fbio - frame buffer control operations


     The frame buffers provided with  this  release  support  the
     same  general  interface  that  is defined by  <sys/fbio.h>.
     Each responds to an FBIOGTYPE ioctl(2) request which returns
     information in a fbtype structure.

     Each device has an FBTYPE  which  is  used  by  higher-level
     software  to  determine  how  to perform graphics functions.
     Each device is  used  by  opening  it,  doing  an  FBIOGTYPE
     ioctl()  to  see  which  frame  buffer  type is present, and
     thereby selecting  the  appropriate  device-management  rou-

     FBIOGINFO returns information specific to the  GS  accelera-

     FBIOSVIDEO  and  FBIOGVIDEO  are   general-purpose   ioctl()
     requests  for  controlling  possible video features of frame
     buffers. These ioctl() requests either  set  or  return  the
     value of a flags integer. At this point, only the FBVIDEO_ON
     option is available, controlled  by  FBIOSVIDEO.  FBIOGVIDEO
     returns the current video state.

     The FBIOSATTR and FBIOGATTR ioctl() requests allow access to
     special  features  of  newer  frame  buffers.  They  use the
     fbsattr and fbgattr structures.

     Some  color  frame  buffers  support  the  FBIOPUTCMAP   and
     FBIOGETCMAP  ioctl()  requests,  which provide access to the
     colormap. They use the fbcmap structure.

     Also, some framebuffers with multiple colormaps will  either
     encode the colormap identifier in the high-order bits of the
     "index"  field  in  the  fbcmap  structure,   or   use   the
     FBIOPUTCMAPI and FBIOGETCMAPI ioctl() requests.

     FBIOVERTICAL is used to wait for the start of the next vert-
     ical retrace period.

     FBIOVRTOFFSET Returns the offset  to  a  read-only  vertical
     retrace  page  for those framebuffers that support it.  This
     vertical retrace page may be mapped  into  user  space  with
     mmap(2).  The  first word of the vertical retrace page (type
     unsigned int) is a counter that is  incremented  every  time
     there  is a vertical retrace.  The user process can use this
     counter in a variety of ways.

     FBIOMONINFO returns  a  mon_info  structure  which  contains
     information  about  the monitor attached to the framebuffer,
     if available.

     used  to  control the hardware cursor for those framebuffers
     that have this  feature.  FBIOGCURMAX  returns  the  maximum
     sized  cursor  supported  by  the  framebuffer.  Attempts to
     create a cursor larger than this will fail.

     Finally FBIOSDEVINFO and FBIOGDEVINFO are used  to  transfer
     variable-length, device-specific information into and out of


     ioctl(2),  mmap(2),  bwtwo(7D),   cgeight(7D),   cgfour(7D),
     cgsix(7D), cgthree(7D), cgtwo(7D)


     The FBIOSATTR and FBIOGATTR ioctl() requests are  only  sup-
     ported  by  frame  buffers  which emulate older frame buffer
     types.  For  example,  cgfour(7D)  frame   buffers   emulate
     bwtwo(7D)  frame  buffers.  If  a  frame buffer is emulating
     another frame buffer, FBIOGTYPE returns the  emulated  type.
     To get the real type, use FBIOGATTR.

     The FBIOGCURPOS ioctl was incorrectly  defined  in  previous
     operating systems, and older code running in binary compati-
     bility mode may get incorrect results.

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