The MAX86150 (Maxim/Analog Devices) combines two PPG optical channels
(Red/IR LED) and one ECG biopotential channel in a single I2C device.
Data is produced at up to 3200 Hz and buffered in a 32-entry hardware
FIFO with a configurable almost-full interrupt.

This patch adds an IIO driver that exposes three channels:

  in_intensity_red_raw   -- PPG Red LED, 19-bit unsigned
  in_intensity_ir_raw    -- PPG IR LED, 19-bit unsigned
  in_voltage0_raw        -- ECG biopotential, 18-bit signed

Key implementation choices:

  - regmap_noinc_read() for FIFO access: reads 9 bytes (3 slots x 3
    bytes) from the streaming FIFO_DATA register in a single I2C
    burst without address auto-increment.

  - IIO hardware trigger backed by the device interrupt (active-low,
    FIFO almost-full). When an interrupt GPIO is provided in the device
    tree, a trigger is registered and wired to the IIO triggered buffer
    path for continuous low-overhead capture.

  - All resource management uses devm_* APIs.

Known limitations to be addressed in v2:
  - IIO_CHAN_INFO_SCALE not yet implemented.
  - Runtime PM (SYS_CTRL SHDN bit) not yet implemented.
  - Not yet tested on physical hardware.

Md Shofiqul Islam (1):
  iio: health: add MAX86150 ECG and PPG biosensor driver

 .../bindings/iio/health/maxim,max86150.yaml   |  67 +++
 drivers/iio/health/Kconfig                    |  23 +
 drivers/iio/health/Makefile                   |   1 +
 drivers/iio/health/max86150.c                 | 512 ++++++++++++++++++
 4 files changed, 603 insertions(+)
 create mode 100755 Documentation/devicetree/bindings/iio/health/maxim,max86150.yaml
 create mode 100755 drivers/iio/health/max86150.c

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2.51.1