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SubjectRe: [PATCH v5 2/7] can: bittiming: allow TDC{V,O} to be zero and add can_tdc_const::tdc{v,o,f}_min
On 17.08.2021 00:49:35, Vincent MAILHOL wrote:
> > We have 4 operations:
> > - tdc-mode off switch off tdc altogether
> > - tdc-mode manual tdco X tdcv Y configure X and Y for tdco and tdcv
> > - tdc-mode auto tdco X configure X tdco and
> > controller measures tdcv automatically
> > - /* nothing */ configure default value for tdco
> > controller measures tdcv automatically
>
> The "nothing" does one more thing: it decides whether TDC should
> be activated or not.
>
> > The /* nothing */ operation is what the old "ip" tool does, so we're
> > backwards compatible here (using the old "ip" tool on an updated
> > kernel/driver).
>
> That's true but this isn't the real intent. By doing this design,
> I wanted the user to be able to transparently use TDC while
> continuing to use the exact same ip commands she or he is used
> to using.

Backwards compatibility using an old ip tool on a new kernel/driver must
work. In case of the mcp251xfd the tdc mode must be activated and tdcv
set to the automatic calculated value and tdco automatically measured.

Marc

--
Pengutronix e.K. | Marc Kleine-Budde |
Embedded Linux | https://www.pengutronix.de |
Vertretung West/Dortmund | Phone: +49-231-2826-924 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
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