WRITE(9E) Driver Entry Points WRITE(9E)

write - write data to a device

#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);

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

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.

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 pertinent.

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

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));
}

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

Writing Device Drivers

March 28, 1997 OmniOS