OpenDevice

open the audio device

The OpenDevice routine grants access to the audio device. It takes an I/O audio request block (iORequest) and if it can successfully open the audio device, it loads the device pointer (io_Device) and the allocation key (ioa_AllocKey); otherwise, it returns an error (IOERR_OPENFAIL). OpenDevice increments the open count keeping the device from being expunged (Expunge). If the length (ioa_Length) is non-zero, OpenDevice tries to allocate (ADCMD_ALLOCATE) audio channels from a array of channel combination options (ioa_Data). If the allocation succeeds, the allocated channel combination is loaded into the unit field (ioa_Unit); otherwise, OpenDevice returns an error (ADIOERR_ALLOCFAILED). OpenDevice does not wait for allocation to succeed and closes (CloseDevice) the audio device if it fails. To allocate channels, OpenDevice also requires a properly initialized reply port (mn_ReplyPort) with an allocated signal bit.

unitNumber

not used

iORequest

pointer to audio request block (struct IOAudio)

ln_Pri

Allocation precedence (-128 thru 127), only necessary for allocation (non-zero length)

mn_ReplyPort- Pointer to message port for allocation, only

necessary for allocation (non-zero length)

ioa_AllocKey- Allocation key; zero to generate new key.

Otherwise, it must be set by (or copied from I/O block that is set by) previous OpenDevice function or ADCMD_ALLOCATE command (non-zero length)

ioa_Data

Pointer to channel combination options (byte array, bits 0 thru 3 correspond to channels 0 thru 3), only necessary for allocation (non-zero length)

ioa_Length

Length of the channel combination option array (0 thru 16), zero for no allocation

flags

Not used

iORequest

Pointer to audio request block (struct IOAudio)

io_Device

Pointer to device node if OpenDevice succeeds, otherwise -1

io_Unit

Bit map of successfully allocated channels (bits 0 thru 3 correspond to channels 0 thru 3)

io_Error

Error number: 0 - no error IOERR_OPENFAIL - open failed ADIOERR_ALLOCFAILED - allocation failed, no open

ioa_AllocKey

Allocation key, set to a unique number if passed a zero and OpenDevice succeeds

error

Copy of io_Error