Kernel Functions for Drivers                          biodone(9F)



NAME
     biodone - release  buffer  after  buffer  I/O  transfer  and
     notify blocked threads

SYNOPSIS
     #include 
     #include 



     void biodone(struct buf *bp);


INTERFACE LEVEL
     Architecture independent level 1 (DI/DKI).

PARAMETERS
     bp    Pointer to a buf(9S) structure.


DESCRIPTION
     The biodone() function notifies  blocked  processes  waiting
     for the I/O to complete, sets the BDONE flag in the bflags
     field of the buf(9S) structure, and releases the  buffer  if
     the  I/O  is asynchronous. biodone() is called by either the
     driver interrupt or strategy(9E) routines when a buffer  I/O
     request is complete.


     The biodone() function provides the  capability  to  call  a
     completion  routine  if  bp  describes  a kernel buffer. The
     address of the routine is specified in the biodone field of
     the  buf(9S)  structure.  If  such  a  routine is specified,
     biodone() calls it and returns without performing any  other
     actions. Otherwise, it performs the steps above.

CONTEXT
     The biodone() function can be called from  user,  interrupt,
     or kernel context.

EXAMPLES
     Generally, the first validation test performed by any  block
     device  strategy(9E)  routine  is a check for an end-of-file
     (EOF) condition. The strategy(9E) routine is responsible for
     determining  an  EOF  condition  when the device is accessed
     directly. If a read(2) request is made for one block  beyond
     the  limits  of  the device (line 10), it will report an EOF
     condition.  Otherwise, if the request is outside the  limits
     of  the  device, the routine will report an error condition.
     In either case, report the I/O operation as  complete  (line
     27).




SunOS 5.11          Last change: 16 Jan 2006                    1






Kernel Functions for Drivers                          biodone(9F)



        1   #define RAMDNBLK    1000 /* Number of blocks in RAM disk */
        2   #define RAMDBSIZ    512  /* Number of bytes per block */
        3   char ramdblks[RAMDNBLK][RAMDBSIZ]; /* Array containing RAM disk */
        4
        5   static int
        6   ramdstrategy(struct buf *bp)
        7   {
        8      daddrt blkno = bp->bblkno;    /* get block number */
        9
       10      if ((blkno < 0)  (blkno >= RAMDNBLK)) {
       11            /*
       12             * If requested block is outside RAM disk
       13             * limits, test for EOF which could result
       14             * from a direct (physio) request.
       15             */
       16            if ((blkno == RAMDNBLK) && (bp->bflags & BREAD)) {
       17             /*
       18              * If read is for block beyond RAM disk
       19              * limits, mark EOF condition.
       20              */
       21              bp->bresid = bp->bbcount;  /* compute return value */
       22
       23           } else {    /* I/O attempt is beyond */
       24              bp->berror = ENXIO;    /*    limits of RAM disk */
       25              bp->bflags = BEROR; /* return error */
       26           }
       27           biodone(bp);     /* mark I/O complete (BDONE) */
       28             /*
       29              * Wake any processes awaiting this I/O
       30              * or release buffer for asynchronous
       31              * (BASYNC) request.
       32              */
       33           return (0);
       34      }
                  ...


SEE ALSO
     read(2),   strategy(9E),   biowait(9F),    ddiaddintr(9F),
     delay(9F), timeout(9F), untimeout(9F), buf(9S)


     Writing Device Drivers

WARNINGS
     After calling biodone(), bp is no  longer  available  to  be
     referred to by the driver. If the driver makes any reference
     to bp after calling biodone(), a panic may result.

NOTES
     Drivers that use the biodone field of the buf(9S) structure
     to  specify  a substitute completion routine should save the



SunOS 5.11          Last change: 16 Jan 2006                    2






Kernel Functions for Drivers                          biodone(9F)



     value of biodone before changing it, and then  restore  the
     old value before calling biodone() to release the buffer.





















































SunOS 5.11          Last change: 16 Jan 2006                    3