On Fri, Dec 3, 2010 at 6:42 AM, Mark Brown <broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > > The sysfs interface offered by polldev is *mostly* doing the same thing True, except that there is still no synchronization of the polling events between the driver and application. For example, if the polling interval is once per second then the sample ultimately delivered to applications could be almost one second old--- even if the application reads from the evdev interface once a second as well. The callback can be used to reduce the delay between sample generation and event delivery. It can also increase system load, but reduces phase error in situations where that is desirable. I don't expect that many drivers will use the callback, but for the ones that do it will be very useful. > A callback on read seems like it's a bit limited as it's more work for > the application (handling the latency introduced by waking up from your > delay and doing the read is faff) and requires polling in the hardware > too. Right. But if the hardware works that way anyway, then the alternatives seem to boil down to either unsynchronized polling, or samples-on-demand. Some applications e.g. mine, really want the latter. b.g. -- Bill Gatliff bgat@xxxxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
