From: Pavel Machek <pavel@ucw.cz>
To: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>,
Jacek Anaszewski <j.anaszewski@samsung.com>,
Greg KH <greg@kroah.com>,
linux-leds@vger.kernel.org,
Benjamin Tissoires <benjamin.tissoires@redhat.com>,
linux-kernel@vger.kernel.org, linux-usb@vger.kernel.org,
pali.rohar@gmail.com, sre@kernel.org, khilman@kernel.org,
aaro.koskinen@iki.fi, ivo.g.dimitrov.75@gmail.com,
Patrik Bachan <patrikbachan@gmail.com>,
serge@hallyn.com
Subject: Re: [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's
Date: Wed, 6 Apr 2016 11:12:28 +0200 [thread overview]
Message-ID: <20160406091228.GC10196@amd> (raw)
In-Reply-To: <5704236D.5080805@gmail.com>
Hi!
> > We would probably need additional op in the LED core : color_set.
> >
> > Having the color set to nonzero value would signify the the three LED
> > class devices are in sync and that setting a trigger on any of them
> > applies to the remaining two ones. It would have to be considered
> > whether existing triggers could be made compatible with synchronized
> > RGB LED class devices.
> >
> > I'm curious what do you think about the idea.
> >
> > Pavel, Heiner, others?
> >
> Exposing "coupled LED devices" as separate LED devices most likely is ok
> when accessed from user space as the name of the led_classdev's indicates
> that they belong together.
> But how about a trigger wanting to set a RGB LED to a specific color?
> (That's not available yet but one possible use case for RGB LED's)
> A trigger is bound to a led_classdev currently. In addition we'd need
> to introduce some kind of super_led_classdev having links to the respective
> R/G/B led_classdev's (+ trigger functions dealing with this super_led_classdev).
>
> These changes / extensions are not needed if a RGB LED is exposed as one
> led_classdev, just with flag LED_DEV_CAP_RGB set.
> OK, we'd still have to change the sysfs interface as obviously setting
> hue/sat/brightness via one "brightness" attribute is not acceptable.
> However this constraint might not affect the kernel-internal trigger API
> (usage of parameter brightness in led_trigger_event).
Your proposal would break existing hardware. We already have RGB LEDs
exposed as three LEDs. It is too late to change interface there.
> I see Pavel's point that there might be different types of multi-color LED's.
> At least we have:
> - multi-color LED's where each single LED is visible even if all are switched on
> - multi-color LED's like RGB LED's where you usually just see a
> uniform color
Well, I suggest we ignore that distinction. Yes, I can see different
colors coming from different directions, but the LED was clearly
designed to look like single light.
> Last but not least regarding the patterns:
> Something like proposed by Pavel is e.g. (partially) supported by the blink(1)
> firmware. That would be an example of such a "hardware-accelerated" pattern.
>
> As I see it the current blinking support then would be one special case of a pattern.
> As a consequence once having pattern support we might be able to switch users of blinking
> to pattern and remove the blinking support.
No, you can't remove existing blinking support, due to backwards
compatibility reasons.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
next prev parent reply other threads:[~2016-04-06 9:12 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-01 21:26 [PATCH v5 1/4] leds: core: add generic support for RGB Color LED's Heiner Kallweit
2016-03-04 9:04 ` Jacek Anaszewski
2016-03-29 10:02 ` Pavel Machek
2016-03-29 20:38 ` Heiner Kallweit
2016-03-29 21:43 ` Pavel Machek
2016-03-29 22:03 ` Pavel Machek
2016-03-30 5:58 ` Heiner Kallweit
2016-04-01 12:52 ` Pavel Machek
2016-03-30 8:07 ` Jacek Anaszewski
2016-03-30 13:03 ` Pavel Machek
2016-03-30 13:59 ` Heiner Kallweit
2016-03-31 8:17 ` Jacek Anaszewski
2016-04-01 12:55 ` Pavel Machek
2016-04-01 13:28 ` Jacek Anaszewski
2016-04-01 14:07 ` Pavel Machek
2016-04-01 14:27 ` Jacek Anaszewski
2016-04-01 15:03 ` Pavel Machek
2016-04-01 12:53 ` Pavel Machek
2016-03-30 7:57 ` Jacek Anaszewski
2016-04-01 13:57 ` Pavel Machek
2016-04-01 18:56 ` Jacek Anaszewski
2016-04-01 21:18 ` Pavel Machek
2016-04-04 21:34 ` Jacek Anaszewski
2016-04-05 9:01 ` Pavel Machek
2016-04-05 19:45 ` Jacek Anaszewski
2016-04-05 20:43 ` Heiner Kallweit
2016-04-05 22:15 ` Jacek Anaszewski
2016-04-06 9:16 ` Pavel Machek
2016-04-06 9:12 ` Pavel Machek [this message]
2016-04-06 8:52 ` Pavel Machek
2016-04-06 9:53 ` Jacek Anaszewski
2016-04-07 20:45 ` Pavel Machek
2016-04-08 18:47 ` Jacek Anaszewski
2016-04-09 16:01 ` Pavel Machek
2016-04-12 7:13 ` Jacek Anaszewski
2016-04-15 11:53 ` Pavel Machek
2016-04-18 9:12 ` Jacek Anaszewski
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