From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E103B3D649C; Wed, 27 May 2026 18:32:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779906773; cv=none; b=HZ+xEloL1FB820mJ8PhU5nGjDoILXTkR5TphpHHLu2jHRFBDijaDhj5jHOqw22FRrfvZSSH53hcNA0ARd0TmFQgm4+mHiXSFesC/PHJ67/mDzrFKpm9FW2Cde18i1sXMhZsgOeSqDa+XpP6wnfeACrIg7GZSV5Q4cayBK3F42sI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779906773; c=relaxed/simple; bh=3SmjBOjXXCuAaVGNMBKlr05T7DyebfqzBuFQEOibEbk=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=LMZ6cwxLbZJH9jFvuRqldBC1J+UzGbXBz6R7ugW4Gd8r/QQJfIuVwXJLikjIzK0ANI42IB2cL8S9bnN+XZedtJDq9bIP+Rtlviz5a2pRAnOaV7n7gMCtOhdOZnzDLrZEz/xrH2upBtav88+EF6Oap1rfUO1S6uNn2Ue+s/DKFvA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oc/9JH06; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oc/9JH06" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1DBCD1F000E9; Wed, 27 May 2026 18:32:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1779906771; bh=AtkqO35UtTTwja2Dnv9yfIiRy6VHJUSdpTI3MAmFDm8=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=oc/9JH06FTrPRFhmbAYT4+SaTepnzc/JwIZcXXgwyEZcqHCebfqufsPT8suc0b++k tArO3sezCiW4YmEzQhTNmnHEK0ZQGZOM7xdoUqX0fMUaxjEarbBym3hkfqzBO/d8uS fEsBmZ/vG8LP2MVsGfWU4z4Stmv7XxF9EHf26Plr8wRdVDUCu9CssD8FjNoExLXYQE lNATDuXkvBEGbNMj8mxgd00uDQUtC7+RB+iJaoplX4jBShA9vMf9q0it+4eSHD7Z1m peyxRCLclhAMT0ahQzCSRvFiEEQLrfbr6FdY1HZ/tVh0SoRA0dYiSHfcHHrm/LHmAb k2cxbopdHA1BQ== Date: Wed, 27 May 2026 19:32:41 +0100 From: Jonathan Cameron To: Wadim Mueller Cc: lars@metafoo.de, dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, linux@roeck-us.net, jdelvare@suse.com, ak@it-klinger.de, linux-iio@vger.kernel.org, linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH v1 0/4] iio: add Sensirion SLF3x liquid flow sensor support Message-ID: <20260527193241.308f67b6@jic23-huawei> In-Reply-To: <20260527143515.102794-1-wafgo01@gmail.com> References: <20260524205112.26638-1-wafgo01@gmail.com> <20260526171214.750c2e25@jic23-huawei> <20260527143515.102794-1-wafgo01@gmail.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Wed, 27 May 2026 16:34:58 +0200 Wadim Mueller wrote: > On Tue, 26 May 2026 17:12:14 +0100 > Jonathan Cameron wrote: > > > > 1. Subsystem. Liquid-flow sensors don't seem to have a home in > > > mainline yet. iio/ feels like the natural place for me, but > > > please correct me if hwmon (or somewhere else) is prefered. > > > > I'm fine with this type of sensor in IIO, but open to hear from others! > > Thanks - keeping it in iio/ for v2. > > > > 2. Channel type. IIO has no flow channel type so far. The series > > > adds IIO_VOLUMEFLOW with _scale in litres per second per LSB, > > > so drivers reporting smaller units only need a fractional scale. > > > IIO_MASSFLOW (for gas-flow sensors) was left out on purpose -- > > > happy to add it in the same series if that's more usefull. > > > > Would be good to have a little more detail on difference etc to have > > that discussion. Superficially I'm assuming this is a compressible vs > > non compressible thing? > > Right - that was the distinction I had in mind: > > - IIO_VOLUMEFLOW: volumetric rate (m^3/s in SI, exposed as l/s), > well-defined for an incompressible fluid where the volume at the > sensor equals the volume delivered. This matches all "liquid > flow" sensors I'm aware of (and the SLF3S family in particular). > > - IIO_MASSFLOW: mass rate (kg/s), the natural unit for gases because > the volumetric rate depends on temperature and pressure. Most > "gas flow" parts on the market (Sensirion SFM3xxx, SFC, MFC > devices) actually report a "standard volume flow" (e.g. slm at > 0 degC and 1013 mbar) which is just a fixed-density restatement > of mass flow. Makes sense. > > I left IIO_MASSFLOW out of this series because I don't have a driver > needing it right now, but if you'd prefer I add it as a stub here > (name + ABI entry) so the two siblings land together, I can fold that > in for v2 -- happy either way. > Nope. Good to discuss what it would look like in this over letter, but the actual introduction needs to wait for a driver that uses it. > > > 3. Subdirectory. I put the driver in a new drivers/iio/flow/ > > > since there is no flow subsytem in iio yet. If colocating with > > > drivers/iio/pressure/ (next to sdp500) is preferred I'll respin. > > > > This is easy to change later if we make a wrong decision. For now I think > > iio/flow is fine. > > Sticking with drivers/iio/flow/ for v2. > > Thanks! > > v2 is up, addressing the inline review feedback from you and Guenter. > Dropping the RFC tag since the three high-level questions are > answered. > > Wadim