AREAD(9E) Driver Entry Points AREAD(9E)

aread - asynchronous read from a device

#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);

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

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.

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.

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

This function is called from user context only.

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));
}

read(2), aioread(3C), 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

There is no way other than calling aphysio(9F) to accomplish an asynchronous read.
March 28, 1997 OmniOS