snd_rawmidi_transmit - copy from the buffer to the device
int snd_rawmidi_transmit (snd_rawmidi_substream_t * substream, unsigned char * buffer, int count);
substream the rawmidi substream buffer the buffer pointer count the data size to transfer
Copies data from the buffer to the device and advances the pointer. Returns the copied size if successful, or a negative error code on failure.