linux-kernel - Re: [PATCH v6 7/8] iio: dac: ad3552r: add high-speed platform driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c6emj4i56zozdpkgx6gkzgdlnwvkagll6g2yc6naumnrxqkvee@5ktdjfsem5bj>
Date: Wed, 16 Oct 2024 10:35:26 +0200
From: Angelo Dureghello <adureghello@...libre.com>
To: Nuno Sá <noname.nuno@...il.com>
Cc: David Lechner <dlechner@...libre.com>, 
	Nuno Sá <nuno.sa@...log.com>, Lars-Peter Clausen <lars@...afoo.de>, 
	Michael Hennerich <Michael.Hennerich@...log.com>, Jonathan Cameron <jic23@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, 
	Conor Dooley <conor+dt@...nel.org>, Olivier Moysan <olivier.moysan@...s.st.com>, 
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH v6 7/8] iio: dac: ad3552r: add high-speed platform driver

On 15.10.2024 17:00, Nuno Sá wrote:
> On Tue, 2024-10-15 at 09:38 -0500, David Lechner wrote:
> > On 10/15/24 1:37 AM, Nuno Sá wrote:
> > > On Mon, 2024-10-14 at 16:15 -0500, David Lechner wrote:
> > > > On 10/14/24 5:08 AM, Angelo Dureghello wrote:
> > > > > From: Angelo Dureghello <adureghello@...libre.com>
> > > > > 
> > > > > Add High Speed ad3552r platform driver.
> > > > > 
> > > > 
> > > > ...
> > > > 
> > > > > +static int ad3552r_hs_read_raw(struct iio_dev *indio_dev,
> > > > > +			       struct iio_chan_spec const *chan,
> > > > > +			       int *val, int *val2, long mask)
> > > > > +{
> > > > > +	struct ad3552r_hs_state *st = iio_priv(indio_dev);
> > > > > +	int ret;
> > > > > +
> > > > > +	switch (mask) {
> > > > > +	case IIO_CHAN_INFO_SAMP_FREQ: {
> > > > > +		int sclk;
> > > > > +
> > > > > +		ret = iio_backend_read_raw(st->back, chan, &sclk, 0,
> > > > > +					   IIO_CHAN_INFO_FREQUENCY);
> > > > 
> > > > FWIW, this still seems like an odd way to get the stream mode SCLK
> > > > rate from the backend to me. How does the backend know that we want
> > > > the stream mode clock rate and not some other frequency value? 
> > > 
> > > In this case the backend has a dedicated compatible so sky is the limit :). But
> > > yeah,
> > > I'm also not extremely happy with IIO_CHAN_INFO_FREQUENCY. But what do you have
> > > in
> > > mind? Using the sampling frequency INFO or a dedicated OP?
> > > 
> > 
> > It think it would be most straightforward to have something
> > like a iio_backend_get_data_stream_clock_rate() callback since
> > that is what we are getting.
> 
> Hmmm, what about exporting an actual clock? Maybe it's overkill but from a
> correctness point of view, seems what we should actually do :)
> 
> > 
> > Re: the other recent discussions about getting too many
> > callbacks. Instead of a dedicated function like this, we
> > could make a set of generic functions:
> > 
> > iio_backend_{g,s}et_property_{s,u}(8, 16, 32, 64}()
> > 
> 
> Hmm interesting approach. I don't dislike it. Kind of a generic getter/setter thingy.
> We could then still have optional inline helpers that would call the generic
> functions with the proper enum value.
> 
> > that take an enum parameter for the property. This way,
> > for each new property, we just have to add an enum member
> > instead of creating a get/set callback pair.
> > 
> > Unrelated to this particular case, but taking the idea even
> > farther, we could also do the same with enable/disable
> > functions. We talked before about cutting the number of
> > callbacks in half by using a bool parameter instead of
> > separate enable/disable callbacks. But we could cut it down
> > even more by having an enum parameter for the thing we are
> > enabling/disabling.
> 
> If we don't get too strict about types it could even fall into the above u8 category.
> 
> Instead of lot of new simple ops we just grow an enum.

so a single call for all enable/disable calls. Looks good to me.

What we want to do now ?

So if understand, we don't like too much IIO_CHAN_INFO_FREQUENCY
but at the same time, we don't want to have several new calls in the
backend proposing a design change at this stage, where the patch
was (likely) in a good shape.

What about to simply add a IIO_CHAN_INFO_BUS_CLK or similar ? 

> 
> - Nuno Sá
>