read(9e) [opensolaris man page]

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 5.11							    19 Nov 1997 							  read(9E)

aread(9E)							Driver Entry Points							 aread(9E)

NAME

       aread - asynchronous read from a device

SYNOPSIS

       #include <sys/uio.h>
       #include <sys/aio_req.h>
       #include <sys/cred.h>
       #include <sys/ddi.h>
       #include <sys/sunddi.h>
       intprefix

       aread(dev_t dev, struct aio_req *aio_reqp, cred_t *cred_p);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI). This entry point is optional. Drivers that do not support an aread() entry point should use nodev(9F)

PARAMETERS

       dev	       Device number.

       aio_reqp        Pointer to the aio_req(9S) structure that describes where the data is to be stored.

       cred_p	       Pointer to the credential structure.

DESCRIPTION

       The  driver's  aread()  routine is called to perform an asynchronous read. getminor(9F) can be used to access the minor number component of
       the dev argument. aread() may use the credential structure pointed to by cred_p to check for superuser access by calling drv_priv(9F).  The
       aread()	routine may also examine the uio(9S) structure through the aio_req structure pointer, aio_reqp. aread() must call aphysio(9F) with
       the aio_req pointer and a pointer to the driver's strategy(9E) routine.

       No fields of the uio(9S) structure pointed to by aio_req, other than uio_offset or uio_loffset, may be modified for non-seekable devices.

RETURN VALUES

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

CONTEXT

       This function is called from user context only.

EXAMPLES

       Example 1: The following is an example of an aread() routine:

       static int
       xxaread(dev_t dev, struct aio_req *aio, cred_t *cred_p)
       {
	    int instance;
	    struct xxstate *xsp;
	    instance = getminor(dev);
	    xsp = ddi_get_soft_state(statep, instance);
	    /*Verify soft state structure has been allocated */
	    if (xsp == NULL)
		 return (ENXIO);
	    return (aphysio(xxstrategy, anocancel,
				dev, B_READ, xxminphys, aio));
       }

SEE ALSO

       read(2), aioread(3AIO), awrite(9E), read(9E), strategy(9E), write(9E), anocancel(9F),  aphysio(9F),  ddi_get_soft_state(9F),  drv_priv(9F),
       getminor(9F), minphys(9F), nodev(9F), aio_req(9S), cb_ops(9S), uio(9S)

       Writing Device Drivers

BUGS

       There is no way other than calling aphysio(9F) to accomplish an asynchronous read.

SunOS 5.10							    28 Mar 1997 							 aread(9E)