Driver Entry Points                                  strategy(9E)



NAME
     strategy - perform block I/O

SYNOPSIS
     #include 
     #include 
     #include 
     #include 



     int prefixstrategy(struct buf *bp);


INTERFACE LEVEL
     Architecture independent level 1 (DI/DKI). This entry point
     is required for block devices.

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


DESCRIPTION
     The  strategy()  routine  is  called   indirectly   (through
     cbops(9S))  by  the kernel to read and write blocks of data
     on the block device. strategy() may also be called  directly
     or  indirectly  to  support the raw character interface of a
     block device (read(9E), write(9E) and ioctl(9E)). The  stra-
     tegy()  routine's  responsibility  is to set up and initiate
     the transfer.


     In general, strategy() should not block.  It  can,  however,
     perform  a  kmemcachecreate(9F)  with both the KMPUSHPAGE
     and KMSLEP flags set, which might block,  without  causing
     deadlock in low memory situations.

RETURN VALUES
     The strategy() function must return 0. On  an  error  condi-
     tion,  it  should  call  bioerror(9F)  to set bflags to the
     proper error code, and call biodone(9F). Note that a partial
     transfer is not considered to be an error.

SEE ALSO
     ioctl(9E), read(9E), write(9E),  biodone(9F),  bioerror(9F),
     buf(9S), cbops(9S), kmemcachecreate(9F)


     Writing Device Drivers






SunOS 5.11           Last change: 6 Nov 2003                    1