physio(9F)

NAME

     physio, minphys - perform physical I/O

SYNOPSIS

     #include <sys/types.h>
     #include <sys/buf.h>
     #include <sys/uio.h>

     int physio(int(*strat )(struct buf *), struct buf *bp, dev_t
     dev,  int  rw,  void  (*mincnt  )(struct  buf *), struct uio
     *uio);

     void minphys(struct buf *bp);

INTERFACE LEVEL

     Solaris DDI specific (Solaris DDI).

PARAMETERS

  physio()
     strat Pointer to device strategy routine.

     bp    Pointer  to  a  buf(9S)   structure   describing   the
           transfer. If bp is set to NULL then physio() allocates
           one which is automatically released upon completion.

     dev   The device number.

     rw    Read/write flag. This is either  B_READ  when  reading
           from  the  device, or B_WRITE when writing to the dev-
           ice.

     mincnt
           Routine which bounds the maximum transfer unit size.

     uio   Pointer to the uio structure which describes the  user
           I/O request.

  minphys()
     bp    Pointer to a buf structure.

DESCRIPTION

     physio() performs unbuffered I/O operations between the dev-
     ice  dev  and  the address space described in the uio struc-
     ture.

     Prior to the start of the  transfer  physio()  verifies  the
     requested  operation  is valid by checking the protection of
     the address space specified in the uio  structure.  It  then
     locks the pages involved in the I/O transfer so they can not
     be paged out. The device strategy routine, strat(), is  then
     called  one or more times to perform the physical I/O opera-
     tions. physio() uses biowait(9F) to block until strat()  has
     completed each transfer. Upon completion, or detection of an
     error, physio() unlocks the  pages  and  returns  the  error
     status.

     physio() uses mincnt() to bound the  maximum  transfer  unit
     size  to the system, or device, maximum length. minphys() is
     the system mincnt() routine for  use  with  physio()  opera-
     tions. Drivers which do not provide their own local mincnt()
     routines should call physio() with minphys().

     minphys() limits the value of  bp->b_bcount  to  a  sensible
     default  for  the  capabilities  of the system. Drivers that
     provide their own mincnt() routine  should  also  call  min-
     phys() to make sure they do not exceed the system limit.

RETURN VALUES

     physio() returns:

     0     Upon success.

     non-zero
           Upon failure.

CONTEXT

     physio() can be called from user context only.

SEE ALSO

     strategy(9E), biodone(9F), biowait(9F), buf(9S), uio(9S)

     Writing Device Drivers

WARNINGS

     Since physio() calls  biowait()  to  block  until  each  buf
     transfer  is  complete,  it is the drivers responsibility to
     call biodone(9F) when the transfer is complete, or  physio()
     will block forever.