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Wed, 17 Dec 2025 01:25:28 -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: Tomas Melin , Michael Hennerich , Nuno Sa , Lars-Peter Clausen , Jonathan Cameron , David Lechner , Andy Shevchenko Cc: "linux-iio@vger.kernel.org" , "linux-kernel@vger.kernel.org" Date: Wed, 17 Dec 2025 09:26:10 +0000 In-Reply-To: References: <20251216-b4-ad9467-optional-backend-v1-0-83e61531ef4d@vaisala.com> <20251216-b4-ad9467-optional-backend-v1-2-83e61531ef4d@vaisala.com> <2a265681ad73bebf1ad7aeea418fb9399b8350cf.camel@gmail.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 Tue, 2025-12-16 at 15:39 +0000, Tomas Melin wrote: > Hi, >=20 > On 16/12/2025 14:56, Nuno S=C3=A1 wrote: > > On Tue, 2025-12-16 at 11:40 +0000, Tomas Melin wrote: > > > 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 > > > --- > >=20 > > Which users? The only usecases (for all the supported devices) we have = require > > the FPGA backend. So do you have a specific usecase for a specific devi= ce? If so, I would > > prefer an explicit boolean in the chip_info struture for the device(s) = we know this > > can happen (unless you have a usecase for all :)). >=20 > This is generically for all the devices supported by the ad9467, not > only a specific device. So it's about how this is used as part of the > design. >=20 > This is aimed at users that do not use the ADI HDL reference backend > with these devices, but instead have custom backends suited for their > own needs. Hmm, ideally I would then like to see the backend driver upstreamed... > In that case, we need to be able to skip the backend registration and > register device as a standalone iio device. >=20 > Hopefully this made the use case clearer? >=20 I mean, I don't love this and I'm not really sure I'm ok with it. These are= fairly high speed devices which often do require an FPGA IP to handle the data flo= w. Now we can ignore the backend device (which is an essential piece) being it expected or not. Or maybe we can just do something like regulators and get a dummy backend o= r just add some fixed kind of backend. Bottom line is, it still seems the backend devi= ce is a core piece in your design and we're just hacking around the driver in way that c= onceptually doesn't make sense to me. Other question that comes to mind (I guess I was not that clear)... Do you = have a real usecase with your own custom backend IP or is this just theoretical? - Nuno S=C3=A1