osfmk/man/DR_overwrite_async.html

   1 <h2>device_read_overwrite_async</h2>
   2 <hr>
   3 <p>
   4 <strong>System Trap</strong> - Read a sequence of bytes from a device object into the caller's
   5 <h3>SYNOPSIS</h3>
   6 <pre>
   7 <strong>kern_return_t   device_read_overwrite_async</strong>
   8                 <strong>(mach_port_t</strong>                             <var>device</var>,
   9                  <strong>mach_port_t</strong>                              <var>queue</var>,
  10                  <strong>mach_port_t</strong>                         <var>request_id</var>,
  11                  <strong>dev_mode_t</strong>                                <var>mode</var>,
  12                  <strong>recnum_t</strong>                                <var>recnum</var>,
  13                  <strong>io_buf_len_t</strong>                      <var>bytes_wanted</var>,
  14                  <strong>io_buf_ptr_t</strong>                            <var>buffer</var><strong>);</strong>
  15 </pre>
  16 <h3>PARAMETERS</h3>
  17 <dl>
  18 <p>
  19 <dt> <var>device</var>
  20 <dd>
  21 [in device send right] A device port to the device to be read.
  22 <p>
  23 <dt> <var>queue</var>
  24 <dd>
  25 [in io_done queue send right] The port returned from the
  26 io_done_queue_create call.
  27 <p>
  28 <dt> <var>request_id</var>
  29 <dd>
  30 [in send right] An unique request identifier that will be passed back as
  31 part of the io_done_result structure.
  32 <p>
  33 <dt> <var>mode</var>
  34 <dd>
  35 [in scalar] I/O mode value. Meaningful options are:
  36 <p>
  37      <dl>
  38 <dt> <strong>D_NOWAIT</strong>
  39 <dd>
  40 Do not wait if data is unavailable.
  41 <p>
  42      </dl>
  43 <dt> <var>recnum</var>
  44 <dd>
  45 [in scalar] Record number to be read.
  46 <p>
  47 <dt> <var>bytes_wanted</var>
  48 <dd>
  49 [in scalar] Size of data transfer.
  50 <p>
  51 <dt> <var>buffer</var>
  52 <dd>
  53 [pointer to in array of bytes] Data buffer to be overwritten.
  54 </dl>
  55 <h3>DESCRIPTION</h3>
  56 <p>
  57 The <strong>device_read_overwrite</strong> system trap enqueues a read operation for a
  58 sequence of bytes from a device object to be placed directly into
  59 the caller's address space. The meaning of recnum as well as the
  60 specific operation performed is device dependent.
  61 <h3>RETURN VALUES</h3>
  62 <p>
  63 <strong>device_read_overwrite_async</strong> returns only invalid parameter errors.
  64 <h3>RELATED INFORMATION</h3>
  65 <p>
  66 Functions:
  67 <a href="device_read_async.html"><strong>device_read_async</strong></a>,
  68 <a href="device_read_async_inband.html"><strong>device_read_async_inband</strong></a>,
  69 <a href="device_write_async.html"><strong>device_write_async</strong></a>,
  70 <a href="device_write_async_inband.html"><strong>device_write_async_inband</strong></a>,
  71 <a href="io_done_queue_create.html"><strong>io_done_queue_create</strong></a>.