Message-ID: <20251230082336.3308403-1-professorjonny98@gmail.com>
Date: Tue, 30 Dec 2025 21:23:13 +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 v5 0/7] leds: Add virtual LED group driver with priority arbitration

From: Jonathan Brophy <professor_jonny@...mail.com>

This patch series introduces a new LED driver that implements virtual LED
groups with priority-based arbitration for shared physical LEDs. The driver
provides a multicolor LED interface while solving the problem of multiple
subsystems needing to control the same physical LEDs.

Key features:
- Winner-takes-all priority-based arbitration
- Full multicolor LED ABI compliance
- Two operating modes (multicolor and standard/fixed-color)
- Deterministic channel ordering by LED_COLOR_ID
- Comprehensive debugfs telemetry (when CONFIG_DEBUG_FS enabled)
- Optimized memory footprint (~200 bytes per LED in production builds)

Use cases:
- System status indicators with boot/error/update priority levels
- RGB lighting with coordinated control
- Multi-element LED arrays unified into single logical controls

The series includes:
1. New LED function identifier for virtual LEDs
2. Device tree bindings for virtual LED class
3. Device tree bindings for virtual LED group controller
4. ABI documentation for sysfs interface
5. Comprehensive driver documentation
6. fwnode_led_get() helper for firmware-agnostic LED resolution
7. Complete driver implementation

Changes since v3 commit
- convert driver to pure fwnode
- +Multicolor LED ABI compliance - standard multi_intensity/multi_index attributes
- Winner-takes-all arbitration - deterministic control with sequence-based tie-breaking
- Proper LED reference management - fwnode_led_get() + led_put() prevents leaks
- 30% memory reduction - conditional debug compilation
- Global ownership tracking - prevents conflicts between multiple controllers
- Hierarchical locking - documented 3-tier lock order prevents deadlocks
- Lock-free hardware I/O - concurrent vLED updates during physical LED access
- Dual operating modes - multicolor (dynamic) and standard (fixed-color) modes
- Pre-allocated arbitration buffers - zero allocations in hot path
- Comprehensive power management - suspend/resume with runtime PM support

Changes since v4 commit
- fix yaml validation errors after feedback from maintainers from LKML

Additional highlights:
- Update batching for software PWM workloads
- Gamma correction for perceptual brightness
- Rate limiting for runaway updates
- Extensive debugfs telemetry with stress testing
- Deferred probe handling for late-probing LEDs
- Removal race prevention with atomic flags

Future enhancements planned:
- dynamic led creation Chardev Interface like uleds
- ubus/ dbus wrapper for linux and openwrt (out of tree)
- addressable rgb support WS2812B/SK6812
- readonly leds for important kernel/ functions

Testing:
- Tested on ARM64 platform with GPIO and PWM LEDs
- Stress tested with 10,000 iterations
- Validated suspend/resume cycles
- Memory leak detection passes

Jonathan Brophy (7):
  dt-bindings: leds: Add LED_FUNCTION_VIRTUAL_STATUS identifier
  dt-bindings: leds: Add virtual LED class bindings
  dt-bindings: leds: Add virtual LED group controller bindings
  ABI: Add sysfs documentation for leds-group-virtualcolor
  leds: Add driver documentation for leds-group-virtualcolor
  leds: Add fwnode_led_get() for firmware-agnostic LED resolution
  leds: Add virtual LED group driver with priority arbitration

 .../sysfs-class-led-driver-virtualcolor       |  168 +
 .../leds/leds-class-virtualcolor.yaml         |  197 +
 .../leds/leds-group-virtualcolor.yaml         |  170 +
 .../leds/leds-group-virtualcolor.rst          |  641 ++++
 drivers/leds/led-class.c                      |  136 +-
 drivers/leds/leds.h                           |  758 +++-
 drivers/leds/rgb/Kconfig                      |   17 +
 drivers/leds/rgb/Makefile                     |    1 +
 drivers/leds/rgb/leds-group-virtualcolor.c    | 3360 +++++++++++++++++
 include/dt-bindings/leds/common.h             |    3 +
 10 files changed, 5399 insertions(+), 52 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-class-led-driver-virtualcolor
 create mode 100644 Documentation/devicetree/bindings/leds/leds-class-virtualcolor.yaml
 create mode 100644 Documentation/devicetree/bindings/leds/leds-group-virtualcolor.yaml
 create mode 100644 Documentation/leds/leds-group-virtualcolor.rst
 create mode 100644 drivers/leds/rgb/leds-group-virtualcolor.c

--
2.43.0

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