Re: [PATCH v2 09/10] iio: adc: ad7476: Support ROHM BD79105

[Matti Vaittinen <mazziesaccount@gmail.com>]

On 08/08/2025 11:54, Nuno Sá wrote:
> On Fri, Aug 08, 2025 at 09:11:03AM +0300, Matti Vaittinen wrote:
>> On 07/08/2025 16:01, Nuno Sá wrote:
>>> On Thu, Aug 07, 2025 at 12:35:25PM +0300, Matti Vaittinen wrote:
>>>> The ROHM BD79105 is a simple 16-bit ADC accessible via SPI*.
>>>>
>>>> The BD79105 has a CONVSTART pin, which must be set high to start the ADC
>>>> conversion. Unlike with the ad7091 and ad7091r which also have a
>>>> CONVSTART pin, the BD79105 requires that the pin must remain high also
>>>> for the duration of the SPI access.
>>>>
>>>> (*) Couple of words about the SPI. The BD79105 has pins named as
>>>> CONVSTART, SCLK, DIN and DOUT. For the curious reader, DIN is not SPI
>>>> ISO.
>>>>
>>>> DIN is a signal which can be used as a chip-select. When DIN is pulled
>>>> low, the ADC will output the completed measurement via DOUT as SCLK is
>>>> clocked. According to the data-sheet, the DIN can also be used for
>>>> daisy-chaining multiple ADCs. Furthermore, DOUT can be used also for a
>>>> 'data-ready' -IRQ. These modes aren't supported by this driver.
>>>>
>>>> Support reading ADC scale and data from the BD79105 using SPI, when DIN
>>>> is used as a chip-select.
>>>>
>>>> Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
>>>> ---
>>>> Revision history:
>>>>    v1 => v2:
>>>>    - Fix the conversion delay for the BD79105
>>>>    - Drop unnecessary GPIO check from the convstart disable
>>>>    - Drop unintended whitespace change
>>>>    - Fix spelling
>>>> ---
>>>

...

>>
>> ...I see two other options. One is adding the check in probe as you suggest.
> 
> I do think this is the right approach. We should make sure no one tries
> to probe this device without any gpio because it will be pretty much
> useless so better to fail probe in the first place.

I Agree.

> I'm also not sure
> it's that complicated. Maybe just a chip_info flag like
> 'convgpio_mandatory' (likelly a bad name) and act accordingly when
> checking the return value.

Just sent v3 couple of minutes ago, and this was exactly what I did. 
(although with another name for the flag).

Thanks! :)

Yours,
	-- Matti