ps —
Evans and Sutherland Picture System 2 graphics device
  interface
ps0 at uba? csr 0172460 vector psclockintr pssystemintr
NOTE: This driver has not been ported from 4.4BSD yet.
The ps driver provides access to an Evans
    and Sutherland Picture System 2 graphics device. Each minor device is a new
    PS2. When the device is opened, its interface registers are mapped, via
    virtual memory, into a user process's address space. This allows the user
    process very high bandwidth to the device with no system call overhead.
DMA to and from the PS2 is not supported. All read and write
    system calls will fail. All data is moved to and from the PS2 via programmed
    I/O using the device's interface registers.
Commands are fed to and from the driver using the following
    ioctl(2)s:
  - PSIOGETADDR
- Returns the virtual address through which the user process can access the
      device's interface registers.
- PSIOAUTOREFRESH
- Start auto refreshing the screen. The argument is an address in user space
      where the following data resides. The first longword is a
      count of the number of static refresh buffers. The next
      count longwords are the addresses in refresh memory
      where the refresh buffers lie. The driver will cycle through these refresh
      buffers displaying them one by one on the screen.
- PSIOAUTOMAP
- Start automatically passing the display file through the matrix processor
      and into the refresh buffer. The argument is an address in user memory
      where the following data resides. The first longword is a
      count of the number of display files to operate on. The
      next count longwords are the address of these display
      files. The final longword is the address in refresh buffer memory where
      transformed coordinates are to be placed if the driver is not in double
      buffer mode (see below).
- PSIODOUBLEBUFFER
- Cause the driver to double buffer the output from the map that is going to
      the refresh buffer. The argument is again a user space address where the
      real arguments are stored. The first argument is the starting address of
      refresh memory where the two double buffers are located. The second
      argument is the length of each double buffer. The refresh mechanism
      displays the current double buffer, in addition to its static refresh
      lists, when in double buffer mode.
- PSIOSINGLEREFRESH
- Single step the refresh process. That is, the driver does not continually
      refresh the screen.
- PSIOSINGLEMAP
- Single step the matrix process. The driver does not automatically feed
      display files through the matrix unit.
- PSIOSINGLEBUFFER
- Turn off double buffering.
- PSIOTIMEREFRESH
- The argument is a count of the number of refresh interrupts to take before
      turning off the screen. This is used to do time exposures.
- PSIOWAITREFRESH
- Suspend the user process until a refresh interrupt has occurred. If in
      TIMEREFRESHmode, suspend until count refreshes
      have occurred.
- PSIOSTOPREFRESH
- Wait for the next refresh, stop all refreshes, and then return to user
      process.
- PSIOWAITMAP
- Wait until a map done interrupt has occurred.
- PSIOSTOPMAP
- Wait for a map done interrupt, do not restart the map, and then return to
      the user.
  - ps device intr.
- ps DMA intr.
- An interrupt was received from the device. This shouldn't happen, check
      your device configuration for overlapping interrupt vectors.
Theps 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.