From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 722701FBEA8; Mon, 18 May 2026 13:45:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779111948; cv=none; b=oIIgYVCm+8NCYf8SeHiNNgkGe+lcRKCw1aJuefqV4cRxfGc701HL2ezuOszI6eDXphRYESnJGNAvJLoMeuJuk50MR05fu38DtWkrsjsxcnR2WpvKSw37pLlL3wYgtofGV22EGrALR193JdxxUbTacUl6f3jCaT0uyHCQwfRd7eY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779111948; c=relaxed/simple; bh=tDAoFGFvkYgyrEHwppvlh3HDSU8G12IrZS59be5EKkg=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=VFkOhEd08F2f/0vrQee9KaXCG5kFbegYY0SRkDSOwFQSUSvrvxEOUCIkqWxQHA8M6NXhNTg87IZH5gg8ke9ku/yXzrjcdg/kKx0ffbiYctOJ6WEruzQCUZTw0gE00lQvrzPssufJtkL4bbz6xYMkqNKhPMsexO1cyEC/umheLFQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=heX+I03Q; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="heX+I03Q" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4FB59C2BCB7; Mon, 18 May 2026 13:45:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779111948; bh=tDAoFGFvkYgyrEHwppvlh3HDSU8G12IrZS59be5EKkg=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=heX+I03QVitiX4hw+zKWoFscXe7oBjinLU0dWj9eY1K6sRjGPJ+NSu+rnvQX7hBE8 cxcTT3gb0Pk+0bB26m8pSI1Uy6cBNpxREtEcEXZ70wIg2LtnmXLOoUyCeVBqn8qiJu 05wpvokNiQMg6+AWzX5jj3hmbDfyyFK/i8I5AJ+S2VLXoxCMiiiym1/8MsIDSFIpfF 5isotSAgu5EEi9gPc2Mka4g2BBQMm7bBvWYnFXOIc2LTORXypRLTUVoctQplHLqze9 ZZootCwkbYou8Sj0ftL9nXVhyabwMsKnEKRQxdisCOLqc1o18i0BqSMnBM6MTMu3pn KQK7K+upptsng== Date: Mon, 18 May 2026 14:45:37 +0100 From: Jonathan Cameron To: Rodrigo Alencar <455.rodrigo.alencar@gmail.com> Cc: Rodrigo Alencar via B4 Relay , rodrigo.alencar@analog.com, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-hardening@vger.kernel.org, Lars-Peter Clausen , Michael Hennerich , David Lechner , Andy Shevchenko , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Philipp Zabel , Jonathan Corbet , Shuah Khan , Kees Cook , "Gustavo A. R. Silva" Subject: Re: [PATCH RFC v4 09/10] Documentation: ABI: testing: add docs for ad9910 sysfs entries Message-ID: <20260518144537.7c998308@jic23-huawei> In-Reply-To: References: <20260508-ad9910-iio-driver-v4-0-d26bfd20ee3d@analog.com> <20260508-ad9910-iio-driver-v4-9-d26bfd20ee3d@analog.com> <20260517155843.7f833658@jic23-huawei> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-doc@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 Sun, 17 May 2026 18:30:27 +0100 Rodrigo Alencar <455.rodrigo.alencar@gmail.com> wrote: > On 26/05/17 03:58PM, Jonathan Cameron wrote: > > On Fri, 08 May 2026 18:00:25 +0100 > > Rodrigo Alencar via B4 Relay wrote: > > > > > From: Rodrigo Alencar > > > > > > Add custom ABI documentation file for the DDS AD9910 with sysfs entries to > > > control Parallel Port, Digital Ramp Generator and OSK parameters. > > > > > > Signed-off-by: Rodrigo Alencar > > I'm fine with phase and frequency as defined, but for the scaling it made me wonder. > > For outvoltage0 channels the assumption the value is the peak voltage so if > > we know what input to be modulated by the ramp generator can we express them > > in volts (well milivolts) rather than as a scaling multiplier? > > The DAC output is current-based and differential. Voltage conversion would happen > outside the device... Why aren't we representing this as out_altcurrentX-Y_xxxx? > using a resistor load or an op-amp transimpedance stage, > and I am no expert on that, but that often requires impedance matching so voltage > levels may depend on the frequency. Then, I suppose that voltage is not the right > unit to use. Understood that it can get complex! > > The scale here controls the amplitude of the varying signal. Assuming the peak voltage > (amplitude) is constant means we have a constant envelope, but that should not mean > we can't control it or it should not mean that the hardware can have other ways to > control it. That said, scale behaves as a "gain multiplier". Understood. Given it's the envelope then if scale happened to be 1 always it would be presented as _processed. So this is consistent with other channel types. > > > > > That seems to me like it fits better with the overall ABI. > > > > > +What: /sys/bus/iio/devices/iio:deviceX/out_altvoltageY_scale_offset > > > +KernelVersion: > > > +Contact: linux-iio@vger.kernel.org > > > +Description: > > > + For a channel that allows amplitude control through buffers, this > > > + represents the value for a base amplitude scale. The actual output > > > + amplitude scale is a result with the sum of this value. > > > + > > > > > + > > > +What: /sys/bus/iio/devices/iio:deviceX/out_altvoltageY_scale_roc > > > > Silly question perhaps but can work out how this related to millivolts/sec > > That might make a more intuitive interface than scaling multiplier per sec > > Perhaps the combination with offset makes this impossible though maybe that > > could be a expressed as a voltage offset? Afterall if the amplitude being > > scaled is 5V then 5 * (offset + scale) = 5 * offset + 5 * scale > > > > > +KernelVersion: > > > +Contact: linux-iio@vger.kernel.org > > > +Description: > > > + Amplitude scale rate of change in 1/s for channels that ramp > > > + amplitude. This value may be influenced by the channel's > > > + sampling_frequency setting. > > > > >