.TH VGA 3 
.SH NAME
vga \- VGA controller device
.SH SYNOPSIS
.nf
.B bind #v /dev

.B /dev/vgactl
.B /dev/vgaiob
.B /dev/vgaiow
.B /dev/vgaiol
.fi
.SH DESCRIPTION
The VGA device allows configuration of a graphics controller
on a PC.
.B Vgactl
allows control over higher-level settings such as display height, width, depth,
controller and hardware-cursor type.
.BR Vgaiob ,
.B vgaiow 
and
.B vgaiol
allow control over individual 8-bit, 16-bit and 32-bit
x86
I/O-ports respectively, such as those
used to implement configuration and setup registers on a VGA controller card.
These functions are normally carried out by
.IR vga (8).
.PP
Writes to
.B vgactl
are of the form
.RI ` attribute\ value '.
Valid attributes are
.TP
.I size
.I value
is 
.IB 'X x Y x Z'
, where
.IR X ,
.I Y
and
.I Z
are numbers that tell the kernel the width and
height of the screen in pixels and the number of
bits per pixel.
.TP
.I type
tells the kernel which type of controller is
being used, mainly to enable the correct code for display-memory bank switching
at resolutions greater than 640x480x1. The names
.IR vga ,
.IR clgd542x ,
.IR et4000 ,
.IR mach32 ,
and
.I s3
are supported for
.IR value .
.IP
Note that this list does not indicate the full set of VGA chips
supported. For example,
.I s3
includes the 86C801/5, 86C928, Vision864, and Vision964.
It is the job of
.IR vga (8)
to recognize which particular chip is being used and to initialize it
appropriately.
.TP
.I hwgc
tells the kernel to use a particular type of hardware graphics cursor.
.IR Bt485hwgc ,
.IR et4000hwgc ,
.I s3hwgc
and
.IR tvp3020hwgc ,
are currently recognized values.
A value of
.I off
reverts to using the software cursor.
.PP
Reading
.B vgactl
returns the current settings, one per line.
.SH EXAMPLES
The following reverts to using the software graphics
cursor
.EX

	echo -n 'hwgc off' >/dev/vgactl

.EE
Sample code to read an
x86
8-bit I/O port
.EX

	uchar
	inportb(long port)
	{
		uchar data;
	
		if(iobfd == -1)
			iobfd = open("#v/vgaiob", ORDWR);
	
		seek(iobfd, port, 0);
		if(read(iobfd, &data, sizeof(data)) != sizeof(data))
			error("inportb(0x%4.4x): %r\n", port);
		return data;
	}

.EE
.SH SOURCE
.B /sys/src/9/pc/devvga.c
.SH SEE ALSO
.IR vga (8)
.SH BUGS
There should be some restriction on the range of valid ports.
.PP
There should be support for the hardware graphics cursor on the
.I clgd54[23]x
VGA controller chips.
.PP
The hardware graphics cursor on the
.I et4000
does not work in 2x8-bit mode.