device_read_async

System Trap - Read a sequence of bytes from a device object.

SYNOPSIS

kern_return_t   device_read_async
                (mach_port_t                             device,
                 mach_port_t                              queue,
                 mach_port_t                         request_id,
                 dev_mode_t                                mode,
                 recnum_t                                recnum,
                 io_buf_len_t                      bytes_wanted);

PARAMETERS

device

[in device send right] A device port to the device to be read.

queue

[in io_done queue send right] The port returned from io_done_queue_create.

request_id

[in send right] An unique request identifier that will be passed back as part of the io_done_result structure.

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.

DESCRIPTION

The device_read_async interface enqueues a read operation for a sequence of bytes from a device object. The meaning of recnum as well as the specific operation performed is device dependent.

RETURN VALUES

device_read_async returns only invalid parameter errors.

RELATED INFORMATION

Functions: device_read_async_inband, device_read_overwrite_async, device_write_async, device_write_async_inband, io_done_queue_create.