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Mon, 05 Jan 2026 06:56:20 -0800 (PST) Message-ID: <997f9d13f44031170a4518abf23ee6806d526054.camel@gmail.com> Subject: Re: [PATCH 2/2] iio: adc: ad9467: make iio backend optional From: Nuno =?ISO-8859-1?Q?S=E1?= To: Tomas Melin , Jonathan Cameron Cc: Michael Hennerich , Nuno Sa , Lars-Peter Clausen , David Lechner , Andy Shevchenko , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 05 Jan 2026 14:57:02 +0000 In-Reply-To: <356a75b0-dc3e-4d10-a827-1af3b4ab638f@vaisala.com> References: <20251216-b4-ad9467-optional-backend-v1-0-83e61531ef4d@vaisala.com> <20251216-b4-ad9467-optional-backend-v1-2-83e61531ef4d@vaisala.com> <20251221200014.29af7df8@jic23-huawei> <356a75b0-dc3e-4d10-a827-1af3b4ab638f@vaisala.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Mon, 2026-01-05 at 13:06 +0200, Tomas Melin wrote: > Hi, >=20 > On 21/12/2025 22:00, Jonathan Cameron wrote: > > On Tue, 16 Dec 2025 11:40:06 +0000 > > Tomas Melin wrote: > >=20 > > > Not all users can or want to use the device with an iio-backend. > > > For these users, let the driver work in standalone mode, not coupled > > > to the backend or the services it provides. > > >=20 > > > Signed-off-by: Tomas Melin > > Hi Tomas, > >=20 > > > =C2=A0static int ad9467_probe(struct spi_device *spi) > > > @@ -1352,21 +1361,25 @@ static int ad9467_probe(struct spi_device *sp= i) > > > =C2=A0 indio_dev->channels =3D st->info->channels; > > > =C2=A0 indio_dev->num_channels =3D st->info->num_channels; > > > =C2=A0 > > > + /* Using a backend is optional */ > >=20 > > I'll largely defer to Nuno on the backend aspects but I would like a > > lot more than a statement that it is optional in this comment. > > At least something about where the data goes and what a real system > > that didn't provide a backend would look like etc. >=20 > Having the backend as optional is about flexibility to incorporate these > devices as fits best with the system. The current backend approach is > pretty much dictated with how the ADI default backend is implemented. > These devices are fully configurable via SPI interface so the backend > doesn't necessarily need to be anything fancy or even configurable. >=20 > So there is atleast two use cases that promote the optional iio-backend > approach > =C2=A0- simple backend that is not configurable, no need for a dedicated > driver. The backend (FPGA) sits and waits for data and handles it when > it arrives Agree on the above. Ideally we could have some dummy backend for the above = but it is not really easy/maintainable to have it. > -=C2=A0 custom backend not compatible with the adi backend features. For > example different approach to calibration, or other model for data > channels etc. I would argue the above would require a new driver with, perhaps, a new com= patible on the frontend side for the needed modifications. Or we could introduce so= me kind of "detect backend vendor thing" so that the frontend driver can adapt at r= untime (though this looks like a "fancier" way of having a new compatible). Ideally we could somehow "detect" backend capabilities but these kind of sy= stems are so different and usecase specific that, at least for now, I don't see how t= hat could be sanely done. - Nuno S=C3=A1 >=20