137             return None;  in inner_try_read()
144             return None;  in inner_try_read()
149                 irq_guard: None,  in inner_try_read()
161                 None => spin_loop(),  in read()
175                 None => spin_loop(),  in read_irqsave()
187             return None;  in try_read_irqsave()
249                 irq_guard: None,  in inner_try_write()
252             return None;  in inner_try_write()
263                 None => spin_loop(),  in write()
279                 None => spin_loop(),  in write_irqsave()
318                 irq_guard: None,  in inner_try_upgradeable_read()
321             return None;  in inner_try_upgradeable_read()
332                 None => spin_loop(),  in upgradeable_read()
347                 None => spin_loop(),  in upgradeable_read_irqsave()