Hi! Jacek, could we get you to comment here? I'd prefer "hardware" trigger... > >>That assumes that breathing is the default setting on all hardware > >>and again I don't see why not to export this functionality to > > > >Save the status on boot, then restore it on rmmod/reboot/poweroff? :-). > > Which works until the system freezes one time. I believe that > if we are going to do a LED driver for the charging LED on these > devices, we MUST offer a way to put it back in its original > state, even if the state is foo-barred at bootup. > > >>userspace. Just because something does not fit in the existing > >>API is IMHO not a good reason to not expose it to userspace. > >> > >>I suggest that we deal with this special case by adding 3 custom > >>sysfs attributes: > >> > >>1) "mode" which when read, prints, e.g. : > >>manual [on-when-charging] > > > >While this allows _user on console_ to control everything using echo, > >it is not suitable for applications trying to control LEDs. > > > >As there's nothing special about the case here, I believe we should > >have generic solution here. > > > >My preffered solution would be "hardware" trigger that leaves the LED > >in hardware control. > > As you explained in the parts which I snipped, there are many > devices which have a similar choice for a LED being under hw or > user control. I can see how this looks like a trigger and how we > could use the trigger API for this. > > I believe though, that if we implement a "virtual" (for lack of > a better word) trigger for this, that this should be done in the > LED core. I can envision this working like this: Agreed about the LED core. > 1) Add a: > > hw_control_set(struct led_classdev *led_cdev, bool enable_hw_control); > > Callback to struct led_classdev which when implemented by a driver > like the current PMIC LED controller would do what it says. > > 2) Have the core create and register a virtual hardware trigger the > first time a LED cdev which has this callback gets registered. > > When configured as the trigger for this LED device this trigger calls > hw_control_set(cdev, true) and when unregistered calls > hw_control_set(cdev, false) > > Taking a quick look at the trigger code, a problem with this is > that normally any trigger can work with any led device, so this > "hardware" trigger will show up in the list of possible > triggers for each device. > > This problem can be solved by making the activate method for the > hardware trigger check the classdev has a hw_control_set callback > and if not return -EINVAL, or maybe -ENXIO but still this is somewhat > inconsistent with other triggers, which AFAIK work with any LED. I guess other option is to modify core so that it does not list "hardware" trigger for leds that don't support it. > >Alternatively I could imagine "hardware" sysfs attribute, containing > >0/1, with 0==software controlled, 1==hardware controlled. > > Hmm, maybe call it "hardware_controlled" instead ? Otherwise this > would work for me and I would personally prefer this solution. This > could even be done in the LED core using the hw_control_set callback > I proposed, to make sure it is handled consistently between devices. This should be in LED core, yes. > >The rest of attributes would have to be Cove-specific, yes (but still > >should fit with the rest of LED subsystem). > > Right, I see that the triggers attribute already uses the fmt where > on "cat" all options are listed and the current active one has [] around it, > so I think the pattern and frequency attributes I proposed should work > well, although thinking more about this I believe the freq. attribute should > be called pattern_freq to make clear it applies to blinking / breathing > set through the pattern attribute. Take a look at blinking trigger. It can already do hardware acceleration, but uses different format than what you proposed. Best regards, Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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