leds: dynamic: Add Dynamic Lighting class interface and Aura (hid-asus) support - #17

Document the Dynamic Lighting LED class ABI and user-facing sysfs
interface.

Describe the common attributes, the visibility rules for optional
controls, the discoverability attributes used by programmable devices,
and the current write semantics for the direct and frame binary
interfaces.

Also add the new document to the LED documentation index and register
it in MAINTAINERS.

Signed-off-by: Marco Scardovi <scardracs@disroot.org>

Add Dynamic Lighting class support to hid-asus for Aura-capable ROG
keyboards and chassis lightbars.

The driver discovers the keyboard layout and lightbar presence through
the Aura probe report. When a lightbar is present, it registers:
- "aura:global": global aggregate node operating directly on
  AURA_ZONE_ALL (0) with zone_type="global"
- "aura:keyboard": independent keyboard controller operating on
  AURA_ZONE_KEY1..4 with zone_type="keyboard" or "keyboard_per_key"
- "aura:lightbar": independent lightbar controller operating on native
  hardware zones AURA_ZONE_BAR_LEFT and AURA_ZONE_BAR_RIGHT with
  zone_type="lightbar"

On models without a lightbar, it registers only "aura:keyboard".

A runtime sysfs attribute "aura_mode" is exposed on all registered
Aura nodes, supporting "auto", "unified", and "split" (rendered as
"[auto] unified split"). Under unified mode (the default resolved on
lightbar hardware), commands to "aura:global" broadcast to AURA_ZONE_ALL
while operations on inactive split nodes return -EBUSY. In split mode,
"aura:keyboard" and "aura:lightbar" are driven independently while
operations on "aura:global" return -EBUSY.

For controllers with direct streaming support, expose packed RGB frame
writes through the class direct buffer interface. Drive independent
keyboard and chassis lightbar lighting via the hardware effect engine
(0xb3) across zones 1..4 for keyboard and native hardware zones 6..7
for lightbar, followed by the firmware latch commit sequence (0xb5 SET ->
0xb4 COMMIT -> 0xb5 SET), ensuring setting static or animated effects on
one zone does not touch or interrupt the other.

Unmask keyboard and lightbar hardware power states during probe and
resume using report 0xbd without invalid zone commands. Drive hardware
animation and static effects independently on each zone, committing each
update via the firmware latch sequence (0xb5 SET -> 0xb4 COMMIT ->
0xb5 SET).

Probe the run-mode capability report before advertising supported
effects, fall back to a conservative built-in effect set when the
capability query is unavailable, and validate returned report lengths
before parsing them.

This adds a common sysfs ABI for Aura lighting without regressing the
existing asus::kbd_backlight brightness interface.

Signed-off-by: Marco Scardovi <scardracs@disroot.org>

Expose Dynamic Lighting class attributes on asus::kbd_backlight when
TUF RGB control is supported (kbd_rgb_dev).

Register the keyboard backlight via devm_led_classdev_dynamic_register,
providing native sysfs controls for standard effects (static, breathing,
spectrum cycle, rainbow, strobe), speed, palette colors, and power
state persistence via ACPI WMI method calls (0xb3 and 0xb4).

Preserve legacy kbd_rgb_mode and kbd_rgb_state sysfs attributes under
the device groups for backward compatibility with existing tools.

Signed-off-by: Marco Scardovi <scardracs@disroot.org>

…OG NVMe enclosures

ASUS ROG external NVMe enclosures (such as the ROG STRIX Arion,
USB ID 0b05:1932) are USB mass-storage devices with no HID interface.
Their addressable Aura RGB LEDs hang off an onboard ENE microcontroller
driven via 16-byte vendor SCSI commands on the same LUN as the storage.

Add the leds-asus-aura-scsi driver using a class_interface registered
with the SCSI class. Its add callback matches INQUIRY vendor "ROG" and
model "ESD-S1C", retains the SCSI device while the LED is registered,
and leaves disk ownership and access untouched for the sd driver.
Each matching enclosure exposes a uniquely named Dynamic Lighting device:
asus-aura-scsi-<H_C_T_L>:rgb:indicator.

Hardware animation offloads (Off, Static, Breathing, Strobe, Spectrum
Cycle, Rainbow, Direct streaming), speed (0..4), direction (right/left),
palette, and direct RGB frame streaming via direct_buffer are fully
integrated.

Remove the device from scsi_dh_blist because class-interface discovery
does not require device-handler attachment.

Signed-off-by: Marco Scardovi <scardracs@disroot.org>