ia_css_circbuf_get_offset
num = ia_css_circbuf_get_offset(cb, cb->desc->start, cb->desc->end);
max_offset = ia_css_circbuf_get_offset(cb, cb->desc->start, cb->desc->end);
chunk_offset = ia_css_circbuf_get_offset(cb,
chunk_sz = ia_css_circbuf_get_offset(cb, cb->desc->start, chunk_src) + 1;