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Message-ID: <20251230003250.1197744-5-professorjonny98@gmail.com> Date: Tue, 30 Dec 2025 13:32:41 +1300 From: Jonathan Brophy <professorjonny98@...il.com> To: lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>, Andriy Shevencho <andriy.shevchenko@...ux.intel.com>, Jonathan Brophy <professor_jonny@...mail.com>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Radoslav Tsvetkov <rtsvetkov@...dotech.eu> Cc: devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-leds@...r.kernel.org Subject: [PATCH v4 4/7] ABI: Add sysfs documentation for leds-group-virtualcolor From: Jonathan Brophy <professor_jonny@...mail.com> Document the sysfs ABI for the virtual LED group driver, including: - mc/multi_intensity: Per-channel intensity control (0-255) - mc/multi_index: Channel-to-color-ID mapping (read-only) - mc/multi_multipliers: Per-channel scale factors (read-only) - brightness: Master brightness control with arbitration trigger - max_brightness: Maximum brightness value (mode-dependent) Channel ordering is deterministic, sorted by ascending LED_COLOR_ID value. For RGBW LEDs, white (ID=0) appears first, followed by RGB. The multi_intensity attribute is rate-limited to 100 updates/second per virtual LED by default, with counters visible in debugfs when CONFIG_DEBUG_FS is enabled. Co-developed-by: Radoslav Tsvetkov <rtsvetkov@...dotech.eu> Signed-off-by: Radoslav Tsvetkov <rtsvetkov@...dotech.eu> Signed-off-by: Jonathan Brophy <professor_jonny@...mail.com> --- .../sysfs-class-led-driver-virtualcolor | 168 ++++++++++++++++++ 1 file changed, 168 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-led-driver-virtualcolor diff --git a/Documentation/ABI/testing/sysfs-class-led-driver-virtualcolor b/Documentation/ABI/testing/sysfs-class-led-driver-virtualcolor new file mode 100644 index 000000000000..704f2e5f2af7 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-led-driver-virtualcolor @@ -0,0 +1,168 @@ +What: /sys/class/leds/<led>/mc/multi_intensity +Date: December 2024 +KernelVersion: 6.x +Contact: Jonathan Brophy <professor_jonny@...mail.com> +Description: + Control the intensity values for each color channel in a + virtual multicolor LED. + + Reading returns space-separated intensity values (0-255) for + each configured color channel. Channel order is deterministic, + sorted by ascending LED_COLOR_ID value. Use multi_index to + determine which color corresponds to each position. + + Writing accepts space-separated intensity values to set the + per-channel intensities. The number of values must match the + number of channels. Values must be ordered to match multi_index. + + Channel ordering examples: + RGB LED (no white): + multi_index shows "1 2 3" + Order is: red (ID 1), green (ID 2), blue (ID 3) + + RGBW LED (with white): + multi_index shows "0 1 2 3" + Order is: white (ID 0), red (ID 1), green (ID 2), blue (ID 3) + Note: White comes FIRST because LED_COLOR_ID_WHITE = 0 + + Example (RGB LED with 3 channels): + $ cat /sys/class/leds/myled/mc/multi_index + 1 2 3 + $ cat /sys/class/leds/myled/mc/multi_intensity + 255 128 0 + $ echo "128 64 200" > /sys/class/leds/myled/mc/multi_intensity + + Note: In standard mode (led-mode = "standard"), intensity + changes are rejected with -EPERM and the color is fixed by the + channel multipliers defined in the device tree. In multicolor + mode (led-mode = "multicolor", default), intensity can be + freely modified. + + This attribute is rate-limited to prevent system overload + (default: 100 updates/second per virtual LED). Excessive + updates will be silently dropped with incremented rate limit + counters (visible in debugfs when CONFIG_DEBUG_FS enabled). + +What: /sys/class/leds/<led>/mc/multi_index +Date: December 2024 +KernelVersion: 6.x +Contact: Jonathan Brophy <professor_jonny@...mail.com> +Description: + Read-only attribute showing the LED color IDs for each channel + in the virtual LED. + + Returns space-separated LED_COLOR_ID_* values (integers) + corresponding to each channel. Channels are ordered by + ascending color ID value (0, 1, 2, 3, ...). + + See include/dt-bindings/leds/common.h for color ID definitions. + + Common color ID values: + - 0: LED_COLOR_ID_WHITE + - 1: LED_COLOR_ID_RED + - 2: LED_COLOR_ID_GREEN + - 3: LED_COLOR_ID_BLUE + - 4: LED_COLOR_ID_AMBER + - 5: LED_COLOR_ID_VIOLET + - 6: LED_COLOR_ID_YELLOW + - 7: LED_COLOR_ID_IR + - 8: LED_COLOR_ID_MULTI + - 9: LED_COLOR_ID_RGB + - 10: LED_COLOR_ID_UV + + Example (RGB LED): + $ cat /sys/class/leds/myled/mc/multi_index + 1 2 3 + (Shows: red=1, green=2, blue=3) + + Example (RGBW LED): + $ cat /sys/class/leds/myled/mc/multi_index + 0 1 2 3 + (Shows: white=0, red=1, green=2, blue=3) + + This attribute is essential for correctly indexing the + multi_intensity and mc-channel-multipliers arrays, especially + when white LEDs are present (which come first due to ID=0). + +What: /sys/class/leds/<led>/mc/multi_multipliers +Date: December 2024 +KernelVersion: 6.x +Contact: Jonathan Brophy <professor_jonny@...mail.com> +Description: + Read-only attribute showing the scale/multiplier values (0-255) + for each color channel. + + Multipliers are defined in device tree via the + "mc-channel-multipliers" property and must be ordered to match + the channel order (sorted by LED_COLOR_ID). + + In multicolor mode, these scale the intensity values: + final = (intensity * multiplier / 255) * brightness / max_brightness + + In standard mode, these define the fixed color mix: + final = multiplier * brightness / max_brightness + + Returns space-separated values (0-255), one per channel, in the + same order as multi_index. + + Example (RGB LED): + $ cat /sys/class/leds/myled/mc/multi_index + 1 2 3 + $ cat /sys/class/leds/myled/mc/multi_multipliers + 255 200 150 + (Shows: red=255, green=200, blue=150) + + Example (RGBW warm white): + $ cat /sys/class/leds/myled/mc/multi_index + 0 1 2 3 + $ cat /sys/class/leds/myled/mc/multi_multipliers + 180 255 200 100 + (Shows: white=180, red=255, green=200, blue=100) + +What: /sys/class/leds/<led>/brightness +Date: December 2024 +KernelVersion: 6.x +Contact: Jonathan Brophy <professor_jonny@...mail.com> +Description: + Control the overall brightness of the virtual LED. + + This is the standard LED class attribute. For virtual grouped + LEDs, this controls the master brightness that scales all + physical LEDs assigned to this virtual LED after per-channel + intensity and multipliers are applied. + + Writing brightness triggers the winner-takes-all arbitration + engine which determines which virtual LED controls the hardware + based on: + 1. Priority (higher wins) + 2. Sequence number (most recent wins on tie) + 3. Only virtual LEDs with brightness > 0 participate + + The winner controls ALL physical LEDs. Physical LEDs not used + by the winner are turned off. + + Range: 0 to max_brightness (typically 0-255) + + Reading returns the current brightness setting. + + Example: + $ echo 128 > /sys/class/leds/myled/brightness + $ cat /sys/class/leds/myled/brightness + 128 + +What: /sys/class/leds/<led>/max_brightness +Date: December 2024 +KernelVersion: 6.x +Contact: Jonathan Brophy <professor_jonny@...mail.com> +Description: + Read-only attribute showing the maximum brightness value. + + For multicolor mode virtual LEDs, this is always 255 to provide + full 8-bit resolution for color mixing. + + For standard mode virtual LEDs, this is the minimum max_brightness + among all physical LEDs referenced by the virtual LED. + + Example: + $ cat /sys/class/leds/myled/max_brightness + 255 -- 2.43.0
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