UAC_DT_AC_HEADER_SIZE
.bLength = UAC_DT_AC_HEADER_SIZE(1),
.wTotalLength = cpu_to_le16(UAC_DT_AC_HEADER_SIZE(1)),
ac_header_desc_size = UAC_DT_AC_HEADER_SIZE(num_ifaces);
#define UAC_DT_AC_HEADER_LENGTH UAC_DT_AC_HEADER_SIZE(F_AUDIO_NUM_INTERFACES)