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Message-ID: <20250130162909.00001573@huawei.com>
Date: Thu, 30 Jan 2025 16:29:09 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: David Lechner <dlechner@...libre.com>
CC: Jonathan Santos <Jonathan.Santos@...log.com>, <linux-iio@...r.kernel.org>,
<devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<lars@...afoo.de>, <Michael.Hennerich@...log.com>,
<marcelo.schmitt@...log.com>, <jic23@...nel.org>, <robh@...nel.org>,
<krzk+dt@...nel.org>, <conor+dt@...nel.org>, <jonath4nns@...il.com>,
<marcelo.schmitt1@...il.com>
Subject: Re: [PATCH v2 05/16] Documentation: ABI: add wideband filter type
to sysfs-bus-iio
On Mon, 27 Jan 2025 19:32:45 -0600
David Lechner <dlechner@...libre.com> wrote:
> On 1/27/25 9:12 AM, Jonathan Santos wrote:
> > The Wideband Low Ripple filter is used for AD7768-1 Driver.
> > Document wideband filter option into filter_type_available
> > attribute.
> >
> > Signed-off-by: Jonathan Santos <Jonathan.Santos@...log.com>
> > ---
> > v2 Changes:
> > * Removed FIR mentions.
> > ---
> > Documentation/ABI/testing/sysfs-bus-iio | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-bus-iio b/Documentation/ABI/testing/sysfs-bus-iio
> > index f83bd6829285..9b879e7732cd 100644
> > --- a/Documentation/ABI/testing/sysfs-bus-iio
> > +++ b/Documentation/ABI/testing/sysfs-bus-iio
> > @@ -2291,6 +2291,8 @@ Description:
> > * "sinc3+pf2" - Sinc3 + device specific Post Filter 2.
> > * "sinc3+pf3" - Sinc3 + device specific Post Filter 3.
> > * "sinc3+pf4" - Sinc3 + device specific Post Filter 4.
> > + * "wideband" - filter with wideband low ripple passband
> > + and sharp transition band.
> >
> > What: /sys/.../events/in_proximity_thresh_either_runningperiod
> > KernelVersion: 6.6
>
> I'm a bit shy to make any more suggestions on this one since my previous
> suggestions were clearly not the "right way". :-)
>
> But, the key takeaway I got from the discussion on v1 is that this describes the
> _shape_ of the filter. To me, "wideband" describes the size but not the shape.
> Would rectangular be the correct shape?
>
It's tricky. The filter definition is really vague! No filter is ever rectangular.
Also, I've just noticed. This one is fully programable. It could be anything!
I kind of hope no one cares about that feature as it looks really tricky to support.
Wideband normally means 'flattish to a wide range of frequencies'. Not sure
how best to convey that.
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