VGA(3)VGA(3)

NAME

vga – VGA controller device

SYNOPSIS

bind #v /dev

/dev/vgabios /dev/vgactl /dev/vgaovl /dev/vgaovlctl

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. Along with the I/O-port registers provided by arch(3), it is used to implement configuration and setup of VGA controller cards. This is usually performed by vga(8).

Vgabios provides read-only access to the low 640kB of memory, where the VGA and other BIOS ROMs are located.

Writing strings to vgactl configures the VGA device. The following are valid commands.

size X x Y x Z chan

Set the size of the screen image to be X pixels wide and Y pixels high. Each pixel is Z bits as specified by chan, whose format is described in image(6).  

actualsize X x Y

Set the physical size of the display to be X pixels wide by Y pixels high. This message is optional; it is used to implement panning and to accommodate displays that require the in-memory screen image to have certain alignment properties. For example, a 1400x1050 screen with a 1408x1050 in-memory image will use size 1408x1050 but actualsize 1400x1050 .  

panning mode

Depending on whether mode is on or off, enable or disable panning in a virtual screen. If panning is on and the screen’s size is larger than its actualsize, the displayed portion of the screen will pan to follow the mouse. Setting the panning mode after the first attach of the #i driver has no effect.  

type ctlr

Set the type of VGA controller being used. Ctlr is one of 3dfx, ark200pv, clgd542x, clgd546x, ct65545, cyber938x, et4000, geode, hiqvideo, i81x, igfx, mach64xx, mga2164w, mga4xx, neomagic, nvidia, radeon, s3, t2r4 and vmware.  

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 gc

Set the type of hardware graphics cursor being used. Gc is one of soft, 3dfxhwgc, ark200pvhwgc, bt485hwgc, clgd542xhwgc, clgd546xhwgc, ct65545hwgc, cyber938xhwgc, et4000hwgc, geodehwgc, hiqvideohwgc, i81xhwgc, igfxhwgc, mga2164whwgc, mach64xxhwgc, neomagichwgc, nvidiahwgc, radeonhwgc, rgb524hwgc, s3hwgc, t2r4hwgc, tvp3020hwgc, tvp3026hwgc and vmwarehwgc. A value of off disables the cursor.  

palettedepth d

Set the number of bits of precision used by the VGA palette to d, which must be either 6 or 8.  

hwaccel mode

Depending on whether mode is on or off, enable or disable whether hardware acceleration (currently for rectangle filling and moving) used by the graphics engine. The default setting is on.  

softscreen mode

Depending on whether mode is on or off, enable or disable shadow framebuffer to reduce slow bus reads. Enabling softscreen disables hardware acceleration. The default setting is off except for the vesa driver.  

hwblank mode

Depending on whether mode is on or off, enable or disable the use of DPMS blanking (see mouse(3)).  

linear size align

Use a linear screen aperture of size size aligned on an align-byte boundary.  

drawinit

Initialize the graphics hardware. This must be sent after setting the type.  

Reading vgactl returns the current settings, one per line.

Some VGA cards support overlay graphics. Writing strings to vgaovlctl configures such cards. The following are valid overlay control commands:

openctl

opens the overlay device.  

configure w h format

allocates resources inside the driver to support an overlay area of width w and height h pixels. Currently, the only supported format is YUYV packed. In YUYV two pixels are encoded by their separate Y values and their combined U and V values. The size of the two pixels is 32 bits.  

enable x y w h

enables drawing data on the display through the overlay mode. The data is drawn at position x,y and has a width and height of w,h respectively.  

closectl

terminates overlay control.  

Overlay data can be written to vgaovl.

EXAMPLES

The following disables hardware acceleration.

 

echo hwaccel off > /dev/vgactl

SOURCE

/sys/src/9/pc/devvga.c

SEE

arch(3), vga(8)

BUGS

The hardware graphics cursor on the et4000 does not work in 2x8-bit mode.