illumos: manual page: aread.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

illumos DDI specific (illumos 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));
}

BUGS

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

March 28, 1997 AREAD(9E)