linux-kernel - Re: [PATCH 2/6] iio: adc: ad7606: fix issue/quirk with find

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Message-ID: <1dbc8e19-d6fd-42dd-b116-f08c408b6a5c@baylibre.com>
Date: Mon, 21 Oct 2024 14:31:15 -0500
From: David Lechner <dlechner@...libre.com>
To: Alexandru Ardelean <aardelean@...libre.com>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Cc: jic23@...nel.org, krzk+dt@...nel.org, robh@...nel.org, lars@...afoo.de,
 michael.hennerich@...log.com, gstols@...libre.com
Subject: Re: [PATCH 2/6] iio: adc: ad7606: fix issue/quirk with find_closest()
 for oversampling

On 10/21/24 2:03 PM, David Lechner wrote:
> On 10/21/24 8:02 AM, Alexandru Ardelean wrote:
>> There's a small issue with setting oversampling-ratio that seems to have
>> been there since the driver was in staging.
>> Trying to set an oversampling value of '2' will set an oversampling value
>> of '1'. This is because find_closest() does an average + rounding of 1 + 2,
>> and we get '1'.
>>
>> This is the only issue with find_closest(), at least in this setup. The
>> other values (above 2) work reasonably well. Setting 3, rounds to 2, so a
>> quick fix is to round 'val' to 3 (if userspace provides 2).
> 
> This sounds like a bug in find_closest() instead of in this driver.
> 
> If there is an exact match in the list, it seems reasonable to expect
> that the exact match is returned by find_closest().
> 

Likely also affected by this bug since they have values 1, 2 in the list:

* rtq6056_adc_set_average()
* si1133_scale_to_swgain()