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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>

       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. Driv‐
       ers 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 required privileges 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));
         }


SEE ALSO
       read(2),  aioread(3C),  awrite(9E),  read(9E), strategy(9E), write(9E),
       anocancel(9F), aphysio(9F), ddi_get_soft_state(9F), drv_priv(9F),  get‐
       minor(9F), minphys(9F), nodev(9F), cb_ops(9S), aio_req(9S), uio(9S)


       Writing Device Drivers in Oracle Solaris 11.4

BUGS
       There  is  no way other than calling aphysio(9F) to accomplish an asyn‐
       chronous read.



Oracle Solaris 11.4               3 Nov 2021                         aread(9E)
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