drivers: led_strip: ws2812_gpio: fix overwriting in loop

Due to the alias of ptr on pixels, one iterates over the same area
one reads from to set values. Therefore, if the strip is not 'RGB' but
GBR, one would overwrite the pixels 'r' value with the 'g' value in the
first loop, leading to a wrong read afterwards.

By writing to a temporary variable, we have a clean, unmodified copy
of the original values.

Additionally, this removes the dependency on 'LED_STRIP_RGB_SCRATCH',
as the scratch part (that masked most error cases) is not necessary
anymore.

Signed-off-by: Stefan Kraus <[email protected]>

Author: Alicipy

drivers/led_strip/Kconfig.ws2812

@@ -46,7 +46,6 @@ config WS2812_STRIP_GPIO
 	default y
 	depends on DT_HAS_WORLDSEMI_WS2812_GPIO_ENABLED
 	depends on (SOC_SERIES_NRF91X || SOC_SERIES_NRF51X || SOC_SERIES_NRF52X || SOC_SERIES_NRF53X)
-	select LED_STRIP_RGB_SCRATCH
 	help
 	  Enable driver for WS2812 (and compatibles) LED strip directly
 	  controlling with GPIO. The GPIO driver does bit-banging with inline

drivers/led_strip/ws2812_gpio.c

@@ -140,6 +140,7 @@ static int ws2812_gpio_update_rgb(const struct device *dev,
 	/* Convert from RGB to on-wire format (e.g. GRB, GRBW, RGB, etc) */
 	for (i = 0; i < num_pixels; i++) {
 		uint8_t j;
+		const struct led_rgb current_pixel = pixels[i];
 
 		for (j = 0; j < config->num_colors; j++) {
 			switch (config->color_mapping[j]) {
@@ -148,13 +149,13 @@ static int ws2812_gpio_update_rgb(const struct device *dev,
 				*ptr++ = 0;
 				break;
 			case LED_COLOR_ID_RED:
-				*ptr++ = pixels[i].r;
+				*ptr++ = current_pixel.r;
 				break;
 			case LED_COLOR_ID_GREEN:
-				*ptr++ = pixels[i].g;
+				*ptr++ = current_pixel.g;
 				break;
 			case LED_COLOR_ID_BLUE:
-				*ptr++ = pixels[i].b;
+				*ptr++ = current_pixel.b;
 				break;
 			default:
 				return -EINVAL;