
.Fn cnpollc
should be used during kernel startup only.
.It Fn cnputc
Console kernel output character routine.
Commonly, kernel code uses
.Xr printf 9
rather than using this low-level interface.
.El
.Sh EXAMPLES
This waits until a <Enter> key is pressed:
.Pp
.Bd -literal -offset indent
int c;

cnpollc(1);
for(;;) {
	c = cngetc();
	if ((c == '\er' || (c == '\en')) {
		printf("\en");
		break;
	}
}
cnpollc(0);
.Ed
.Sh SEE ALSO
.Xr pckbd 4 ,
.Xr pcppi 4 ,
.Xr tty 4 ,
.Xr wscons 4 ,
.Xr wskbd 4 ,
.Xr printf 9 ,
.Xr spl 9 ,
.Xr wscons 9