1<h2>device_read_overwrite</h2> 2<hr> 3<p><strong>System Trap</strong> -- Read a sequence of bytes from a specific device into my address space. 4<h3>SYNOPSIS</h3> 5<pre> 6 7<strong>kern_return_t device_read_overwrite</strong> 8 <strong>(mach_port_t</strong> <var>device</var>, 9 <strong>dev_mode_t</strong> <var>mode</var>, 10 <strong>recnum_t</strong> <var>recnum</var>, 11 <strong>io_buf_len_t</strong> <var>bytes_wanted</var>, 12 <strong>io_buf_pointer_t</strong> <var>data</var>, 13 <strong>mach_msg_type_number_t</strong> <var>data_count</var><strong>);</strong> 14 15 16 17<strong>kern_return_t device_read_overwrite_request</strong> 18 <strong>(mach_port_t</strong> <var>device</var>, 19 <strong>mach_port_t</strong> <var>reply_port</var>, 20 <strong>dev_mode_t</strong> <var>mode</var>, 21 <strong>recnum_t</strong> <var>recnum</var>, 22 <strong>io_buf_len_t</strong> <var>bytes_wanted</var>, 23 <strong>io_buf_pointer_t</strong> <var>data</var><strong>);</strong> 24 25 26 27<strong>kern_return_t ds_device_read_reply_overwrite</strong> 28 <strong>(mach_port_t</strong> <var>reply_port</var>, 29 <strong>kern_return_t</strong> <var>return_code</var>, 30 <strong>io_buf_len_t</strong> <var>data_count</var><strong>);</strong> 31</pre> 32<h3>PARAMETERS</h3> 33<dl> 34<p> 35<dt> <var>device</var> 36<dd> 37[in device send right] 38A device port to the device to be read. 39<p> 40<dt> <var>reply_port</var> 41<dd> 42[in reply receive (to be converted to send-once) right] 43The port to 44which the reply message is to be sent. 45<p> 46<dt> <var>mode</var> 47<dd> 48[in scalar] 49I/O mode value. Meaningful options are: 50<dl> 51<p> 52<dt> <strong>D_NOWAIT</strong> 53<dd> 54Do not wait if data is unavailable. 55</dl> 56<p> 57<dt> <var>recnum</var> 58<dd> 59[in scalar] 60Record number to be read. 61<p> 62<dt> <var>bytes_wanted</var> 63<dd> 64[in scalar] 65Size of data transfer. 66<p> 67<dt> <var>return_code</var> 68<dd> 69[in scalar] 70The return status code from the read. 71<p> 72<dt> <var>data</var> 73<dd> 74[pointer to in array of bytes] 75Data buffer to be overwritten. 76<p> 77<dt> <var>data_count</var> 78<dd> 79[out scalar, in for asynchronous form] 80Number of returned data bytes. 81</dl> 82<h3>DESCRIPTION</h3> 83<p> 84The <strong>device_read_overwrite</strong> system trap reads a sequence 85of bytes from a 86device object directly into the caller's address space. The 87meaning of <var>recnum</var> as 88well as the specific operation performed is device dependent. 89<h3>NOTES</h3> 90<p> 91The <strong>device_read_overwrite_request</strong> and <strong>device_read_reply_overwrite</strong> 92calls may be removed from the interface in favor of new asynchronous support. 93<h3>RETURN VALUES</h3> 94<p> 95Only generic errors apply. 96<h3>RELATED INFORMATION</h3> 97<p> 98Functions: 99<a href="device_read.html"><strong>device_read</strong></a>, 100<a href="device_read_inband.html"><strong>device_read_inband</strong></a>, 101<a href="device_reply_server.html"><strong>device_reply_server</strong></a>. 102