1*699cd480SApple OSS Distributions<h2>device_read_async</h2> 2*699cd480SApple OSS Distributions<hr> 3*699cd480SApple OSS Distributions<p> 4*699cd480SApple OSS Distributions<strong>System Trap</strong> - Read a sequence of bytes from a device object. 5*699cd480SApple OSS Distributions<h3>SYNOPSIS</h3> 6*699cd480SApple OSS Distributions<pre> 7*699cd480SApple OSS Distributions<strong>kern_return_t device_read_async</strong> 8*699cd480SApple OSS Distributions <strong>(mach_port_t</strong> <var>device</var>, 9*699cd480SApple OSS Distributions <strong>mach_port_t</strong> <var>queue</var>, 10*699cd480SApple OSS Distributions <strong>mach_port_t</strong> <var>request_id</var>, 11*699cd480SApple OSS Distributions <strong>dev_mode_t</strong> <var>mode</var>, 12*699cd480SApple OSS Distributions <strong>recnum_t</strong> <var>recnum</var>, 13*699cd480SApple OSS Distributions <strong>io_buf_len_t</strong> <var>bytes_wanted</var><strong>);</strong> 14*699cd480SApple OSS Distributions</pre> 15*699cd480SApple OSS Distributions<h3>PARAMETERS</h3> 16*699cd480SApple OSS Distributions<dl> 17*699cd480SApple OSS Distributions<p> 18*699cd480SApple OSS Distributions<dt> <var>device</var> 19*699cd480SApple OSS Distributions<dd> 20*699cd480SApple OSS Distributions[in device send right] A device port to the device to be read. 21*699cd480SApple OSS Distributions<p> 22*699cd480SApple OSS Distributions<dt> <var>queue</var> 23*699cd480SApple OSS Distributions<dd> 24*699cd480SApple OSS Distributions[in io_done queue send right] The port returned from 25*699cd480SApple OSS Distributionsio_done_queue_create. 26*699cd480SApple OSS Distributions<p> 27*699cd480SApple OSS Distributions<dt> <var>request_id</var> 28*699cd480SApple OSS Distributions<dd> 29*699cd480SApple OSS Distributions[in send right] An unique request identifier that will be passed back as 30*699cd480SApple OSS Distributionspart of the io_done_result structure. 31*699cd480SApple OSS Distributions<p> 32*699cd480SApple OSS Distributions<dt> <var>mode</var> 33*699cd480SApple OSS Distributions<dd> 34*699cd480SApple OSS Distributions[in scalar] I/O mode value. Meaningful options are: 35*699cd480SApple OSS Distributions<p> 36*699cd480SApple OSS Distributions <dl> 37*699cd480SApple OSS Distributions<dt> <strong>D_NOWAIT</strong> 38*699cd480SApple OSS Distributions<dd> 39*699cd480SApple OSS DistributionsDo not wait if data is unavailable. 40*699cd480SApple OSS Distributions </dl> 41*699cd480SApple OSS Distributions<p> 42*699cd480SApple OSS Distributions<dt> <var>recnum</var> 43*699cd480SApple OSS Distributions<dd> 44*699cd480SApple OSS Distributions[in scalar] Record number to be read. 45*699cd480SApple OSS Distributions<p> 46*699cd480SApple OSS Distributions<dt> <var>bytes_wanted</var> 47*699cd480SApple OSS Distributions<dd> 48*699cd480SApple OSS Distributions[in scalar] Size of data transfer. 49*699cd480SApple OSS Distributions</dl> 50*699cd480SApple OSS Distributions<h3>DESCRIPTION</h3> 51*699cd480SApple OSS Distributions<p> 52*699cd480SApple OSS DistributionsThe <strong>device_read_async</strong> interface enqueues a read operation for a 53*699cd480SApple OSS Distributionssequence of bytes from a device object. The meaning of recnum as well 54*699cd480SApple OSS Distributionsas the specific operation performed is device dependent. 55*699cd480SApple OSS Distributions<h3>RETURN VALUES</h3> 56*699cd480SApple OSS Distributions<dl> 57*699cd480SApple OSS Distributions<strong>device_read_async</strong> returns only invalid parameter errors. 58*699cd480SApple OSS Distributions<dd> 59*699cd480SApple OSS Distributions</dl> 60*699cd480SApple OSS Distributions<h3>RELATED INFORMATION</h3> 61*699cd480SApple OSS Distributions<p> 62*699cd480SApple OSS DistributionsFunctions: 63*699cd480SApple OSS Distributions<a href="device_read_async_inband.html"><strong>device_read_async_inband</strong></a>, 64*699cd480SApple OSS Distributions<a href="DR_overwrite_async.html"><strong>device_read_overwrite_async</strong></a>, 65*699cd480SApple OSS Distributions<a href="device_write_async.html"><strong>device_write_async</strong></a>, 66*699cd480SApple OSS Distributions<a href="device_write_async_inband.html"><strong>device_write_async_inband</strong></a>, 67*699cd480SApple OSS Distributions<a href="io_done_queue_create.html"><strong>io_done_queue_create</strong></a>. 68