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Wed, 26 Mar 2025 11:34:02 -0700 (PDT) Date: Wed, 26 Mar 2025 15:35:04 -0300 From: Marcelo Schmitt To: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= Cc: Lars-Peter Clausen , Michael Hennerich , Jonathan Cameron , Nuno =?iso-8859-1?Q?S=E1?= , linux-iio@vger.kernel.org Subject: Re: [PATCH v2 2/3] iio: adc: ad7124: Remove ability to write filter_low_pass_3db_frequency Message-ID: References: <20250317115247.3735016-5-u.kleine-koenig@baylibre.com> <20250317115247.3735016-7-u.kleine-koenig@baylibre.com> Precedence: bulk X-Mailing-List: linux-iio@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250317115247.3735016-7-u.kleine-koenig@baylibre.com> On 03/17, Uwe Kleine-König wrote: > There are several issues with the function that implements writing to > the filter_low_pass_3db_frequency property: > > - The sinc3 factor should be 0.272 not 0.262 (this is fixed for the > reading side in the previous patch). > - For freq > 1 the if condition is always true so the sinc4 filter is > hardly ever chosen. > - In the nearly always taken if branch the filter is set to sinc3, but > the frequency is set for sinc4. (And vice versa in the else branch.) > > This is broken enough to justify the claim that there isn't any serious > user. Also it it counter-intuitive that setting the 3db frequency > modifies the sample frequency and the filter type. Not from engineering background but, as a Linux developer, I agree changing 3dB frequency to set the ODR (sampling frequency) is counter-intuitive and uncommon among other IIO sigma-delta ADC drivers. > > So drop the ability to write that property. > > Signed-off-by: Uwe Kleine-König Reviewed-by: Marcelo Schmitt