From: "Marek Behún" <kabel@kernel.org>
To: Pavel Machek <pavel@ucw.cz>
Cc: linux-leds@vger.kernel.org, Lee Jones <lee@kernel.org>
Subject: Re: [PATCH v2 1/3] leds: turris-omnia: change max brightness from 255 to 1
Date: Sun, 16 Jul 2023 17:01:12 +0200 [thread overview]
Message-ID: <20230716170112.1f90670a@thinkpad> (raw)
In-Reply-To: <20230716091929.GA1182@bug>
On Sun, 16 Jul 2023 11:19:30 +0200
Pavel Machek <pavel@ucw.cz> wrote:
> Hi!
>
> > Using binary brightness makes more sense for this controller, because
> > internally in the MCU it works that way: the LED has a color, and a
> > state whether it is ON or OFF.
>
> So, controller can do (1, 3, 5) but not (3, 3, 3)?
>
> > The resulting brightness computation with led_mc_calc_color_components()
> > will now always result in either (0, 0, 0) or the multi_intensity value.
>
> Won't that limit you to 8 colors total?
>
> I guess I`m confused how this hw works...
Hi Pavel.
No no no. That's not how it is.
The HW exposes color control for three channels (RGB), each channel with
range 0-255 (so 16M colors). The driver exposes this via the
multi_intensity sysfs file. This is communicated to the HW via
LED_SET_COLOR I2C command.
HW also exposes setting the LED ON and OFF, via the LED_SET_STATE
I2C command.
We currently have the following sysfs files via which we set LED state
and color:
brightness
multi_intensity
Because currently the driver sets max_brightness to 255, the actual
color that is sent to HW is recalculated via
led_mc_calc_color_components(). For example with
$ echo 255 255 100 >multi_intensity
$ echo 150 >brightness
the led_mc_calc_color_components() function recalculates the channel
intensities with formula
brightness * channel_intensity / max_brightness
and so the (255, 255, 100) tuple is converted to (150, 150, 58) before
sending to HW.
What I think would make more sense is to make the two sysfs files
brightness
multi_intensity
correspond 1-to-1 with I2C commands LED_SET_STATE and LED_SET_COLOR.
This can be simply done by setting max_brightness to 1. The brightness
sysfs file then can simply control whether the LED is ON or OFF. The
multi_intensity file control the color.
I realize now that in the patch I should also make away with the call
to led_mc_calc_color_components()...
Marek
next prev parent reply other threads:[~2023-07-16 15:01 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-14 8:52 [PATCH v2 0/3] leds: turris-omnia: updates Marek Behún
2023-07-14 8:52 ` [PATCH v2 1/3] leds: turris-omnia: change max brightness from 255 to 1 Marek Behún
2023-07-16 9:19 ` Pavel Machek
2023-07-16 15:01 ` Marek Behún [this message]
2023-07-28 9:56 ` Lee Jones
2023-07-28 10:10 ` Pavel Machek
2023-08-01 9:07 ` Marek Behún
2023-07-14 8:52 ` [PATCH v2 2/3] leds: turris-omnia: initialize multi-intensity to full Marek Behún
2023-07-16 9:19 ` Pavel Machek
2023-07-14 8:52 ` [PATCH v2 3/3] leds: turris-omnia: support HW controlled mode via private trigger Marek Behún
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