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SubjectRe: RFC - unclear change in "[media] DiBxxxx: Codingstype updates"
On Mon, Oct 10, 2016 at 08:31:12AM +0200, Patrick Boettcher wrote:
> Hi, der Herr Hofrat ;-)
>
> On Sat, 8 Oct 2016 13:57:14 +0000
> Nicholas Mc Guire <der.herr@hofr.at> wrote:
> > - lo6 |= (1 << 2) | 2;
> > - else
> > - lo6 |= (1 << 2) | 1;
> > + lo6 |= (1 << 2) | 2; //SigmaDelta and Dither
> > + else {
> > + if (state->identity.in_soc)
> > + lo6 |= (1 << 2) | 2; //SigmaDelta and
> > Dither
> > + else
> > + lo6 |= (1 << 2) | 2; //SigmaDelta and
> > Dither
> > + }
> >
> > resulting in the current code-base of:
> >
> > if (Rest > 0) {
> > if (state->config->analog_output)
> > lo6 |= (1 << 2) | 2;
> > else {
> > if (state->identity.in_soc)
> > lo6 |= (1 << 2) | 2;
> > else
> > lo6 |= (1 << 2) | 2;
> > }
> > Den = 255;
> > }
> >
> > The problem now is that the if and the else(if/else) are
> > all the same and thus the conditions have no effect. Further
> > the origninal code actually had different if/else - so I
> > wonder if this is a cut&past bug here ?
>
> I may answer on behalf of Olivier (didn't his address bounce?).
>
> I don't remember the details, this patch must date from 2011 or
> before, but at that time we generated the linux-driver from our/their
> internal sources.
>
> Updates in this area were achieved by a lot of thinking + a mix of trial
> and error (after hours/days/weeks of RF hardware validation).
>
> This logic above has 3 possibilities:
>
> - we use the analog-output, or
> - we are using the digital one, then there is whether we are being in
> a SoC or not (SIP or sinlge chip).
>
> At some point in time all values have been different. In the end, they
> aren't anymore, but in case someone wants to try a different value,
> there are placeholders in the code to easily inject these values.
>
> Now the device is stable, maybe even obsolete. We could remove all the
> branches resulting in the same value for lo6.
>
ok - so as the value for lo6 effectively is the same for all conditions

given (1 << 2) | 2 == 6

this might be simplified to and commented as:

if (Rest > 0) {
/* Based on trial and error */
lo6 |= 6;
Den = 255;
}

let me know if that sounds resonable - just plugging in a magic number
sounds like a bad idea - even if this comment might not be wildly enlightening
it atleast indicates that it is known "magic".

thx!
Der Herr Hofrat

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