AWRITE(9E) Driver Entry Points AWRITE(9E)

NAME


awrite - asynchronous write to 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 prefixawrite(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 awrite() 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 stored.


cred_p
Pointer to the credential structure.


DESCRIPTION


The driver's awrite() routine is called to perform an asynchronous write.
getminor(9F) can be used to access the minor number component of the dev
argument. awrite() may use the credential structure pointed to by cred_p
to check for superuser access by calling drv_priv(9F). The awrite()
routine may also examine the uio(9S) structure through the aio_req
structure pointer, aio_reqp. awrite() 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 awrite() routine should return 0 for success, or the appropriate
error number.

CONTEXT


This function is called from user context only.

EXAMPLES


Example 1: Using the awrite() routine:




The following is an example of an awrite() routine:


static int
xxawrite(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_WRITE, \
xxminphys, aio));
}


SEE ALSO


write(2), aiowrite(3C), aread(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 write.

illumos February 15, 2020 AWRITE(9E)