Re: [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:

quoted

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.

quoted

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

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