register_sound_dsp — register a DSP device
int register_sound_dsp (struct file_operations * fops, int dev);
Allocate a DSP device. Unit is the number of the DSP requested. Pass -1 to request the next free DSP unit. On success the allocated number is returned, on failure a negative error code is returned.
This function allocates both the audio and dsp device entries together and will always allocate them as a matching pair - eg dsp3/audio3