R_I_S
bd_status = R_E_S | R_I_S;
bd_status = R_E_S | R_I_S | R_W_S;
bd->status = cpu_to_be16((bd_status & R_W_S) | R_E_S | R_I_S);
bd_status = R_E_S | R_I_S;
bd_status = R_E_S | R_I_S | R_W_S;