From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f52.google.com (mail-wm1-f52.google.com [209.85.128.52]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3DB513D47D9 for ; Tue, 28 Jul 2026 13:16:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.52 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785244565; cv=none; b=YMzARLnveqZDl85FJoYygRNXBxNzsIg3QZRhuzj42iAkltlYDbLBH+9j+kIkv9KcKg0t6fqvOWmfH1o3LE5lAsVKl/jpD9UQj7yTg9pWb8vZNVJ0rte5OOsZ54mlF3dOxtOLyrIDKwMJI+9C5HATfqsr52KEbD3UrUdH9M56uw4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785244565; c=relaxed/simple; bh=cLH93zo8+5LFvseU1ydD9VGz5QwjgSRbVRGQwkX1r9U=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mXTllst1mrdZddLpJul3kNfAeC+mm6BKV933uYQX+A+LfckR/+Kw62hiToXTxu0AwuQRSYAD0kTXg/HcSXaN8g77q3bAC/7oAR49S8roy6dxqwiSVkkLHn2iHCMgqwGf+lOsS4KedqHl6rBHcPzi+imc0aNcz/YI6jYzGdg+JB8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=WQKjZrB7; arc=none smtp.client-ip=209.85.128.52 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="WQKjZrB7" Received: by mail-wm1-f52.google.com with SMTP id 5b1f17b1804b1-496b7622a83so20035235e9.2 for ; Tue, 28 Jul 2026 06:16:04 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1785244562; x=1785849362; darn=vger.kernel.org; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=NJ8Sz4jZn4MiZdWgUS+toUmyc9X4AmjEUEaGs5iVrDk=; b=WQKjZrB7o3S1TXPjgtNoGkBXQhXmqq/Z3QIfkPsGqHVAEzuozPtaTLqSLKumMTmixh nPccRnQ4jeKaDs8lXgtCNtqCvpiHcf0WD4PTM5XsTeOcMFys4SMXFNxkmzIvTcSmR98J itzJeebwYl1rPHxXST/7FzukBFxIHAQTs7W+pFCQbIfVrCVftIQnBhdlZV/1dS6Eb5Fq 5kYWMz1Y9y5dqNg6/y9oqxWLoF4olZS1Bo2db9s/KUrzPBatfHY/68WBT4bfgW5Zm1gU IzrxZF0QXJd/kfkKIa3SPoThrAUB2LaEhn50ThjAF4n4gTEuC2s0IqybOPsGZ7SDX8yJ FaYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785244562; x=1785849362; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=NJ8Sz4jZn4MiZdWgUS+toUmyc9X4AmjEUEaGs5iVrDk=; b=r3EUfsLWm2R23xsVQeyiaiVeeB60ye9RLKusJfuNg/8w/DKFPm17PYn34fom6gpuWj s/tvbedgw51P5Pu7Vcn3Td1XIkKQlCBOik/zCXdz8qIuJ4ZKntRyfF5P2C8WMk7NKaOk Tm6bKTzpPz8Agjab+q0sCZPrDXHlG/fDKHveU8N8BV19Z9U6LNE4Op7FEo0VgjwVeNNU Qs6ywTdOpybwLqoNtHRdtfsnGYdk/oqfjnXUq/G66sWszF98UnG651bPeZ3zicr4bENY HqVs/EbDgFBTBWmgQspr6wz/zUW3aemGmdlXxIu+UblN5is9YzTosUwr0/qjkNXuX6mk qShQ== X-Forwarded-Encrypted: i=1; AHgh+RoFM0EZqiz0jrdAHX4zYEf3S/XyGuvmBP6P8/oRg673bOOd/DrWhyCJ7BQtmdcR4msnPTbb8rFOFORa@vger.kernel.org X-Gm-Message-State: AOJu0YzfdTpx+J+XNfuJpb31rypwVvKSsRAMsbn1r+XqCiXThrU2tEUQ r6T6Dc+rNiRrtez5FLk54sU6cGSkqEUAVW9w9L6OWUb71UaRUs85gCB+iF9oPg== X-Gm-Gg: AR+sD127PTB5yxlIYXbDPDi/m/738NYykNM93RcNF7QZy2JSDdAA6BhIMCLO6uvao3s ghWVJqDvG442sqH6xvsiJGZ0u/32udxUcl44yQR+kz6cCCietKoJoxkpyqsM0sPSpA9VhSEXWBM ogrEUYrGMN4TzWaPTPIQhxqkpvkRkbBVHMIt67m9t/9BJC9aG3L61jqbGeUmNcOR7qL1Ui/rKG8 Zzh0a61wYU9C3Jf05V7SY1/N5vXNgtLa4GoJ88XFJkVYDbBfr171Olw8EIx9COMteMecLdRqVKB IjXWy/GKEerBKxKfh3baxWKDaNzrBJ505dZ+UfmrP2OEcJlfn/qxRLd37lStNI/aSkcEsdIOK0M FoB1i54lNszuksnRiJL+oaqN7y32fNKWl8bVfB885Nvn7GiXkbohI8WNhX7c50cW15K1X+xJKca