A pointer to a caller-provided MMIOINFO
structure containing extra parameters used by mmioOpen. Only certain
values of the MMIOINFO structure
may be used as input to the mmioOpen function. These fields are fccIOProc,
pIOProc, cchBuffer, pchBuffer, aulInfo, and
ulTranslate. fccIOProc and pIOProc are used if you
wish to identify the I/O procedure to be used, rather than allowing MMIO
to determine the appropriate I/O procedure. cchBuffer and pchBuffer
are used for buffered access. aulInfo can contain a media type
which restricts the open to I/O procedures of that type. ulTranslate
is used to specify whether or not translation of header and data is
performed.
The pmmioinfo parameter can be NULL if the default values of the
fields of MMIOINFO are sufficient.
All unused fields must be set to 0, including reserved fields. (The easiest
way to do this is to fill the structure with NULL bytes before setting the
desired fields.) See the MMIOINFO
data structure for more information. mmioOpen will modify the ulErrorRet
field of MMIOINFO if an error
is encountered.