Manual Pages for UNIX Operating System command usage for man aread

Driver Entry Points                                     aread(9E)



NAME
     aread - asynchronous read from a device

SYNOPSIS
     #include 
     #include 
     #include 
     #include 
     #include 
     intprefix

     aread(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)

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  asyn-
     chronous  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()  rou-
     tine  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




SunOS 5.11          Last change: 28 Mar 1997                    1






Driver Entry Points                                     aread(9E)



     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),      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 5.11          Last change: 28 Mar 1997                    2