On Sat, 4 Jul 2020 14:59:00 +0200 Pavel Machek <pavel@xxxxxx> wrote: > Hi! > > > Some criticism to this approach to HW triggers: > > - every hw trigger for each LED has to be registered via current > > trigger API. This will grow code size and memory footprint once > > this API is widely used > > - one HW trigger can only master one LED device (via private_led > > member). So if I have, for example an ethernet switch with 8 > > ports, and each port has 2 LEDs, and each LED has 10 possible HW > > triggering mechanisms, with your proposed API one would need to > > register 8*2*10 = 160 triggers > > Well, code is simple, and so far I have seen 2 HW triggering > mechanisms, not 10. Maybe we should have a function to regiter a hw > trigger for a LED, so that internal implementation can be changed > more easily. > > Ondrej: You already have code using this, right? Can we get an > example? > > > I too have been thinking about an API for HW LED triggers, and I > > tinkered with it a little. Some time ago I sent some emails, with > > subjects: > > "RFC: LED hw triggering API" > > "about my trigger-sources work" > > Perhaps it is time to send them one more time, so Ondrej can say if it > works for him/looks okay for him? > > > My current thoughts about how HW LED triggers could work nicely is > > as such: > > - these members (maybe with different names) shall be added to > > struct led_classdev: > > available_hw_triggers() > > - shall return a NULL terminated list of HW trigger names > > available for this LED > > set_hw_trigger() > > - sets HW trigger for this LED. The LED triggering API shall > > call this method after previous LED trigger is unset. If > > called with NULL parameter, unsets HW trigger > > current_hw_trigger > > - name of the currently set HW LED trigger for this LED > > - the driver registering the LED cdev informs abouth the LED being > > capable of HW triggering - members available_hw_triggers and > > set_hw_trigger must be set > > - SW LED trigger and HW LED trigger are mutualy exclusive on one > > LED > > - the trigger file in sysfs (/sys/class/leds/LED/trigger) shall > > first list the available SW triggers, and then available hw > > triggers for this LED, prefixed with "hw:" > > When written, if the written trigger name starts with "hw:", > > instead of setting SW trigger, a HW trigger is set via > > set_hw_trigger() method > > This does not sound bad, either. > > Best regards, > Pavel Hi Pavel I shall try to implement this and send a proposal within 2 weeks. Marek
