1*42e22086SApple OSS Distributions<h2>device_read_overwrite_async</h2> 2*42e22086SApple OSS Distributions<hr> 3*42e22086SApple OSS Distributions<p> 4*42e22086SApple OSS Distributions<strong>System Trap</strong> - Read a sequence of bytes from a device object into the caller's 5*42e22086SApple OSS Distributions<h3>SYNOPSIS</h3> 6*42e22086SApple OSS Distributions<pre> 7*42e22086SApple OSS Distributions<strong>kern_return_t device_read_overwrite_async</strong> 8*42e22086SApple OSS Distributions <strong>(mach_port_t</strong> <var>device</var>, 9*42e22086SApple OSS Distributions <strong>mach_port_t</strong> <var>queue</var>, 10*42e22086SApple OSS Distributions <strong>mach_port_t</strong> <var>request_id</var>, 11*42e22086SApple OSS Distributions <strong>dev_mode_t</strong> <var>mode</var>, 12*42e22086SApple OSS Distributions <strong>recnum_t</strong> <var>recnum</var>, 13*42e22086SApple OSS Distributions <strong>io_buf_len_t</strong> <var>bytes_wanted</var>, 14*42e22086SApple OSS Distributions <strong>io_buf_ptr_t</strong> <var>buffer</var><strong>);</strong> 15*42e22086SApple OSS Distributions</pre> 16*42e22086SApple OSS Distributions<h3>PARAMETERS</h3> 17*42e22086SApple OSS Distributions<dl> 18*42e22086SApple OSS Distributions<p> 19*42e22086SApple OSS Distributions<dt> <var>device</var> 20*42e22086SApple OSS Distributions<dd> 21*42e22086SApple OSS Distributions[in device send right] A device port to the device to be read. 22*42e22086SApple OSS Distributions<p> 23*42e22086SApple OSS Distributions<dt> <var>queue</var> 24*42e22086SApple OSS Distributions<dd> 25*42e22086SApple OSS Distributions[in io_done queue send right] The port returned from the 26*42e22086SApple OSS Distributionsio_done_queue_create call. 27*42e22086SApple OSS Distributions<p> 28*42e22086SApple OSS Distributions<dt> <var>request_id</var> 29*42e22086SApple OSS Distributions<dd> 30*42e22086SApple OSS Distributions[in send right] An unique request identifier that will be passed back as 31*42e22086SApple OSS Distributionspart of the io_done_result structure. 32*42e22086SApple OSS Distributions<p> 33*42e22086SApple OSS Distributions<dt> <var>mode</var> 34*42e22086SApple OSS Distributions<dd> 35*42e22086SApple OSS Distributions[in scalar] I/O mode value. Meaningful options are: 36*42e22086SApple OSS Distributions<p> 37*42e22086SApple OSS Distributions <dl> 38*42e22086SApple OSS Distributions<dt> <strong>D_NOWAIT</strong> 39*42e22086SApple OSS Distributions<dd> 40*42e22086SApple OSS DistributionsDo not wait if data is unavailable. 41*42e22086SApple OSS Distributions<p> 42*42e22086SApple OSS Distributions </dl> 43*42e22086SApple OSS Distributions<dt> <var>recnum</var> 44*42e22086SApple OSS Distributions<dd> 45*42e22086SApple OSS Distributions[in scalar] Record number to be read. 46*42e22086SApple OSS Distributions<p> 47*42e22086SApple OSS Distributions<dt> <var>bytes_wanted</var> 48*42e22086SApple OSS Distributions<dd> 49*42e22086SApple OSS Distributions[in scalar] Size of data transfer. 50*42e22086SApple OSS Distributions<p> 51*42e22086SApple OSS Distributions<dt> <var>buffer</var> 52*42e22086SApple OSS Distributions<dd> 53*42e22086SApple OSS Distributions[pointer to in array of bytes] Data buffer to be overwritten. 54*42e22086SApple OSS Distributions</dl> 55*42e22086SApple OSS Distributions<h3>DESCRIPTION</h3> 56*42e22086SApple OSS Distributions<p> 57*42e22086SApple OSS DistributionsThe <strong>device_read_overwrite</strong> system trap enqueues a read operation for a 58*42e22086SApple OSS Distributionssequence of bytes from a device object to be placed directly into 59*42e22086SApple OSS Distributionsthe caller's address space. The meaning of recnum as well as the 60*42e22086SApple OSS Distributionsspecific operation performed is device dependent. 61*42e22086SApple OSS Distributions<h3>RETURN VALUES</h3> 62*42e22086SApple OSS Distributions<p> 63*42e22086SApple OSS Distributions<strong>device_read_overwrite_async</strong> returns only invalid parameter errors. 64*42e22086SApple OSS Distributions<h3>RELATED INFORMATION</h3> 65*42e22086SApple OSS Distributions<p> 66*42e22086SApple OSS DistributionsFunctions: 67*42e22086SApple OSS Distributions<a href="device_read_async.html"><strong>device_read_async</strong></a>, 68*42e22086SApple OSS Distributions<a href="device_read_async_inband.html"><strong>device_read_async_inband</strong></a>, 69*42e22086SApple OSS Distributions<a href="device_write_async.html"><strong>device_write_async</strong></a>, 70*42e22086SApple OSS Distributions<a href="device_write_async_inband.html"><strong>device_write_async_inband</strong></a>, 71*42e22086SApple OSS Distributions<a href="io_done_queue_create.html"><strong>io_done_queue_create</strong></a>. 72