osfmk/man/device_read.html
Function - Read a sequence of bytes from a specific device.
**#include<device/device.h>**** kern\_return\_t device\_read****(device\_t**device, **mach\_port\_t** reply\_port, **dev\_mode\_t** mode, **recnum\_t** recnum, **io\_buf\_len\_t** bytes\_wanted, **io\_buf\_ptr\_t** io\_buf\_ptr\_t, **mach\_msg\_type\_number\_t** mach\_msg\_type\_number\_t**);****#include<device/device\_request.h> ****kern\_return\_t device\_read\_request**** (mach\_port\_t **device,** mach\_port\_t **reply\_port,** dev\_mode\_t **mode,** recnum\_t **recnum,** io\_buf\_len\_t **bytes\_wanted** ); ****kern\_return\_t ds\_device\_read\_reply**** (mach\_port\_t **reply\_port,** kern\_return\_t **return\_code,** io\_buf\_ptr\_t **data,** mach\_msg\_type\_number\_t **data\_count** );**
device[in device send right] A device port to the device to be read.
reply_port[in reply receive (to be converted to send-once) right] The port to which the reply message is to be sent.
mode[in scalar] I/O mode value. Meaningful options are:
D_NOWAIT Do not wait if data is unavailable.
recnum[in scalar] Record number to be read.
bytes_wanted[in scalar] Size of data transfer.
return_code[in scalar] The return status code from the read.
data[out pointer to dynamic array of bytes, in for asynchronous form] Returned data bytes.
data_count[out scalar, in for asynchronous form] Number of returned data bytes.
The device_read function reads a sequence of bytes from a device object. The meaning of recnum as well as the specific operation performed is device dependent.
Only generic errors apply.
Functions: device_read_inband, device_read_overwrite, device_reply_server.