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From:   "Sa, Nuno" <Nuno.Sa@analog.com>
To:     Jonathan Cameron <jic23@kernel.org>,
        "Pop, Cristian" <Cristian.Pop@analog.com>
CC:     "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
        "linux-gpio@vger.kernel.org" <linux-gpio@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "robh+dt@kernel.org" <robh+dt@kernel.org>
Subject: RE: [PATCH v2 2/2] one-bit-adc-dac: Add initial version of one bit
 ADC-DAC
Thread-Topic: [PATCH v2 2/2] one-bit-adc-dac: Add initial version of one bit
 ADC-DAC
Thread-Index: AQHYBuEH6Xi3N0MJ30e3Zm8eCa4LKaxlkU8AgASOs1A=
Date:   Wed, 19 Jan 2022 09:38:45 +0000
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References: <20220111115919.14645-1-cristian.pop@analog.com>
        <20220111115919.14645-2-cristian.pop@analog.com>
 <20220116115228.1f7b4728@jic23-huawei>
In-Reply-To: <20220116115228.1f7b4728@jic23-huawei>
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Hi Jonathan,

> From: Jonathan Cameron <jic23@kernel.org>
> Sent: Sunday, January 16, 2022 12:52 PM
> To: Pop, Cristian <Cristian.Pop@analog.com>
> Cc: linux-iio@vger.kernel.org; linux-gpio@vger.kernel.org; linux-
> kernel@vger.kernel.org; devicetree@vger.kernel.org;
> robh+dt@kernel.org
> Subject: Re: [PATCH v2 2/2] one-bit-adc-dac: Add initial version of one
> bit ADC-DAC
>=20
> [External]
>=20
> On Tue, 11 Jan 2022 13:59:19 +0200
> Cristian Pop <cristian.pop@analog.com> wrote:
>=20
> > This allows remote reading and writing of the GPIOs. This is useful in
> > application that run on another PC, at system level, where multiple
> iio
> > devices and GPIO devices are integrated together.
> Hi Cristian,
>=20
> So I fully understand why this can be useful, but it is a software only
> construction so I'm not convinced that it makes sense to necessarily
> configure it via device tree.   A better fit may well be configfs.
> (note I always meant to add configfs controls for iio_hwmon but
> haven't
> found the time to do it yet...)
>=20
> As it currently stands, doing only polled / sysfs reads this driver doesn=
't
> do enough to justify its existence. You could just do all this in
> userspace
> using the existing gpio interfaces.  So to be useful I'd expect it to
> at least do triggered buffer capture.
>=20
> When we have talked about handling digital signals int he past we
> discussed
> whether the IIO channel description would also benefit from tighter
> packing
> than the current minimum of a byte per channel.  Perhaps we don't

That reminded me about this series [1] Alex tried to upstream. It's slightl=
y
related and this was all about supporting buffered channels with less than
8 bits (IIRC). I didn't went through the all thread but I remember you had =
some
"questions" about the whole thing. That series is something that I definite=
ly want
to revive at some point (might be that I just need to change things in ADI =
kernel)
to stop having these custom patches in our tree.

> technically
> 'need' it here but if we do add it in future it will be hard to retrofit =
into
> this driver without big userspace ABI changes (i.e. breaking all existing
> users).

I think this is the perfect opportunity to add support for it (either with =
the series
I mentioned or something else) if we ever really want to have this in IIO.=
=20


[1]: https://lore.kernel.org/linux-iio/20200424051818.6408-1-alexandru.arde=
lean@analog.com/
- Nuno S=E1
=20