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Driver Entry Pointsaread(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 5.9Go To TopLast Changed 28 Mar 1997

 
      
      
Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.