The previous driver implementation aimed to maximize the amount of
filters, which resulted in a fairly complex implementation.
Background: The bxCAN assigns a number to the filters in the order they
appear in the filter banks. This number is used to match messages in
the FIFO with their filter. If the scale or mode of a filter bank is
changed, all following filter numbers get an offset and the assigned
callbacks have to be shifted accordingly.
The required additional space for the shifting operations resulted in
non-deterministic behaviour and the maximum number of filters could not
be determined at compile-time, which made several tests like
tests/drivers/can/api fail.
This implementation uses a more simple but reliable approach for
filtering and and reserves fixed space for extended and standard ID
filters in the available banks (configurable via Kconfig).
The list mode is not used, which may reduce the total number of usable
filters depending on the application.
The maximum amount of filters is 14 if all filters use ext. IDs,
28 if all use std IDs and something in between if mixed IDs are used.
Also see issue #47986 for more detailed background information.
Signed-off-by: Martin Jäger <martin@libre.solar>
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