From: David Lechner <dlechner@baylibre.com>
To: "Sabau, Radu bogdan" <Radu.Sabau@analog.com>,
"Lars-Peter Clausen" <lars@metafoo.de>,
"Hennerich, Michael" <Michael.Hennerich@analog.com>,
"Jonathan Cameron" <jic23@kernel.org>,
"Sa, Nuno" <Nuno.Sa@analog.com>,
"Andy Shevchenko" <andy@kernel.org>,
"Rob Herring" <robh@kernel.org>,
"Krzysztof Kozlowski" <krzk+dt@kernel.org>,
"Conor Dooley" <conor+dt@kernel.org>,
"Uwe Kleine-König" <ukleinek@kernel.org>,
"Liam Girdwood" <lgirdwood@gmail.com>,
"Mark Brown" <broonie@kernel.org>,
"Linus Walleij" <linusw@kernel.org>,
"Bartosz Golaszewski" <brgl@kernel.org>,
"Philipp Zabel" <p.zabel@pengutronix.de>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <skhan@linuxfoundation.org>
Cc: "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-pwm@vger.kernel.org" <linux-pwm@vger.kernel.org>,
"linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>
Subject: Re: [PATCH v6 4/4] iio: adc: ad4691: add SPI offload support
Date: Mon, 6 Apr 2026 08:56:36 -0500 [thread overview]
Message-ID: <83971700-ea17-4fd5-8985-68c798222800@baylibre.com> (raw)
In-Reply-To: <LV9PR03MB8414BB41577A8B5A0432463FF75DA@LV9PR03MB8414.namprd03.prod.outlook.com>
On 4/6/26 8:30 AM, Sabau, Radu bogdan wrote:
>
>
>> -----Original Message-----
>> From: Sabau, Radu bogdan
>> Sent: Monday, April 6, 2026 2:08 PM
>>
>> ...
>>
>>>>> #define AD4691_CHANNEL(ch)
>>>> \
>>>>> { \
>>>>> .type = IIO_VOLTAGE, \
>>>>> @@ -122,11 +155,9 @@ struct ad4691_chip_info {
>>>>> .info_mask_shared_by_all = BIT(IIO_CHAN_INFO_SCALE),
>>>> \
>>>>> .channel = ch, \
>>>>> .scan_index = ch, \
>>>>> - .scan_type = { \
>>>>> - .sign = 'u', \
>>>>> - .realbits = 16, \
>>>>> - .storagebits = 16, \
>>>>> - }, \
>>>>> + .has_ext_scan_type = 1,
>>>> \
>>>>> + .ext_scan_type = ad4691_scan_types, \
>>>>> + .num_ext_scan_type = ARRAY_SIZE(ad4691_scan_types),
>>>> \
>>>>
>>>> Usually, we just make two separte ad4691_chip_info structs for offload
>>>> vs. not offload.
>>>>
>>>> ext_scan_type is generally only used when the scan type can change
>>>> dynamically after probe.
>>>>
>>>
>>> So, just to be clear, you are saying I should have different chip_info structs
>>> and change the triggered-buffer for offload ones if offload is present?
>>> I am asking since offload has different scan types as well, and this would
>>> mean 3 different chip_info structs for each chip -> total of 12 chip_info
>> structs,
>>> each with a different channel array, or perhaps there is a more compact way
>>> to have this implemented.
>>> I could make the channel arrays use the same macro and have the scan_type
>>> reversed to storage and shift done as parameters.
>>>
>>
>> I have given this a thought and I think this could be done in a more compact
>> way:
>>
>> 1. Parametrize AD4691_CHANNEL to accept storagebits and shift, then define
>> 4 channel
>> arrays:
>>
>> - ad4691_channels[] - 16ch + timestamp (triggered-buffer path)
>> - ad4693_channels[] - 8ch + timestamp (triggered-buffer path)
>> - ad4691_offload_cnv_channels[] - 16 entries, storagebits=32, shift =
>> 0
>> - ad4691_offload_manual_channels[] - 16 entries, storagebits=32,
>> shift=16
>>
>> The two offload arrays are shared across both chip families. Since
>> num_channels
>> bound the interation in the IIO core, the 8ch chips simply use the first 8
>> entries of
>> the 16-entry offload arrays. Triggered-buffer path would need different
>> channel
>> arrays since the timestamp index would be different, and offload doesn't use
>> timestamp.
>>
>> 2. chip_info could then stay at 2 structs, and have channels selected at probe
>> for the
>> indio_dev, or have 4 chip info structs each having its own channels assigned,
>> and only
>> num_channels could be changed at probe.
>>
>
> I also have to mention that the oversampling commit would then implement
> AD4691_MANUAL_CHANNEL macro which would miss the OVERSAMPLING
> infomask, and offload_manual_channels will be declared using it.
> More than this, that commit would also add other ad4691_manual_channels[]
> and ad4693_manual_channels[] arrays that would use that MACRO as well.
>
> Then, chip_info would have ad4691/93_channels assigned to it by default,
> and indio_dev->channels will later be assigned at probe, depending on the
> mode and offload.
>
> If different chip_info structs would be wanted still, then my best guess is
> to have different info structures (perhaps new types) in chip_info by default.
> Something like *sw_info and *offload_info.
Yes, this is how I would do it too.
> Each one would contain all the pre-defined channel arrays in them
> (channels and manual_channels) and so have ad4691_sw_info and ad4691_offload_info.
> After so, chip_info will also contain besides these 2 info structures, num_channels and max_rate.
> At probe indio_dev assignments will be made from the chip_info entirely.
>
> What's your guys take on this? I am keen to hearing your thoughts about this.
>
> Thanks,
> Radu
>
next prev parent reply other threads:[~2026-04-06 13:56 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-03 11:03 [PATCH v6 0/4] iio: adc: ad4691: add driver for AD4691 multichannel SAR ADC family Radu Sabau via B4 Relay
2026-04-03 11:03 ` [PATCH v6 1/4] dt-bindings: iio: adc: add AD4691 family Radu Sabau via B4 Relay
2026-04-03 11:03 ` [PATCH v6 2/4] iio: adc: ad4691: add initial driver for " Radu Sabau via B4 Relay
2026-04-04 14:25 ` David Lechner
2026-04-03 11:03 ` [PATCH v6 3/4] iio: adc: ad4691: add triggered buffer support Radu Sabau via B4 Relay
2026-04-04 15:12 ` David Lechner
2026-04-05 8:57 ` Andy Shevchenko
2026-04-06 9:22 ` Sabau, Radu bogdan
2026-04-06 13:39 ` David Lechner
2026-04-03 11:03 ` [PATCH v6 4/4] iio: adc: ad4691: add SPI offload support Radu Sabau via B4 Relay
2026-04-04 15:34 ` David Lechner
2026-04-06 9:34 ` Sabau, Radu bogdan
2026-04-06 13:44 ` David Lechner
2026-04-06 14:16 ` Sabau, Radu bogdan
2026-04-06 15:02 ` David Lechner
2026-04-07 12:38 ` Sabau, Radu bogdan
2026-04-04 15:57 ` David Lechner
2026-04-06 10:39 ` Sabau, Radu bogdan
2026-04-06 11:08 ` Sabau, Radu bogdan
2026-04-06 13:30 ` Sabau, Radu bogdan
2026-04-06 13:56 ` David Lechner [this message]
2026-04-06 14:20 ` Sabau, Radu bogdan
2026-04-06 13:53 ` David Lechner
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