RTEMS | Draft: cpukit: add support for common CAN/CAN FD stack (!49)

[Pavel Pisa (@ppisa)]

Pavel Pisa commented on a discussion on cpukit/dev/can/ctucanfd/ctucanfd_priv.h: https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/49#note_108446

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 > +* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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 > +
 > +#include <dev/can/can-queue.h>
 > +
 > +#ifndef __CTUCANFD_PRIV_H
 > +#define __CTUCANFD_PRIV_H
 > +
 > +#define CTUCANFD_NTXBUFS_MAX ( 8 )

The value has no impact on generic code and for CTU CAN FD the actual number of synthesized buffers is read from hardware. The eight is maximum which can be implemented with actual register sizes and offsets, the Tx priority register needs 4 bits per buffer and its total size is none 32 bit word. And it is required that whole word is rewritten in one go during priorities update. So on 16-bit system only 16-bits and 4 buffers can be implemented. 4 buffers is usual default to keep core of reasonable size as well.

-- 
View it on GitLab: https://gitlab.rtems.org/rtems/rtos/rtems/-/merge_requests/49#note_108446
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