This is more like an RFC patch set since configuration read/write is currently buggy. Change log v1 -> v2: - Took device tree provided by David. - Dropped ABI additions in favor of device tree properties. - Set differential IIO channel subtype for differential ADCs. - Set scan_type shift bits to mask out correct real bits from buffer. - Added __aligned(8) to buffer timestamp. - Used union to reduce buffer memory usage for 16-bit devices. - Used SPI transfer functions rather than SPI message. - Used c99 style structure initialization. - Used iio_device_claim_direct_scoped(). - Removed unneeded pointer casts. - Added other power supplies (VDD and VIO). Link to v1: https://lore.kernel.org/linux-iio/cover.1711131830.git.marcelo.schmitt@xxxxxxxxxx/ Additional topics: - Why there is no different handling for the different SPI wiring modes? It looks like there is no need for different handling of "4-wire" and "3-wire" modes. If in "4-wire" (dt default mode), SDI is connected to SPI controller CS and CNV is active high. We can activate the CNV GPIO then let the SPI controller bring CS (connected to SDI) down when starting the transfer. If in "3-wire" (dt single mode), if we have a CNV (active low) GPIO we activate it and then proceed with with the transfer. If controller CS is connected to CNV it works the same way. I'm thinking it's better if we can support these devices in similar way other SPI ADCs are supported. Does that make sense? To me, the "3-wire" mode with controller CS to ADC CNV is what most resembles conventional SPI. The only important distinction is that the controller must be able to keep ADC SDI line high during conversions. Although, while the spi-engine implementation provided to me can keep SDI up during conversions, I'm not sure its a thing all SPI controllers can do. I tried a raspberry pi 4 some time ago and it was leaving the SDI line low if no tx buffer was provided. Even with a tx full of 1s the controller would bring SDI down between each 8 bits of transfer. Anyway, single-shot and buffered reads work with the spi-engine controller with ADC in "3-wire"/single mode with controller CS line connected to ADC CNV pin which is how I've been testing it. - Why did not make vref regulator optional? Other SAR ADCs I've seen needed a voltage reference otherwise they simply could not provide any reasonable readings. Isn't it preferable to fail rather than having a device that can't provide reliable data? - Why did not split into AD and ADAQ patches? The main difference between AD and ADAQ is the amplifier in front of the ADC. If only supporting AD, we could probably avoid the scale table since it would only have two possible values per ADC. But then the handling of span compression scale would need refactoring to be in the scale table when adding ADAQ. I'm not excited to implement something knowing it will need rework in the following patch. Will do if required. - Span compression and offset. For non-differential ADCs, enabling the span compression requires an input offset. Link: https://www.analog.com/media/en/technical-documentation/data-sheets/AD4000-4004-4008.pdf page 18 and Link: https://www.analog.com/media/en/technical-documentation/data-sheets/ad4002-4006-4010.pdf page 19 I updated the _offset attribute for those ADCs according to span compression being enabled or not. Is it okay to have an attribute update cause an update to another one? Maybe also make the span compression a dt property and have it fixed after probe? - Configuration register Despite it doing single-shot and buffered captures, read and writes to the configuration register are currently buggy. It is as if the register was "floating". I tried setting up buffers like ad7768-1, adxl355_core, bma220_spi, bma400_core, and mcp3911. Thanks, Marcelo Marcelo Schmitt (2): dt-bindings: iio: adc: Add AD4000 iio: adc: Add support for AD4000 .../bindings/iio/adc/adi,ad4000.yaml | 201 ++++++ MAINTAINERS | 8 + drivers/iio/adc/Kconfig | 12 + drivers/iio/adc/Makefile | 1 + drivers/iio/adc/ad4000.c | 649 ++++++++++++++++++ 5 files changed, 871 insertions(+) create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad4000.yaml create mode 100644 drivers/iio/adc/ad4000.c -- 2.43.0
