[PATCH v3 0/3] iio: adc: add new ad7380 driver

[David Lechner <dlechner@baylibre.com>]

This series is adding a new driver for the Analog Devices Inc. AD7380,
AD7381, AD7383, and AD7384 ADCs. These chips are part of a family of
simultaneous sampling SAR ADCs.

One quirk of these chips is that since they are simultaneous sampling,
they have multiple SPI data output lines that allow transferring two
data words (one for each input channel) at the same time. So a new
generic devicetree binding is added to describe this sort of SPI bus
configuration.

To keep things simple, the initial driver implementation only supports
the 2-channel differential chips listed above. There are also 4-channel
differential chips and 4-channel single-ended chips in the family that
can be added later.

Furthermore, the driver is just implementing basic support for capturing
data. Additional features like interrupts, CRC, etc. can be added later.

Also, FYI, this driver will also be used as the base for an upcoming
series adding AXI SPI Engine offload support for these chips along with
[1].

This work is being done by BayLibre and on behalf of Analog Devices Inc.
hence the maintainers are @analog.com.

[1]: https://lore.kernel.org/linux-spi/20231204-axi-spi-engine-series-2-v1-0-063672323fce@baylibre.com/

---
Changes in v3:
- dt-bindings:
    - Picked up Conor's Reviewed-By on the adi,ad7380 bindings
- driver:
    - Removed extra indent in DEFINE_AD7380_DIFFERENTIAL_2_CHANNEL macro
    - Removed scan mask that included timestamp channel
    - Removed parent device assignment
    - Picked up Nuno's Reviewed-by
- Link to v2: https://lore.kernel.org/r/20231213-ad7380-mainline-v2-0-cd32150d84a3@baylibre.com

Changes in v2:
- dt-bindings:
    - Added new patch with generic spi-rx-bus-channels property
    - Added maxItems to reg property
    - Replaced adi,sdo-mode property with spi-rx-bus-channels
    - Made spi-rx-bus-channels property optional with default value of 1
      (this made the if: check more complex)
    - Changed example to use gpio for interrupt
- driver:
    - Fixed CONFIG_AD7380 in Makefile
    - rx_buf = st->scan_data.raw instead of rx_buf = &st->scan_data
    - Moved iio_push_to_buffers_with_timestamp() outside of if statement
    - Removed extra blank lines
    - Renamed regulator disable function
    - Dropped checking of adi,sdo-mode property (regardless of the actual
      wiring, we can always use 1-wire mode)
    - Added available_scan_masks
    - Added check for missing driver match data
- Link to v1: https://lore.kernel.org/r/20231208-ad7380-mainline-v1-0-2b33fe2f44ae@baylibre.com

---
David Lechner (3):
      dt-bindings: spi: add spi-rx-bus-channels peripheral property
      dt-bindings: iio: adc: Add binding for AD7380 ADCs
      iio: adc: ad7380: new driver for AD7380 ADCs

 .../devicetree/bindings/iio/adc/adi,ad7380.yaml    | 107 +++++
 .../bindings/spi/spi-peripheral-props.yaml         |  12 +
 MAINTAINERS                                        |  10 +
 drivers/iio/adc/Kconfig                            |  16 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/ad7380.c                           | 462 +++++++++++++++++++++
 6 files changed, 608 insertions(+)
---
base-commit: 18f78b5e609b19b56237f0dae47068d44b8b0ecd
change-id: 20231208-ad7380-mainline-e6c4fa7dbedd