Messages in this thread | | | Date | Thu, 30 Apr 2015 20:11:41 +0300 | From | Stas Sergeev <> | Subject | Re: [PATCH v2 0/3] leds: blink resolution improvements |
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28.04.2015 15:58, Jacek Anaszewski пишет: >>> I tried it with Samsung M0 board and >>> my leds-aat1290 driver. It didn't work well. And for small delay >>> intervals it will not have a chance to work reliably with all drivers, >>> especially the ones which use mutex in their brightness_set op, >>> since mutex can sleep. >> OK, I can remove the nsec resolution. > > usec also didn't work, please look at my use case and warning: > > echo "timer" > trigger > echo 1 > delay_on > echo 1 > delay_off > echo usec > delay_unit > [ 178.584433] hrtimer: interrupt took 300747 ns > > Only some time later I realized that for AAT1290 brightness is set > through ASCwire pulse protocol, which takes few ms. > > Please note that with this approach users would have to wonder why > they are getting the warnings and why they can't get their LEDs to work > with given settings. I've now found that the drivers itself use a work queue when needed. And some drivers, like leds_gpio, even do this: --- if (led_dat->can_sleep) { led_dat->new_level = level; schedule_work(&led_dat->work); } else { set_brightness_now(); } --- So it seems the problem is already solved on the per-driver basis. I don't have leds-aat1290 driver, it is probably not in the kernel. It is likely forgetting to use the work-queue the way all other drivers do. So I think my patch is good for the in-kernel drivers.
There is also a led_cdev->set_brightness_work, and it looks unused. I could use it for my patch, but for what, if the drivers already use the work queue when needed?
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