Re: [PATCH v3 6/9] leds: multicolor: Introduce a multicolor class definition
From: Jacek Anaszewski
Date: Thu Jun 20 2019 - 17:42:31 EST
Dan,
On 6/20/19 10:06 PM, Dan Murphy wrote:
Jacek
Thanks for the review
You're welcome.
On 6/20/19 11:10 AM, Jacek Anaszewski wrote:
Hi Dan,
Thank you for the v5.
I will confine myself to commenting only some parts since
the rest will undergo rework due to removal of sync API.
On 5/23/19 9:08 PM, Dan Murphy wrote:
Introduce a multicolor class that groups colored LEDs
within a LED node.
The framework allows for dynamically setting individual LEDs
or setting brightness levels of LEDs and updating them virtually
simultaneously.
Signed-off-by: Dan Murphy <dmurphy@xxxxxx>
---
 drivers/leds/Kconfig | 10 +
 drivers/leds/Makefile | 1 +
 drivers/leds/led-class-multicolor.c | 421 +++++++++++++++++++++++++++
 include/linux/led-class-multicolor.h | 95 ++++++
 4 files changed, 527 insertions(+)
 create mode 100644 drivers/leds/led-class-multicolor.c
 create mode 100644 include/linux/led-class-multicolor.h
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 0414adebb177..0696a13c9527 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -29,6 +29,16 @@ config LEDS_CLASS_FLASH
ÂÂÂÂÂÂÂ for the flash related features of a LED device. It can be built
ÂÂÂÂÂÂÂ as a module.
 +config LEDS_CLASS_MULTI_COLOR
+ÂÂÂ tristate "LED Mulit Color LED Class Support"
+ÂÂÂ depends on LEDS_CLASS
+ÂÂÂ help
+ÂÂÂÂÂ This option enables the multicolor LED sysfs class in
/sys/class/leds.
+ÂÂÂÂÂ It wraps LED Class and adds multicolor LED specific sysfs
attributes
+ÂÂÂÂÂ and kernel internal API to it. You'll need this to provide
support
+ÂÂÂÂÂ for multicolor LEDs that are grouped together. This class is not
+ intended for single color LEDs. It can be built as a module.
extra whitespace:
s/ It can/It can/
Ack
[...]
+
+static int multicolor_set_brightness(struct led_classdev *led_cdev,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ enum led_brightness brightness)
+{
+ÂÂÂ struct led_classdev_mc *mcled_cdev = lcdev_to_mccdev(led_cdev);
+ÂÂÂ struct led_classdev_mc_data *data = mcled_cdev->data;
+ÂÂÂ struct led_multicolor_ops *ops = mcled_cdev->ops;
+ÂÂÂ struct led_classdev_mc_priv *priv;
+ÂÂÂ unsigned long state = brightness;
+ÂÂÂ int adj_value;
+ÂÂÂ ssize_t ret = -EINVAL;
+
+ÂÂÂ mutex_lock(&led_cdev->led_access);
+
+ÂÂÂ if (ops->set_module_brightness) {
+ÂÂÂÂÂÂÂ ret = ops->set_module_brightness(mcled_cdev, state);
+ÂÂÂÂÂÂÂ goto unlock;
+ÂÂÂ }
+
+ÂÂÂ list_for_each_entry(priv, &data->color_list, list) {
+ÂÂÂÂÂÂÂ if (state && priv->brightness && priv->max_brightness) {
+ÂÂÂÂÂÂÂÂÂÂÂ adj_value = state * ((priv->brightness * 100) /
priv->max_brightness);
+ÂÂÂÂÂÂÂÂÂÂÂ adj_value = adj_value / 100;
Why the multiplication an then division by 100? And priv->max_brightness
stays unaltered? This changes the proportions. My python script works
just fine without those.
Because the kernel does not do floating point math and the calculation
is using the ratio
between the intensity and max_intensity and multiplying against the
requested brightness.
priv->intensity = 100 (This is the current intensity of the color LED)
priv->max_intensity = 255
state = 80 (This is the requested cluster brightness)
100/255 = 0.392 which is 0.
0 * 80 = 0 this is not what the value should be
But with the multiplier.
10000/255 = 39.2 which is 39 which means that the intensity is only 39%
of the
max_intensity.
39 * 80 = 3120Â So to preserve the 39% from the 80 we multiply the
percentage * requested cluster brightness
3120 / 100 = 31 then we normalize back
I am not sure how your script is working without the multiplier.
Try to remove brackets around division operation.
Then first we are multiplying and only after that dividing.
$ echo "80 * 100 / 255" | bc
31
+ÂÂÂÂÂÂÂ } else
+ÂÂÂÂÂÂÂÂÂÂÂ adj_value = LED_OFF;
+
+ÂÂÂÂÂÂÂ ret = ops->set_color_brightness(priv->mcled_cdev,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ priv->color_id,ÂÂÂ adj_value);
+ÂÂÂÂÂÂÂ if (ret < 0)
+ÂÂÂÂÂÂÂÂÂÂÂ goto unlock;
+ÂÂÂ }
+
+unlock:
+ÂÂÂ mutex_unlock(&led_cdev->led_access);
+ÂÂÂ return ret;
+}
[...]
+int led_classdev_multicolor_register_ext(struct device *parent,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct led_classdev_mc *mcled_cdev,
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ struct led_init_data *init_data)
+{
+ÂÂÂ struct led_classdev *led_cdev;
+ÂÂÂ struct led_multicolor_ops *ops;
+ÂÂÂ struct led_classdev_mc_data *data;
+ÂÂÂ int ret;
+ÂÂÂ int i;
+
+ÂÂÂ if (!mcled_cdev)
+ÂÂÂÂÂÂÂ return -EINVAL;
+
+ÂÂÂ ops = mcled_cdev->ops;
+ÂÂÂ if (!ops || !ops->set_color_brightness)
+ÂÂÂÂÂÂÂ return -EINVAL;
+
+ÂÂÂ data = kzalloc(sizeof(*data), GFP_KERNEL);
+ÂÂÂ if (!data)
+ÂÂÂÂÂÂÂ return -ENOMEM;
+
+ÂÂÂ mcled_cdev->data = data;
+ÂÂÂ led_cdev = &mcled_cdev->led_cdev;
+
+ÂÂÂ if (led_cdev->brightness_set_blocking)
+ÂÂÂÂÂÂÂ led_cdev->brightness_set_blocking = multicolor_set_brightness;
This is weird. In leds-lp50xx.c you don't initialize
brightness_set_blocking and this still works?
I will have to look. I don't believe I retested this on lp50xx only the
lp55xx code.
I believe this is kind of omission.
And it is not reasonable to just override driver supplied op with
generic one just like that.
I propose to initialize brightness_set or brightness_set_blocking
op as we used to do it for monochrome LEDs. Those function(s) on
driver side will either use device's hardware support for setting
color lightness, or will call a generic function provided by
LED multi color class for calculating intensities of all colors
it comprises in the cluster.
I know this is different to what we've discussed on IRC, but now
it looks for me the most reasonable way to go.
So you want the device driver to handle the brightness request and call
into the framework for
calculating the color intensities?
Exactly.
That would work as well and solves a problem of HW supported brightness
control like the LP50xx.
The LP50xx would not need to call into the function for calculated
intensities.
True.
--
Best regards,
Jacek Anaszewski