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Message-ID: <e743bcaa-f17c-4a0f-bcb2-b38d02e802cb@roeck-us.net>
Date: Thu, 2 Nov 2023 10:17:15 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Alexandre Belloni <alexandre.belloni@...tlin.com>,
"Miclaus, Antoniu" <Antoniu.Miclaus@...log.com>
Cc: Alessandro Zummo <a.zummo@...ertech.it>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Conor Dooley <conor+dt@...nel.org>,
Jean Delvare <jdelvare@...e.com>,
"linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>
Subject: Re: [PATCH v4 2/2] rtc: max31335: add driver support
On 11/2/23 09:57, Alexandre Belloni wrote:
[ ... ]
>>>> +static int max31335_read_offset(struct device *dev, long *offset)
>>>> +{
>>>> + struct max31335_data *max31335 = dev_get_drvdata(dev);
>>>> + u32 value;
>>>> + int ret;
>>>> +
>>>> + ret = regmap_read(max31335->regmap, MAX31335_AGING_OFFSET,
>>> &value);
>>>> + if (ret)
>>>> + return ret;
>>>> +
>>>> + *offset = value;
>>>
>>> This is super dubious, what is the unit of MAX31335_AGING_OFFSET ?
>>>
>>
>> There is not additional information on the AGING_OFFSET register (no
>> other offset registers).
>> I treated it as a raw value that user can write/read. Should I drop the
>> offset implementation?
>>
>
> The value exposed to userspace is in parts per billion. If you can't do
> the conversion, then you have to drop it.
>
The max31334 datasheet says "Resolution = 0.477ppm". Again, the datasheet for
max31335 is not public, so it is impossible to say what the resolution is
for that chip, but I would assume that it is documented.
Guenter
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