usrvme(7M)

NAME
     usrvme - User level VME Bus adapter interface.


DESCRIPTION
     The usrvme interface provides access to VME bus address spaces from user
     processes.


   Challenge and Onyx Systems
     On Challenge and Onyx systems, access to VME bus address spaces are
     provided by special files.  They're named according to the following
     convention:

     /dev/vme/vme<adapter>a<address-space><address-mode>

     <adapter> is the number of VME bus adapter.
     <address-space> is one of {16, 24, 32}.
     <address-mode> is either n for non-privileged or s for supervisory.

     For instance, address space 16 in non-privileged mode on adapter 0 would
     be referred to as /dev/vme/vme0a16n.

     The kernel driver for user level VME is referred to as usrvme.  If VME
     busses are added to an existing system, it may be necessary to run
     MAKEDEV(1M) specifying a target of usrvme in order to have the additional
     /dev/vme devices created.


   Origin2000 and Onyx2 Systems
     On Origin2000 and Onyx2 systems, VME bus address spaces can be accessed
     by hardware graph vertices.  The vertices are named by the following
     convention:

     /hw/vme/<adapter>/usrvme/<address-space>/<data-width>

     <adapter> is the number of VME bus adapter.
     <address-space> is the code for address space.  It could be one of
     {a32s,a32n, a24s, a24n, a16s, a16n}.
     <data-width> is the maximum PIO data width on VME bus.  It could be one
     of {d64, d32, d16, d8} in A32 space, or one of {d32, d16, d16, d8} in A24
     and A16 spaces.


   Error Handling
     Not all addresses can be read from or written to because of read-only or
     write-only registers and unequipped addresses. Reads or writes to invalid
     VME bus addresses will normally result in a SIGBUS signal being sent to
     the offending process.

     On CHALLENGE, ONYX, Origin2000, and ONYX2 systems, writes to an invalid
     VME bus address are asynchronous, processor does not wait for the
     completion of write operation.  If write operation fails, it could take
     up to 10 millisecs for the user VME process to be signalled about failed
     write.  (Note that VME bus timeout is about 80 microsecs on Challenge and
     Onyx systems, 64 microseconds on Origin2000 and Onyx2 systems.)  So, if
     the user VME process has to confirm that the write completed
     successfully, it should wait for about 10 millisecs.  If the user VME
     process has already terminated by the time kernel gets the VME write
     error interrupt, a message is sent to SYSLOG indicating the VME Adapter
     number, and failed VME bus address.

     If multiple processes have the mapping for the VME address which got an
     error, all of them would be sent SIGBUS signal.


SEE ALSO
     "IRIX Device Driver Programmer's Guide"
     hinv(1M)
     MAKEDEV(1M) -- on Challenge and Onyx systems.