Hi,

This series adds a new driver for TI ADS1X18 SPI devices.

This is my first time contributing to the IIO subsystem and making
dt-bindings documentation, so (don't) go easy on me :p.

As explained in Patch 2 changelog, the DRDY interrupt line is shared
with the MOSI pin. This awkward quirk is also found on some Analog
Devices sigma-delta SPI ADCs, so the interrupt and trigger design is
inspired by those.

Thank you in advance for your reviews.

Signed-off-by: Kurt Borja <kuurtb@gmail.com>
---
Kurt Borja (2):
      dt-bindings: iio: adc: Add TI ADS1018/ADS1118
      iio: adc: Add ti-ads1x18 driver

 .../devicetree/bindings/iio/adc/ti,ads1118.yaml    | 132 +++
 MAINTAINERS                                        |   7 +
 drivers/iio/adc/Kconfig                            |  12 +
 drivers/iio/adc/Makefile                           |   1 +
 drivers/iio/adc/ti-ads1x18.c                       | 919 +++++++++++++++++++++
 5 files changed, 1071 insertions(+)
---
base-commit: f9e05791642810a0cf6237d39fafd6fec5e0b4bb
change-id: 20251012-ads1x18-0d0779d06690

-- 
 ~ Kurt

On 11/21/25 11:16 AM, Kurt Borja wrote:
> Hi,
> 
> This series adds a new driver for TI ADS1X18 SPI devices.
> 
> This is my first time contributing to the IIO subsystem and making
> dt-bindings documentation, so (don't) go easy on me :p.

I actually had these parts on my radar, so happy to help you out.
Unfortunately, I don't have the hardware for testing though.

The first thing I was going to do was check the existing drivers
to make sure that there isn't one already that has a compatible
register layout. I have a feeling we won't find one, but would be
good to mention that in the cover to justify adding a new driver.

There are a couple of similar TI ADCs on the mailing list right
now, but they are IMHO just slightly too different to share a
driver, but would be good to look at just to make things are
consistent on a high level.

> 
> As explained in Patch 2 changelog, the DRDY interrupt line is shared
> with the MOSI pin. This awkward quirk is also found on some Analog
> Devices sigma-delta SPI ADCs, so the interrupt and trigger design is
> inspired by those.

Yup, that seems to be the best way we know how to handle this.

Hi David,

On Fri Nov 21, 2025 at 5:32 PM -05, David Lechner wrote:
> On 11/21/25 11:16 AM, Kurt Borja wrote:
>> Hi,
>> 
>> This series adds a new driver for TI ADS1X18 SPI devices.
>> 
>> This is my first time contributing to the IIO subsystem and making
>> dt-bindings documentation, so (don't) go easy on me :p.
>
> I actually had these parts on my radar, so happy to help you out.
> Unfortunately, I don't have the hardware for testing though.
>
> The first thing I was going to do was check the existing drivers
> to make sure that there isn't one already that has a compatible
> register layout. I have a feeling we won't find one, but would be
> good to mention that in the cover to justify adding a new driver.

The closest driver I could find was the ti-ads1015 I2C driver. It has
the same register map and similar specs. Although I think we can adapt
it to be "compatible", I chose to do a different driver for a few
reasons:

  - ads1015 and compatible devices have a separate DRDY interrupt line.

  - The ti-ads1015 driver doesn't support the DRDY interrupt (sleeps
    until data is ready and it doesn't have an iio_trigger).

  - To correctly handle the DOUT/DRDY line we need to manually control
    the spi_bus_lock. And we do it differently based on which IIO device
    mode we are operating on, so it would be difficult to stuff this
    logic into regmap_bus callbacks alone.

  - IMO the end result of merging these drivers would be too messy.

This is just my opinion though, so let me know what you think. If do
agree I will add some of this points in the patch changelog!

>
> There are a couple of similar TI ADCs on the mailing list right
> now, but they are IMHO just slightly too different to share a
> driver, but would be good to look at just to make things are
> consistent on a high level.

Yes, the other two TI ADCs, ADS1120 and ADS131M02 are very different
devices.

>
>> 
>> As explained in Patch 2 changelog, the DRDY interrupt line is shared
>> with the MOSI pin. This awkward quirk is also found on some Analog
>> Devices sigma-delta SPI ADCs, so the interrupt and trigger design is
>> inspired by those.
>
> Yup, that seems to be the best way we know how to handle this.


-- 
 ~ Kurt

On 11/21/25 5:28 PM, Kurt Borja wrote:
> Hi David,
> 
> On Fri Nov 21, 2025 at 5:32 PM -05, David Lechner wrote:
>> On 11/21/25 11:16 AM, Kurt Borja wrote:
>>> Hi,
>>>
>>> This series adds a new driver for TI ADS1X18 SPI devices.
>>>
>>> This is my first time contributing to the IIO subsystem and making
>>> dt-bindings documentation, so (don't) go easy on me :p.
>>
>> I actually had these parts on my radar, so happy to help you out.
>> Unfortunately, I don't have the hardware for testing though.
>>
>> The first thing I was going to do was check the existing drivers
>> to make sure that there isn't one already that has a compatible
>> register layout. I have a feeling we won't find one, but would be
>> good to mention that in the cover to justify adding a new driver.
> 
> The closest driver I could find was the ti-ads1015 I2C driver. It has
> the same register map and similar specs. Although I think we can adapt
> it to be "compatible", I chose to do a different driver for a few
> reasons:
> 
>   - ads1015 and compatible devices have a separate DRDY interrupt line.
> 
>   - The ti-ads1015 driver doesn't support the DRDY interrupt (sleeps
>     until data is ready and it doesn't have an iio_trigger).

I don't think this one is a big deal. Ideally, eventually both drivers
would support operating both with and without interrupts.

> 
>   - To correctly handle the DOUT/DRDY line we need to manually control
>     the spi_bus_lock. And we do it differently based on which IIO device
>     mode we are operating on, so it would be difficult to stuff this
>     logic into regmap_bus callbacks alone.
> 
>   - IMO the end result of merging these drivers would be too messy.

This one I agree with 100%, but for different reasons. ads1015 is I2C
and ads1018 is SPI _and_ regmap is not a good fit for either of these.
Mostly because when reading sample data, we need a custom SPI message
to read the data and write the setup for the next conversion at the
same time. And ads1018 only has 1 register anyway that isn't 100%
identical to the same register in ads1015.

> 
> This is just my opinion though, so let me know what you think. If do
> agree I will add some of this points in the patch changelog!
> 
In the end, we both have the same conclusion.