ik.4

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)ik.4	8.1	9/11/90
.TH ik 4 VAX "" Unsupported
.SH Name
ik \- Ikonas frame buffer, graphics device interface
.SH Syntax
.B "device ik0 at uba? csr 0172460 vector ikintr"
.SH Description
The
.PN ik
program provides an interface to an Ikonas frame buffer graphics device.
Each minor device is a different frame buffer interface board.
When the device is opened, its interface registers are mapped,
by virtual memory, into the user processes address space.
This allows the user process very high bandwidth to the frame buffer
with no system call overhead.
.PP
Bytes written or read from the device are DMA'd from or to the interface.
The frame buffer XY address, its addressing mode, etc. must be set up by the
user process before calling write or read.
.PP
Other communication with the driver is by ioctls.
The IK_GETADDR ioctl returns the virtual address where the user process can
find the interface registers.
The IK_WAITINT ioctl suspends the user process until the ikonas device
has interrupted (for whatever reason \(em the user process has to set
the interrupt enables).
.SH Restrictions
An invalid access (for example, longword) to a mapped interface register
can cause the system to crash with a machine check.
.SH Files
.PN /dev/ik