write(9E)							Driver Entry Points							 write(9E)

NAME

       write - write data to a device

SYNOPSIS

       #include <sys/types.h>
       #include <sys/errno.h>
       #include <sys/open.h>
       #include <sys/cred.h>
       #include <sys/ddi.h>
       #include <sys/sunddi.h>

       int prefixwrite(dev_t dev, struct uio *uio_p, cred_t *cred_p);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI). This entry point is optional.

PARAMETERS

       dev	  Device number.

       uio_p	  Pointer to the  uio(9S) structure that describes where the data is to be stored in user space.

       cred_p	  Pointer to the  user credential structure for the I/O transaction.

DESCRIPTION

       Used for character or raw data I/O, the driver  write() routine is called indirectly through  cb_ops(9S) by the	write(2) system call.  The
       write() routine supervises the data transfer from user space to a device described by the  uio(9S) structure.

       The  write() routine should check the validity of the minor number component of	dev and the user credentials pointed to by cred_p, if per-
       tinent.

RETURN VALUES

       The  write() routine should return 0 for success, or the appropriate error number.

EXAMPLES

       The following is an example of a write() routine using physio(9F) to perform writes to a seekable device:

	 static int
	 xxwrite(dev_t dev, struct uio *uiop, cred_t *credp)
	 {
	       int instance;
	       xx_t	xx;

	       instance = getminor(dev);
	       xx = ddi_get_soft_state(xxstate, instance);
	       if (xx == NULL)
		      return (ENXIO);
	       return (physio(xxstrategy, NULL, dev, B_WRITE,
		      xxmin, uiop));
	 }

SEE ALSO

       read(2), write(2), read(9E), physio(9F), cb_ops(9S), uio(9S)

       Writing Device Drivers

SunOS 5.11							    28 Mar 1997 							 write(9E)