leds: multicolor: Use rounded division when calculating color components

[ Upstream commit 065d099f1be58187e6629273c50b948a02b7e1bf ]

Given channel intensity, LED brightness and max LED brightness, the
multicolor LED framework helper led_mc_calc_color_components() computes
the color channel brightness as

    chan_brightness = brightness * chan_intensity / max_brightness

Consider the situation when (brightness, intensity, max_brightness) is
for example (16, 15, 255), then chan_brightness is computed to 0
although the fractional divison would give 0.94, which should be rounded
to 1.

Use DIV_ROUND_CLOSEST here for the division to give more realistic
component computation:

    chan_brightness = DIV_ROUND_CLOSEST(brightness * chan_intensity,
                                        max_brightness)

Fixes: 55d5d3b46b08 ("leds: multicolor: Introduce a multicolor class definition")
Signed-off-by: Marek Behún <kabel@kernel.org>
Link: https://lore.kernel.org/r/20230801124931.8661-1-kabel@kernel.org
Signed-off-by: Lee Jones <lee@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/leds/led-class-multicolor.c b/drivers/leds/led-class-multicolor.c
index e317408..ec62a48 100644 (file)
--- a/drivers/leds/led-class-multicolor.c
+++ b/drivers/leds/led-class-multicolor.c
@@ -6,6 +6,7 @@
 #include <linux/device.h>
 #include <linux/init.h>
 #include <linux/led-class-multicolor.h>
+#include <linux/math.h>
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/uaccess.h>
@@ -19,9 +20,10 @@ int led_mc_calc_color_components(struct led_classdev_mc *mcled_cdev,
        int i;
 
        for (i = 0; i < mcled_cdev->num_colors; i++)
-               mcled_cdev->subled_info[i].brightness = brightness *
-                                       mcled_cdev->subled_info[i].intensity /
-                                       led_cdev->max_brightness;
+               mcled_cdev->subled_info[i].brightness =
+                       DIV_ROUND_CLOSEST(brightness *
+                                         mcled_cdev->subled_info[i].intensity,
+                                         led_cdev->max_brightness);
 
        return 0;
 }