ik(4) - NetBSD Manual Pages

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IK(4)                 NetBSD/vax Kernel Interfaces Manual                IK(4)

ik -- Ikonas frame buffer, graphics device interface
ik0 at uba? csr 0172460 vector ikintr
NOTE: This driver has not been ported from 4.4BSD yet. The ik driver 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, via vir- tual memory, into the user processes address space. This allows the user process very high bandwidth to the frame buffer with no system call over- head. Bytes written or read from the device are DMA'ed from or to the inter- face. The frame buffer XY address, its addressing mode, etc. must be set up by the user process before calling write or read. Other communication with the driver is via ioctls. The IK_GETADDR ioctl(2) returns the virtual address where the user process can find the interface registers. The IK_WAITINT ioctl(2) suspends the user process until the ikonas device has interrupted (for whatever reason -- the user process has to set the interrupt enables).
The ik driver appeared in 4.2BSD.
An invalid access (e.g., longword) to a mapped interface register can cause the system to crash with a machine check. A user process could possibly cause infinite interrupts hence bringing things to a crawl. NetBSD 9.0 June 5, 1993 NetBSD 9.0
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