[PATCH v7 0/2] iio: adc: add MAX40080 current-sense amplifier driver

This series adds support for the MAX40080, a bidirectional current-sense
amplifier with an integrated 12-bit ADC.

The driver is placed in IIO rather than hwmon because:
  - IIO's scale/raw model naturally exposes the selectable gain ranges and
    lets userspace apply the correct scale per range.
  - Buffered capture support is planned for a follow-up series -- each
    conversion returns a matched current+voltage pair, which maps cleanly
    to IIO's buffered/triggered model.

Changes since v6:
  - Add types.h include (Andy).
  - Remove dead code: i2c_smbus_read_i2c_block_data can't return partial
    reads, so remove the ret != sizeof(buf) check (David).
  - Remove dead code: iv variable initialization not needed as
    max40080_read_iv always writes to *iv before returning (David).

Changes since v5:
  - Fix datasheet URL format in binding -- use stable link without /en/
    path component (Jonathan, Siratul).
  - Use 'adi' compatible prefix instead of 'maxim' -- MAX40080 is an ADI
    product (Conor).
  - Split MAINTAINERS into binding and driver patches (Siratul).
  - Add datasheet link in driver header comment (Siratul).
  - Fix comment style: capital first letter + period (Siratul).
  - Fix register defines: add register name prefix (CFG_, FIFO_CFG_, IV_)
    and use designated initializers for csa_gain array (Jonathan).
  - Define MAX40080_ADC_RES_BITS and use BIT() for shift (Jonathan).
  - Use lowercase 'mV' in defines (Siratul).
  - Use C99 loop variable declarations (Siratul).
  - Remove braces from single-statement if blocks (Siratul).
  - Declaration and initialization in same statement (Siratul).
  - Use IIO_VAL_FRACTIONAL_LOG2 for voltage scale (Jonathan).
  - Remove unused i2c_set_clientdata call (Jonathan).
  - Use defines instead of magic numbers for range default (Jonathan).

Changes since v4:
  - Initialize tmp = 0 in max40080_read_iv() before read_poll_timeout to
    avoid using potentially uninitialized value in the condition check
    (Sashiko, Jonathan).
  - Simplify max40080_get_oversampling_ratio() to use cached value instead
    of reading from the device (Jonathan).
  - Remove DMA-safe buffer from struct -- I2C layer already bounces data
    internally for i2c_smbus_* calls (Jonathan).
  - Make shunt-resistor-micro-ohms required in DT binding. The default
    1 Ohm was arbitrary and rarely correct for real hardware (Jonathan).
  - Remove PM ops entirely. Having only resume without suspend was flagged
    as "papering over" possible power loss issues (Jonathan).
  - Remove the {} scope around propname, declare it at function top (Andy).
  - Remove mod_devicetable.h include -- i2c.h provides necessary types
    (Jonathan).

Changes since v3:
  - Removed all regmap usage -- regmap doesn't support SMBus PEC or Quick
    Command, both required by this device (Nuno).
  - Fixed locking: max40080_update_bits() now takes the lock internally,
    and callers update cached state after the call returns (Nuno).
  - Consistent comment style: capital first letter + period (Andy).
  - Use propname variable to deduplicate "shunt-resistor-micro-ohms" (Andy).
  - Return IIO_VAL_* inline instead of break + return pattern (Nuno).

Changes since v2:
  - Added shunt-resistor-micro-ohms DT property with default value.
  - Use single-shot mode with SMBus Quick Command trigger for correlated
    current/voltage reads.
  - Precompute current scale per range at probe time.

Link: https://lore.kernel.org/linux-iio/[email protected]/ [v6]
Link: https://lore.kernel.org/linux-iio/[email protected]/ [v5]
Link: https://lore.kernel.org/linux-iio/[email protected]/ [v4]
Link: https://lore.kernel.org/linux-iio/[email protected]/ [v3]
Link: https://lore.kernel.org/linux-iio/[email protected]/ [v2]
Link: https://lore.kernel.org/linux-iio/[email protected]/ [v1]

Stefan Popa (2):
  dt-bindings: iio: adc: add adi,max40080
  iio: adc: add MAX40080 current-sense amplifier driver

 .../bindings/iio/adc/adi,max40080.yaml        |  65 ++
 MAINTAINERS                                   |   9 +
 drivers/iio/adc/Kconfig                       |  11 +
 drivers/iio/adc/Makefile                      |   1 +
 drivers/iio/adc/max40080.c                    | 572 ++++++++++++++++++
 5 files changed, 658 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,max40080.yaml
 create mode 100644 drivers/iio/adc/max40080.c

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2.53.0