linux-kernel - Re: [PATCH v2] iio: adc: ad7173: fix num

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Message-ID: <20250706111529.360a3095@jic23-huawei>
Date: Sun, 6 Jul 2025 11:15:29 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>, Jonathan Cameron
 <Jonathan.Cameron@...wei.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: adc: ad7173: fix num_slots

On Fri, 4 Jul 2025 12:04:04 -0500
David Lechner <dlechner@...libre.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@...libre.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.
> 
> [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,
> > +};
> > +  
>