VGA(3) VGA(3)
NAME
vga - VGA controller device
SYNOPSIS
bind #v /dev
/dev/vgactl
/dev/vgaiob
/dev/vgaiow
/dev/vgaiol
DESCRIPTION
The VGA device allows configuration of a graphics controller
on a PC. Vgactl allows control over higher-level settings
such as display height, width, depth, controller and
hardware-cursor type. Vgaiob, vgaiow and vgaiol allow con-
trol 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 func-
tions are normally carried out by vga(8).
Writes to vgactl are of the form `attribute value'. Valid
attributes are
size value is 'XxYxZ' , where X, Y and Z are numbers that
tell the kernel the width and height of the screen in
pixels and the number of bits per pixel.
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 vga, clgd542x, et4000, mach32, and
s3 are supported for value.
Note that this list does not indicate the full set of
VGA chips supported. For example, s3 includes the
86C801/5, 86C928, Vision864, and Vision964. It is the
job of vga(8) to recognize which particular chip is
being used and to initialize it appropriately.
hwgc tells the kernel to use a particular type of hardware
graphics cursor. Bt485hwgc, et4000hwgc, s3hwgc and
tvp3020hwgc, are currently recognized values. A value
of off reverts to using the software cursor.
Reading vgactl returns the current settings, one per line.
EXAMPLES
The following reverts to using the software graphics cursor
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VGA(3) VGA(3)
echo -n 'hwgc off' >/dev/vgactl
Sample code to read an x86 8-bit I/O port
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): %r0, port);
return data;
}
SOURCE
/sys/src/9/pc/devvga.c
SEE ALSO
vga(8)
BUGS
There should be some restriction on the range of valid
ports.
There should be support for the hardware graphics cursor on
the clgd54[23]x VGA controller chips.
The hardware graphics cursor on the et4000 does not work in
2x8-bit mode.
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