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);

        /* Verifysoft 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.