Re: [PATCH v2] iio: adc: ad7173: fix num_slots

[David Lechner <dlechner@baylibre.com>]

On 7/6/25 5:15 AM, Jonathan Cameron wrote:
> On Fri, 4 Jul 2025 12:04:04 -0500
> David Lechner <dlechner@baylibre.com> wrote:
> 
>> On 7/4/25 11:21 AM, David Lechner wrote:
>>> Fix the num_slots value for most chips in the ad7173 driver. The correct
>>> value is the number of CHANNELx registers on the chip.
>>>
>>> In commit 4310e15b3140 ("iio: adc: ad7173: don't make copy of
>>> ad_sigma_delta_info struct"), we refactored struct ad_sigma_delta_info
>>> to be static const data instead of being dynamically populated during
>>> driver probe. However, there was an existing bug in commit 76a1e6a42802
>>> ("iio: adc: ad7173: add AD7173 driver") where num_slots was incorrectly
>>> set to the number of CONFIGx registers instead of the number of
>>> CHANNELx registers. This bug was partially propagated to the refactored
>>> code in that the 16-channel chips were only given 8 slots instead of
>>> 16 although we did managed to fix the 8-channel chips and one of the
>>> 4-channel chips in that commit. However, we botched two of the 4-channel
>>> chips and ended up incorrectly giving them 8 slots during the
>>> refactoring.
>>>
>>> This patch fixes that mistake on the 4-channel chips and also
>>> corrects the 16-channel chips to have 16 slots.
>>>
>>> Fixes: 4310e15b3140 ("iio: adc: ad7173: don't make copy of ad_sigma_delta_info struct")
>>> Signed-off-by: David Lechner <dlechner@baylibre.com>
>>> ---
>>> Changes in v2:
>>> - Improve commit message.
>>> - Link to v1: https://lore.kernel.org/r/20250703-iio-adc-ad7173-fix-num_slots-on-most-chips-v1-1-326c5d113e15@baylibre.com
>>> ---
>>>  drivers/iio/adc/ad7173.c | 37 +++++++++++++++++++++++++++----------
>>>  1 file changed, 27 insertions(+), 10 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/ad7173.c b/drivers/iio/adc/ad7173.c
>>> index dd9fa35555c79ead5a1b88d1dc6cc3db122502be..9c197cea11eb955becf4b9b97246379fa9c5da13 100644
>>> --- a/drivers/iio/adc/ad7173.c
>>> +++ b/drivers/iio/adc/ad7173.c
>>> @@ -771,10 +771,27 @@ static const struct ad_sigma_delta_info ad7173_sigma_delta_info_8_slots = {
>>>  	.num_slots = 8,
>>>  };
>>>  
>>> +static const struct ad_sigma_delta_info ad7173_sigma_delta_info_16_slots = {
>>> +	.set_channel = ad7173_set_channel,
>>> +	.append_status = ad7173_append_status,
>>> +	.disable_all = ad7173_disable_all,
>>> +	.disable_one = ad7173_disable_one,
>>> +	.set_mode = ad7173_set_mode,
>>> +	.has_registers = true,
>>> +	.has_named_irqs = true,  
>>
>>> +	.supports_spi_offload = true,  
>>
>> Well drat, I was too quick with the update and the bots [1] noticed that
>> this conflicts with the in-flight patch that added this field [2].
>>
>> I guess we can drop this one line, but then the other patch will wait
>> until this fix makes its way back into the togreg/testing branches.
> 
> I'm lost - what would you prefer we do here?  For now I have [2] on my
> tree but can drop just that one patch if it unwinds this complexity.

I was hoping you would tell me. :-p

In any case, we should apply this patch, with the supports_spi_offload
line dropped, first so that it backports cleanly to the stable release(s).

But where to apply this patch depends on if you are planning on doing
another fixes-togreg this release cycle or not. Or we could just opt
to take the slow path to avoid the dependency dance and just apply
both patches to iio/togreg and let it make it's way to stable after
the next merge cycle.

>>
>> [1]: https://lore.kernel.org/linux-iio/202507050018.iWEJiG04-lkp@intel.com/
>> [2]: https://lore.kernel.org/linux-iio/20250701-iio-adc-ad7173-add-spi-offload-support-v3-12-42abb83e3dac@baylibre.com/
>>
>>> +	.addr_shift = 0,
>>> +	.read_mask = BIT(6),
>>> +	.status_ch_mask = GENMASK(3, 0),
>>> +	.data_reg = AD7173_REG_DATA,
>>> +	.num_resetclks = 64,
>>> +	.num_slots = 16,
>>> +};
>>> +  
>>
>