sunos man page for read

read(9E)							Driver Entry Points							  read(9E)

NAME
       read - read data from a device

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

       int prefixread(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
       The driver  read() routine is called indirectly through cb_ops(9S) by the  read(2) system call. The  read() routine should check the valid-
       ity of the minor number component of dev and the user credential structure pointed to by   cred_p  (if  pertinent).   The   read()  routine
       should supervise the data transfer into the user space described by the	uio(9S) structure.

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

EXAMPLES
       Example 1: read() routine using physio()

       The following is an example of a read() routine using physio(9F) to perform reads from a non-seekable device:

	     static int
	     xxread(dev_t dev, struct uio *uiop, cred_t *credp)
	     {
		      int		  rval;
		      offset_t		  off;
		      int		  instance;
		      xx_t		  xx;

		      instance = getminor(dev);
		      xx = ddi_get_soft_state(xxstate, instance);
		      if (xx == NULL)
				return (ENXIO);
		      off = uiop->uio_loffset;
		      rval = physio(xxstrategy, NULL, dev, B_READ,
				xxmin, uiop);
		      uiop->uio_loffset = off;
		      return (rval);
	     }

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

       Writing Device Drivers

SunOS 5.10							    19 Nov 1997 							  read(9E)