[RFC PATCH 0/2] leds: flash: LM3643 dual LED flash driver

[Rillian Grant <rillian.grant@gmail.com>]

This series adds a flash LED driver for the Texas Instruments
LM3643. I wrote it to support the Windows Hello NIR illuminator on my
ThinkPad X9-15 Gen 1, which appears to have a single LED connected to
both current sources. All non-error code paths have been tested on my
device.

This device is enumerated by ACPI (HID TXNW3643) as an I2C client with
no _DSD. The driver, following the leds/flash convention, sees no LED
child nodes and fails to probe. For testing I have been using an SSDT
overlay.

On Windows, Lenovo distributes an LM3643 driver authored by Intel. Its
inf file matches on the HID alone and contains a default intensity for
each LED, 100% for LED1 and 60% for LED2, which suggests the driver
applies a static configuration to any enumerated LM3643.

I am sending this RFC to ask how best to supply this default static
configuration. The options I can see are:

1. A DMI-matched table, similar to touchscreen_dmi.c, that attaches
   LED child nodes on verified boards. I haven't found any existing
   examples of this being done for LED child nodes.
2. A generic fallback in the driver exposing both current sources as
   independent LEDs. However this would apply to all matches without
   a firmware description.

I'd appreciate any guidance on the preferred approach.

Rillian Grant (2):
  dt-bindings: leds: Document TI LM3643 dual LED flash driver
  leds: flash: Add support for the TI LM3643 dual LED flash driver

 .../devicetree/bindings/leds/ti,lm3643.yaml   | 126 +++
 MAINTAINERS                                   |   7 +
 drivers/leds/flash/Kconfig                    |  12 +
 drivers/leds/flash/Makefile                   |   1 +
 drivers/leds/flash/leds-lm3643.c              | 775 ++++++++++++++++++
 5 files changed, 921 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/leds/ti,lm3643.yaml
 create mode 100644 drivers/leds/flash/leds-lm3643.c


base-commit: a4ff2be345d0abc943da8dd8da98151843b750dc
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2.55.0