Re: [PATCH v5 4/4] leds: core: add support for RGB LED's

[Jacek Anaszewski]

On 03/29/2016 10:42 PM, Heiner Kallweit wrote:
> Am 29.03.2016 um 12:05 schrieb Pavel Machek:
> > On Tue 2016-03-01 22:36:12, Heiner Kallweit wrote:
> > > Export a function to convert HSV color values to RGB.
> > > It's intended to be called by drivers for RGB LEDs.
> > >
> > > Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
> > > ---
> > > v2:
> > > - move hsv -> rgb conversion to separate file
> > > - remove flag LED_DEV_CAP_RGB
> > > v3:
> > > - call led_hsv_to_rgb only if LED_DEV_CAP_HSV is set
> > >    This is needed in cases when we have monochrome and color LEDs
> > >    as well in a system.
> > > v4:
> > > - Export led_hsv_to_rgb and let the device driver call it instead
> > >    of doing the conversion in the core
> > > v5:
> > > - don't ignore led_cdev->brightness_get silently if LED_DEV_CAP_RGB
> > >    is set but warn
> > > ---
> > >   drivers/leds/led-class.c    |  7 +++++++
> > >   drivers/leds/led-rgb-core.c | 36 ++++++++++++++++++++++++++++++++++++
> > >   include/linux/leds.h        |  8 ++++++++
> > >   3 files changed, 51 insertions(+)
> > >
> > > diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
> > > index 8a3748a..a4b144e 100644
> > > --- a/drivers/leds/led-class.c
> > > +++ b/drivers/leds/led-class.c
> > > @@ -193,6 +193,13 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
> > >   	char name[64];
> > >   	int ret;
> > >
> > > +	/*
> > > +	 * for now reading back the color is not supported as multiple
> > > +	 * HSV -> RGB -> HSV conversions may distort the color due to
> > > +	 * rounding issues in the conversion algorithm
> > > +	 */
> > > +	WARN_ON(led_cdev->flags & LED_DEV_CAP_RGB && led_cdev->brightness_get);
> > > +
> >
> > Backtrace is useless here, you may want to add some ()s and you don't
> > really want user to be causing messages in syslog this easily.
> I agree that the backtrace doesn't provide a benefit here.

I requested it to provide a verbose notification for a LED RGB class
driver developer, in case they try to implement a brightness_get
op, which would be harmful in case of HSV interface for RGB LEDs.

> However I don't see how a user could create syslog entries.
> The warn condition can be true only for drivers implementing the RGB extension
> in a not supported way (by setting flag LED_DEV_CAP_RGB and implementing
> brightness_get).
>
> 									Pavel
> >


--
Best regards,
Jacek Anaszewski