snd_card_file_add - add the file to the file list of the card
int snd_card_file_add (snd_card_t * card, struct file * file);
card soundcard structure file file pointer
This function adds the file to the file linked-list of the card. This linked-list is used to keep tracking the connection state, and to avoid the release of busy resources by hotplug. Returns zero or a negative error code.