yHa+JZ8+B9SV4Gl7Xiz7OkHOVZ/c7AvpF5+/Z7AjfuoPdNWZ0r2lSxGsDZUNp7B1YNgG9PG1nIN 2sI49Fkr17zmatdRSR1kbbQ2/CM5FnB9+IN+5zu3KEGCxAjWbYK4XIcKw/PdVnfJ03GsAk5gTIA bJR4qfOEO74HkNNO/WS07UPtQC0oYm8ASrgeiCP+cRFwokEGMUT4YwtCYtfrfulGM65s43fNY+4 0OwAhYNLd/17p X-Received: by 2002:a05:600c:1d04:b0:495:4e12:6ae5 with SMTP id 5b1f17b1804b1-496c6571d21mr26130575e9.26.1785244562007; Tue, 28 Jul 2026 06:16:02 -0700 (PDT) Received: from localhost (90-182-112-124.rcp.o2.cz. [90.182.112.124]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-496c44af19bsm74777785e9.3.2026.07.28.06.16.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 28 Jul 2026 06:16:01 -0700 (PDT) Date: Tue, 28 Jul 2026 15:15:59 +0200 From: Joshua Crofts To: sashiko-bot@kernel.org Cc: sashiko-reviews@lists.linux.dev, devicetree@vger.kernel.org, conor+dt@kernel.org, robh@kernel.org, linux-iio@vger.kernel.org, jic23@kernel.org, andy@kernel.org, nuno.sa@analog.com, dlechner@baylibre.com Subject: Re: [PATCH v2 2/2] iio: dac: mcp47a1: add support for new device Message-ID: <20260728151559.000067ef@gmail.com> In-Reply-To: <20260727184226.DFC1E1F000E9@smtp.kernel.org> References: <20260727-mcp47a1-add-support-v2-0-d4591a2ce69e@gmail.com> <20260727-mcp47a1-add-support-v2-2-d4591a2ce69e@gmail.com> <20260727184226.DFC1E1F000E9@smtp.kernel.org> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) 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 Mon, 27 Jul 2026 18:42:26 +0000 sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: > - [Medium] Potential off-by-one in DAC scale calculation denominator. > -- Responding to Sashiko's comment. > --- Patch [2]: [PATCH v2 2/2] iio: dac: mcp47a1: add support for new device --- > commit 38bec2fbb020c3f749c52a26e5cc3e78e72eeaf5 > Author: Joshua Crofts > > iio: dac: mcp47a1: add support for new device > > The Microchip MCP47A1 is a 6-bit volatile Digital-to-Analog converter > which communicates via I2C. > > > diff --git a/drivers/iio/dac/mcp47a1.c b/drivers/iio/dac/mcp47a1.c > > new file mode 100644 > > index 0000000000000..140e93ff2ba01 > > --- /dev/null > > +++ b/drivers/iio/dac/mcp47a1.c > [ ... ] > > +static int mcp47a1_read(struct iio_dev *indio_dev, > > + struct iio_chan_spec const *chan, > > + int *val, int *val2, long mask) > > +{ > > + struct mcp47a1_data *data = iio_priv(indio_dev); > > + int ret; > > + > > + switch (mask) { > [ ... ] > > + case IIO_CHAN_INFO_SCALE: > > + *val = data->vref_mV; > > + *val2 = MCP47A1_MAX_STEP; > > [Severity: Medium] > Does this code use the correct denominator for the scale calculation? > > Since this is a 6-bit DAC, shouldn't the scale denominator be 64 (2^6) > instead of the maximum step value of 63? Using MCP47A1_MAX_STEP (63) here > introduces an off-by-one error that could cause userspace to calculate > output voltages with a ~1.5% LSB scaling error when reading the sysfs > attribute. Yes, the max amount of steps is 64, which should be passed here. I'll add a separate macro for this in v3. -- Kind regards, Joshua Crofts