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    SubjectRe: [PATCH 01/13] input: touchscreen: use polling mode in 88pm860x
    On Sat, 16 Apr 2011 20:46:20 +0800, Haojian Zhuang said:
    > Measuring point on touchscreen with IRQ mode can only monitor pen-down
    > event. If finger is moving on touchscreen, it can't be monitored by
    > IRQ pen-down event. So switch to polling mode after pen-down event.

    > drivers/input/touchscreen/88pm860x-ts.c | 79 ++++++++++++++++++++++++------

    > +/*
    > + * While 32KHz hardware timer is used for scheduler, we always assign HZ
    > + * to 128. It means that 1 tick costs 7.8msec.
    > + */
    > +#define MEASURE_INTERVAL_MS (7)

    Is it guaranteed that this hardware part will only ever be used on systems
    where this is true? How big a bug would it be if somebody tried to glue this
    touchscreen into some random embedded-ARM where HZ was something else, and
    should this be computed as a function of HZ instead of hardcoding 7?

    It *looks* like the intent of the schedule_delayed_work() call is "let's run
    this once a tick when we're awake *anyhow*" - but looking at the code, I can't
    convince myself a rounding error in computing 'interval' won't schedule 1ms
    before or after the next tick would have been. Isn't there a better API with
    slack timers or something that would do a better "next tick" job?

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