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Mon, 12 Jan 2026 05:21:09 -0800 (PST) Message-ID: Subject: Re: [PATCH 2/2] iio: adc: ad9467: make iio backend optional From: Nuno =?ISO-8859-1?Q?S=E1?= To: Jonathan Cameron Cc: Tomas Melin , Michael Hennerich , Nuno Sa , Lars-Peter Clausen , David Lechner , Andy Shevchenko , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Date: Mon, 12 Jan 2026 13:21:51 +0000 In-Reply-To: <20260111114109.28b01266@jic23-huawei> 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> <997f9d13f44031170a4518abf23ee6806d526054.camel@gmail.com> <20260111114109.28b01266@jic23-huawei> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.2 Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sun, 2026-01-11 at 11:41 +0000, Jonathan Cameron wrote: > On Mon, 05 Jan 2026 14:57:02 +0000 > Nuno S=C3=A1 wrote: >=20 > > On Mon, 2026-01-05 at 13:06 +0200, Tomas Melin wrote: > > > Hi, > > >=20 > > > On 21/12/2025 22:00, Jonathan Cameron wrote:=C2=A0=20 > > > > On Tue, 16 Dec 2025 11:40:06 +0000 > > > > Tomas Melin wrote: > > > > =C2=A0=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 coup= led > > > > > to the backend or the services it provides. > > > > >=20 > > > > > Signed-off-by: Tomas Melin =C2=A0=20 > > > > Hi Tomas, > > > > =C2=A0=20 > > > > > =C2=A0static int ad9467_probe(struct spi_device *spi) > > > > > @@ -1352,21 +1361,25 @@ static int ad9467_probe(struct spi_device= *spi) > > > > > =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 */=C2=A0=20 > > > >=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.=C2=A0=20 > > >=20 > > > Having the backend as optional is about flexibility to incorporate th= ese > > > 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-backe= nd > > > approach > > > =C2=A0- simple backend that is not configurable, no need for a dedica= ted > > > driver. The backend (FPGA) sits and waits for data and handles it whe= n > > > it arrives=C2=A0=20 > >=20 > > Agree on the above. Ideally we could have some dummy backend for the ab= ove but > > it is not really easy/maintainable to have it. >=20 > When we say the backend needs no driver, where does the data end up? > Is the idea that it goes into some processing pipeline and sent to > some external path that we have no visibility of? i.e. We configure the > data capture in Linux but never see the data? Yes, that's also my assumption about Tomas's usecase. - Nuno S=C3=A1