hdlc_payload
static size_t hdlc_encoded_length(const struct hdlc_payload payloads[],
const struct hdlc_payload payloads[], size_t count)
struct hdlc_payload payloads[3];
const struct hdlc_payload payload = { .len = 1, .buf = (void *)&command };
const struct hdlc_payload payload = { .len = 1, .buf = (void *)&command };