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[90.182.112.124]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49cf75ce49esm117105705e9.1.2026.09.04.05.38.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 04 Sep 2026 05:38:49 -0700 (PDT) Date: Fri, 4 Sep 2026 14:38:48 +0200 From: Joshua Crofts To: Tuna =?UTF-8?Q?K=C4=B1l=C4=B1=C3=A7?= Cc: Jonathan Cameron , David Lechner , Nuno =?ISO-8859-1?Q?S=E1?= , Andy Shevchenko , linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] iio: dac: mcp47a1: Allow full-scale output Message-ID: <20260904143848.00000d7d@gmail.com> In-Reply-To: <20260904122513.175298-1-tuna@tunakilic.com> References: <20260904122513.175298-1-tuna@tunakilic.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.51; x86_64-w64-mingw32) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Hi Tuna, Thanks for the patch! On Fri, 4 Sep 2026 12:25:17 +0000 (UTC) Tuna K=C4=B1l=C4=B1=C3=A7 wrote: > The MCP47A1 has 64 resistors but exposes 65 wiper positions. The valid > DAC codes are 0 through 64, and code 64 selects VREF. >=20 > The driver currently advertises 0 through 63 and uses 64 as the length > argument to in_range(), which also rejects 64. Therefore userspace > cannot select full-scale output. >=20 > Advertise code 64 and make validation cover all 65 codes. Keep 64 as > the scale denominator because the output voltage is VREF multiplied by > the code and divided by 64. >=20 > Fixes: 350d1fb9204b ("iio: dac: mcp47a1: add support for new device") > Signed-off-by: Tuna K=C4=B1l=C4=B1=C3=A7 > --- This makes sense, I must've misread the datasheet... Can I ask how this was found? Manual code analysis or AI? --=20 Kind regards, Joshua Crofts