Re: [PATCH v4 0/2] Add support for Analog Devices MAX30210

[Jonathan Cameron <jic23@kernel.org>]

On Thu, 15 Oct 2026 09:21:57 +0800
John Erasmus Mari Geronimo <johnerasmusmari.geronimo@analog.com> wrote:

> This series adds support for the Analog Devices MAX30210 I2C
> temperature sensor.
> 
> The device provides a 16-bit temperature output and includes
> features such as a hardware FIFO, programmable sampling rate,
> threshold alarms, and interrupt support. These capabilities map
> naturally to the IIO subsystem, particularly the buffered interface
> and event framework -- hwmon has no equivalent buffered-capture
> framework, and its alarm attributes are polled rather than
> interrupt-driven, so there is no path to supporting the FIFO or the
> autonomous threshold comparators there.
> 

Thanks for the explanation.  Just to make sure
+CC Guenter and hwmon list.


> Although the MAX30210 belongs to the same device family as the
> MAX30208, it is implemented as a separate driver. The MAX30210 has
> a significantly different feature set, including a 64-sample hardware
> FIFO with configurable watermark interrupts, programmable sampling
> rates, and event support. These features require buffered operation
> and IRQ-driven data handling which are not present in the MAX30208
> driver (which talks to the device directly via i2c_smbus_*() calls
> with no regmap, and has no IIO buffer or event interface at all).
> 
> In addition, the MAX30210 uses a different register map and a more
> flexible I2C address selection scheme. Supporting both devices in a
> single driver would introduce substantial conditional logic, so a
> separate driver keeps the implementation simpler and easier to
> maintain.
> 
> Patch 1 adds the devicetree binding.
> Patch 2 adds the IIO driver implementation.
> 
> Changes since v3:
> https://lore.kernel.org/all/cover.1789032019.git.johnerasmusmari.geronimo@analog.com/
> - regmap_noinc_read() for FIFO reads instead of regmap_bulk_read(),
>   which (combined with regmap caching) could silently return stale
>   cached values of unrelated registers instead of real FIFO data.
> - Mark both bytes of TEMP_DATA_REG volatile for the same reason.
> - Decouple threshold events from the buffer via a refcounted
>   autoconv_get()/autoconv_put() pair, so either can be used
>   independently or concurrently.
> - Don't let a single-shot direct-mode read race with/clobber
>   autonomous conversion mode if a threshold event or the buffer is
>   already using it -- return -EBUSY instead.
> - Don't hard-fail probe when there is no interrupt; fall back to
>   direct-mode-only operation.
> - Fix devm teardown ordering so an in-flight interrupt can't use a
>   freed event interface on removal.
> - Re-assert the powerdown GPIO on removal so the device reaches
>   standby instead of staying powered indefinitely.
> - Style/API fixes from review (register/field grouping, _MASK
>   naming, FIELD_PREP/regmap_assign_bits usage, C99 initializers,
>   dropped redundant i2c_check_functionality() check, comment
>   cleanup).
> 
> All of the above have been verified on real MAX30210 hardware
> (Raspberry Pi 4 test rig), including the no-IRQ fallback, buffer and
> event refcounting (independently and concurrently), rmmod/insmod
> under live interrupts, powerdown GPIO assertion on removal, and FIFO
> flush correctness.
> 
> Changes since v2:
> https://lore.kernel.org/all/20260304122509.67931-1-johnerasmusmari.geronimo@analog.com/
> - Fix FIFO byte-count handling and sample decoding.
> - Fix IIO debug register read/write access.
> - Validate event threshold values and sampling-frequency register values.
> - Return the correct sampling-frequency format and reject direct reads
>   while buffered capture is enabled.
> - Clean up the Kconfig entry and device-tree supply declaration.
> 
> John Erasmus Mari Geronimo (2):
>   dt-bindings: iio: temperature: add ADI MAX30210
>   iio: temperature: add support for Analog Devices MAX30210
> 
>  .../iio/temperature/adi,max30210.yaml         |  61 ++
>  MAINTAINERS                                   |   8 +
>  drivers/iio/temperature/Kconfig               |  13 +
>  drivers/iio/temperature/Makefile              |   1 +
>  drivers/iio/temperature/max30210.c            | 788 ++++++++++++++++++
>  5 files changed, 871 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/temperature/adi,max30210.yaml
>  create mode 100644 drivers/iio/temperature/max30210.c
>