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[98.183.112.25]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-5fa36058274sm1427516eaf.40.2025.01.18.09.37.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 18 Jan 2025 09:37:17 -0800 (PST) Message-ID: Date: Sat, 18 Jan 2025 11:37:16 -0600 Precedence: bulk X-Mailing-List: linux-pwm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 8/8] iio: adc: ad4851: add ad485x driver To: =?UTF-8?Q?Nuno_S=C3=A1?= , Antoniu Miclaus , jic23@kernel.org, robh@kernel.org, conor+dt@kernel.org, linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pwm@vger.kernel.org References: <20250117130702.22588-1-antoniu.miclaus@analog.com> <20250117130702.22588-9-antoniu.miclaus@analog.com> From: David Lechner Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 1/18/25 9:10 AM, Nuno Sá wrote: > On Fri, 2025-01-17 at 15:07 +0200, Antoniu Miclaus wrote: >> Add support for the AD485X a fully buffered, 8-channel simultaneous >> sampling, 16/20-bit, 1 MSPS data acquisition system (DAS) with >> differential, wide common-mode range inputs. >> >> Signed-off-by: Antoniu Miclaus >> --- ... > ... > >> +static int ad4851_read_raw(struct iio_dev *indio_dev, >> +    const struct iio_chan_spec *chan, >> +    int *val, int *val2, long info) >> +{ >> + struct ad4851_state *st = iio_priv(indio_dev); >> + >> + switch (info) { >> + case IIO_CHAN_INFO_SAMP_FREQ: >> + *val = st->cnv_trigger_rate_hz / st->osr; >> + return IIO_VAL_FRACTIONAL; >> + case IIO_CHAN_INFO_CALIBSCALE: >> + return ad4851_get_calibscale(st, chan->channel, val, val2); >> + case IIO_CHAN_INFO_SCALE: >> + return ad4851_get_scale(indio_dev, chan, val, val2); > > Maybe this was discussed already and I missed it but I'm a bit puzzled. Don't we > still need OFFSET for differential channels? How do you express negative voltages? > > - Nuno Sá > > It was discussed in early revisions of the series. :-) There was an OFFSET back then, but we removed it because chip uses twos complement encoding for bipolar single-ended and (bipolar) differential. We have 's' and 'u' set in the scan_type.sign in those cases. The current implementation looks correct to me in this regard.