1*33de042dSApple OSS Distributions<h2>device_read_async</h2> 2*33de042dSApple OSS Distributions<hr> 3*33de042dSApple OSS Distributions<p> 4*33de042dSApple OSS Distributions<strong>System Trap</strong> - Read a sequence of bytes from a device object. 5*33de042dSApple OSS Distributions<h3>SYNOPSIS</h3> 6*33de042dSApple OSS Distributions<pre> 7*33de042dSApple OSS Distributions<strong>kern_return_t device_read_async</strong> 8*33de042dSApple OSS Distributions <strong>(mach_port_t</strong> <var>device</var>, 9*33de042dSApple OSS Distributions <strong>mach_port_t</strong> <var>queue</var>, 10*33de042dSApple OSS Distributions <strong>mach_port_t</strong> <var>request_id</var>, 11*33de042dSApple OSS Distributions <strong>dev_mode_t</strong> <var>mode</var>, 12*33de042dSApple OSS Distributions <strong>recnum_t</strong> <var>recnum</var>, 13*33de042dSApple OSS Distributions <strong>io_buf_len_t</strong> <var>bytes_wanted</var><strong>);</strong> 14*33de042dSApple OSS Distributions</pre> 15*33de042dSApple OSS Distributions<h3>PARAMETERS</h3> 16*33de042dSApple OSS Distributions<dl> 17*33de042dSApple OSS Distributions<p> 18*33de042dSApple OSS Distributions<dt> <var>device</var> 19*33de042dSApple OSS Distributions<dd> 20*33de042dSApple OSS Distributions[in device send right] A device port to the device to be read. 21*33de042dSApple OSS Distributions<p> 22*33de042dSApple OSS Distributions<dt> <var>queue</var> 23*33de042dSApple OSS Distributions<dd> 24*33de042dSApple OSS Distributions[in io_done queue send right] The port returned from 25*33de042dSApple OSS Distributionsio_done_queue_create. 26*33de042dSApple OSS Distributions<p> 27*33de042dSApple OSS Distributions<dt> <var>request_id</var> 28*33de042dSApple OSS Distributions<dd> 29*33de042dSApple OSS Distributions[in send right] An unique request identifier that will be passed back as 30*33de042dSApple OSS Distributionspart of the io_done_result structure. 31*33de042dSApple OSS Distributions<p> 32*33de042dSApple OSS Distributions<dt> <var>mode</var> 33*33de042dSApple OSS Distributions<dd> 34*33de042dSApple OSS Distributions[in scalar] I/O mode value. Meaningful options are: 35*33de042dSApple OSS Distributions<p> 36*33de042dSApple OSS Distributions <dl> 37*33de042dSApple OSS Distributions<dt> <strong>D_NOWAIT</strong> 38*33de042dSApple OSS Distributions<dd> 39*33de042dSApple OSS DistributionsDo not wait if data is unavailable. 40*33de042dSApple OSS Distributions </dl> 41*33de042dSApple OSS Distributions<p> 42*33de042dSApple OSS Distributions<dt> <var>recnum</var> 43*33de042dSApple OSS Distributions<dd> 44*33de042dSApple OSS Distributions[in scalar] Record number to be read. 45*33de042dSApple OSS Distributions<p> 46*33de042dSApple OSS Distributions<dt> <var>bytes_wanted</var> 47*33de042dSApple OSS Distributions<dd> 48*33de042dSApple OSS Distributions[in scalar] Size of data transfer. 49*33de042dSApple OSS Distributions</dl> 50*33de042dSApple OSS Distributions<h3>DESCRIPTION</h3> 51*33de042dSApple OSS Distributions<p> 52*33de042dSApple OSS DistributionsThe <strong>device_read_async</strong> interface enqueues a read operation for a 53*33de042dSApple OSS Distributionssequence of bytes from a device object. The meaning of recnum as well 54*33de042dSApple OSS Distributionsas the specific operation performed is device dependent. 55*33de042dSApple OSS Distributions<h3>RETURN VALUES</h3> 56*33de042dSApple OSS Distributions<dl> 57*33de042dSApple OSS Distributions<strong>device_read_async</strong> returns only invalid parameter errors. 58*33de042dSApple OSS Distributions<dd> 59*33de042dSApple OSS Distributions</dl> 60*33de042dSApple OSS Distributions<h3>RELATED INFORMATION</h3> 61*33de042dSApple OSS Distributions<p> 62*33de042dSApple OSS DistributionsFunctions: 63*33de042dSApple OSS Distributions<a href="device_read_async_inband.html"><strong>device_read_async_inband</strong></a>, 64*33de042dSApple OSS Distributions<a href="DR_overwrite_async.html"><strong>device_read_overwrite_async</strong></a>, 65*33de042dSApple OSS Distributions<a href="device_write_async.html"><strong>device_write_async</strong></a>, 66*33de042dSApple OSS Distributions<a href="device_write_async_inband.html"><strong>device_write_async_inband</strong></a>, 67*33de042dSApple OSS Distributions<a href="io_done_queue_create.html"><strong>io_done_queue_create</strong></a>. 68