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>
int prefixaread(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). 

ARGUMENTS

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

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(3), 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 5.6  —  Last change: 28 Mar 1997