On 12/01/16 20:17, Alexander Koch wrote: > Am 12.01.2016 um 20:27 schrieb Peter Meerwald-Stadler: >> On Tue, 12 Jan 2016, Alexander Koch wrote: >> >>> Enable operation of the TI OPT3001 light sensor without having an >>> interrupt line available to connect the INT pin to. >>> >>> In this operation mode, we issue a conversion request and simply wait >>> for the conversion time available as timeout value, determined from >>> integration time configuration and the worst-case time given in the data >>> sheet (sect. 6.5, table on p. 5): >>> >>> short integration time (100ms): 110ms + 3ms = 113ms >>> long integration time (800ms): 880ms + 3ms = 883ms >>> >>> This change is transparent as behaviour defaults to using the interrupt >>> method if an interrupt no. is configured via device tree. Interrupt-less >>> operation mode is performed when no valid interrupt no. is given. >> >> looks good, I'd rather use a bool for use_irq and the msecs_to_jiffies() >> call moved from the #define to the code (which is not strictly necessary >> for the patch) -- matter of taste > > Thanks - actually this is my first patch, so positive feedback much > appreciated! > > Concerning the bool for 'use_irq': I first had it that way but then > opted for the bit field of length 1 as I wasn't sure whether bool would > get optimized to the same level by the compiler. Bit fields are often less efficient as the compiler has to separate them out using shifts and masks. Also from a space point of view the data structure will be considerably padded anyway for a couple of reasons: 1) It contains u32 fields so will at least be padded to a multiple of u32. 2) Memory allocations may well be a good bit larger depending on exact sizes vs the blob levels available in the memory allocator. Basic rule of thumb - keep things simple and let the compiler do the work. So a bool is suitable here. > > I'm a bit irritated by your comment concerning the msecs_to_jiffies() > call, as my patch indeed moves this call from the #define to the code. > Did you mean it the other way round, then? Presumably ;) > My reason to move it was that I need to work with microseconds for the > IRQ-less operation mode, and jiffies are only required in one place for > the IRQ mode. Now perhaps the 'right' way to do this would be have been a precursor patch removing the define rather than lumping what is an an connected change (in many ways) in here. Overall I agree the change is worthwhile and trivial. As Peter said, it's a matter of taste! We both happen to disagree with him on this point. > > > Best regards > > lynix > -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
