Re: [PATCH v2 3/4] staging: iio: magnetometer: Add QST QMC5883P driver

[David Lechner <dlechner@baylibre.com>]

On 4/12/26 4:54 AM, Hardik Phalet wrote:
> On Sat Apr 11, 2026 at 1:32 AM IST, David Lechner wrote:
>> On 4/9/26 4:07 PM, Hardik Phalet wrote:
>>
>> This is a little bit much to review all in one patch. Could be nice
>> to split out power management to a separate patch.
>>

...

>>> +static IIO_DEVICE_ATTR(downsampling_ratio, 0644, downsampling_ratio_show,
>>> +		       downsampling_ratio_store, 0);
>>> +static IIO_CONST_ATTR(downsampling_ratio_available, "1 2 4 8");
>>
>> As mentioned in the cover letter, we'd like to know more about what
>> this actually does. If there is a good reason it doesn't fit with
>> any existing filter attribute, then we'll need a patch to document
>> the sysfs ABI as well.
>>
> In the device datasheet, OSR2("Down sampling ratio") is mentioned like this:
> "Another filter is added for better noise performance; the depth can be
> adjusted through OSR2". OSR2's defintion is called "down sampling ratio"
> in a table. Nowhere else. I didn't know what attribute to map it to in
> this case.
> 
I wonder if there is an application note or something that explains it
in more detail if the datasheet does not.

We could always omit the feature if no one knows what it actually does.