Am 12.02.2016 um 17:12 schrieb Jacek Anaszewski:
> On 02/07/2016 11:45 AM, Heiner Kallweit wrote:
>> Add support for RGB LED's. Flag LED_DEV_CAP_RGB is used to instruct
>> the core to convert HSV to RGB on output.
>>
>> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
>> ---
>> drivers/leds/led-class.c | 3 +++
>> drivers/leds/led-core.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++-
>> include/linux/leds.h | 1 +
>> 3 files changed, 51 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
>> index 18a4558..f04efd2 100644
>> --- a/drivers/leds/led-class.c
>> +++ b/drivers/leds/led-class.c
>> @@ -193,6 +193,9 @@ int led_classdev_register(struct device *parent, struct led_classdev *led_cdev)
>> char name[64];
>> int ret;
>>
>> + if (led_cdev->flags & LED_DEV_CAP_RGB)
>> + led_cdev->flags |= LED_DEV_CAP_COLOR;
>> +
>> ret = led_classdev_next_name(led_cdev->name, name, sizeof(name));
>> if (ret < 0)
>> return ret;
>> diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
>> index 798e31e..6e1adc5 100644
>> --- a/drivers/leds/led-core.c
>> +++ b/drivers/leds/led-core.c
>> @@ -45,12 +45,50 @@ static inline enum led_brightness to_hsv(struct led_classdev *cdev,
>> return ret | min(value & LED_BRIGHTNESS_MASK, cdev->max_brightness);
>> }
>>
>> +static enum led_brightness hsv_to_rgb(enum led_brightness hsv)
>> +{
>> + int h = min_t(int, (hsv >> 16) & 0xff, 251);
>> + int s = (hsv >> 8) & 0xff;
>> + int v = hsv & 0xff;
>> + int f, p, q, t, r, g, b;
>> +
>> + if (!v)
>> + return 0;
>> + if (!s)
>> + return (v << 16) + (v << 8) + v;
>> +
>> + f = DIV_ROUND_CLOSEST((h % 42) * 255, 42);
>> + p = v - DIV_ROUND_CLOSEST(s * v, 255);
>> + q = v - DIV_ROUND_CLOSEST(f * s * v, 255 * 255);
>> + t = v - DIV_ROUND_CLOSEST((255 - f) * s * v, 255 * 255);
>> +
>> + switch (h / 42) {
>> + case 0:
>> + r = v; g = t; b = p; break;
>> + case 1:
>> + r = q; g = v; b = p; break;
>> + case 2:
>> + r = p; g = v; b = t; break;
>> + case 3:
>> + r = p; g = q; b = v; break;
>> + case 4:
>> + r = t; g = p; b = v; break;
>> + case 5:
>> + r = v; g = p; b = q; break;
>> + }
>> +
>> + return (r << 16) + (g << 8) + b;
>> +}
>> +
>
> This can be moved to led-hvs-core.c. Could you also share a reference
> to the algorithm of hsv -> rgb conversion you implemented here?
>
OK, will move it. The HSV -> RGB algorithm is the one from Gonzalez / Woods
and I took it from the German wikipedia.
https://de.wikipedia.org/wiki/HSV-Farbraum#Umrechnung_HSV_in_RGB
The calculation was slightly adjusted to deal with intervals
0-255 instead of [0,1] and for hue 0-251 instead of [0, 360)
>> static int led_set_output(struct led_classdev *cdev,
>> enum led_brightness value)
>> {
>> if (!cdev->brightness_set)
>> return -ENOTSUPP;
>>
>> + if (cdev->flags & LED_DEV_CAP_RGB)
>> + value = hsv_to_rgb(value);
>> +
>> cdev->brightness_set(cdev, value);
>>
>> return 0;
>> @@ -62,6 +100,9 @@ static int led_set_output_blocking(struct led_classdev *cdev,
>> if (!cdev->brightness_set_blocking)
>> return -ENOTSUPP;
>>
>> + if (cdev->flags & LED_DEV_CAP_RGB)
>> + value = hsv_to_rgb(value);
>> +
>> return cdev->brightness_set_blocking(cdev, value);
>> }
>>
>> @@ -320,7 +361,12 @@ int led_update_brightness(struct led_classdev *led_cdev)
>> {
>> int ret = 0;
>>
>> - if (led_cdev->brightness_get) {
>> + /*
>> + * 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
>> + */
>> + if (led_cdev->brightness_get && !(led_cdev->flags & LED_DEV_CAP_RGB)) {
>> ret = led_cdev->brightness_get(led_cdev);
>> if (ret >= 0) {
>> led_cdev->brightness = ret;
>> diff --git a/include/linux/leds.h b/include/linux/leds.h
>> index 8e7db72..24eae4b 100644
>> --- a/include/linux/leds.h
>> +++ b/include/linux/leds.h
>> @@ -51,6 +51,7 @@ struct led_classdev {
>> #define LED_DEV_CAP_FLASH (1 << 23)
>> #define LED_HW_PLUGGABLE (1 << 24)
>> #define LED_DEV_CAP_COLOR (1 << 25)
>> +#define LED_DEV_CAP_RGB (1 << 26)
>
> Why two flags - COLOR and RGB? Their meaning is ambiguous.
>
There might be color LED's with HSV interface and setting the COLOR flag
but not the RGB flag would support such LED's w/o additional code.
Not sure whether such devices exist, but one additional flag might be a
small enough price for decoupling internal color handling and RGB output
conversion.
>>
>> /* Set LED brightness level
>> * Must not sleep. Use brightness_set_blocking for drivers
>>
>
>
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