Sorry for the late reply, I wanted to have this completed earlier but
other imperatives and the time needed to debug decided differently.
On Tue. 23 May 2023 at 15:52, Vincent Mailhol
<mailhol.vincent@xxxxxxxxxx> wrote:
> Introduce a method to calculate the exact size in bits of a CAN(-FD)
> frame with or without dynamic bitsuffing.
>
> These are all the possible combinations taken into account:
>
> - Classical CAN or CAN-FD
> - Standard or Extended frame format
> - CAN-FD CRC17 or CRC21
> - Include or not intermission
>
> Instead of doing several macro definitions, declare the
> can_frame_bits() static inline function. To this extend, do a full
^^^^^^
Typo: extent
(I will not send a v3 just for that).
> refactoring of the length definitions.
>
> If given integer constant expressions as argument, can_frame_bits()
> folds into a compile time constant expression, giving no penalty over
> the use of macros.
>
> Also add the can_frame_bytes(). This function replaces the existing
> macro:
>
> - CAN_FRAME_OVERHEAD_SFF: can_frame_bytes(false, false, 0)
> - CAN_FRAME_OVERHEAD_EFF: can_frame_bytes(false, true, 0)
> - CANFD_FRAME_OVERHEAD_SFF: can_frame_bytes(true, false, 0)
> - CANFD_FRAME_OVERHEAD_EFF: can_frame_bytes(true, true, 0)
>
> The different frame lengths (including intermission) are as follow:
>
> Frame type bits bytes
> ----------------------------------------------------------
> Classic CAN SFF no-bitstuffing 111 14
> Classic CAN EFF no-bitstuffing 131 17
> Classic CAN SFF bitstuffing 135 17
> Classic CAN EFF bitstuffing 160 20
> CAN-FD SFF no-bitstuffing 579 73
> CAN-FD EFF no-bitstuffing 598 75
> CAN-FD SFF bitstuffing 712 89
> CAN-FD EFF bitstuffing 736 92
>
> The macro CAN_FRAME_LEN_MAX and CANFD_FRAME_LEN_MAX are kept to be
> used in const struct declarations (folding of can_frame_bytes() occurs
> too late in the compilation to be used in struct declarations).
To be fair, I am not fully happy with that part. The fact that
can_frame_bits() and can_frame_bytes() can not be used in structure
declaration even if these are compile time constants is unfortunate.
But after reflection, I still see those inline functions as a better
compromise than a collection of macro definitions. Let me know your
thoughts.
(...)
Yours sincerely,
Vincent Mailhol
