Introduce a method to calculate the exact size in bits of a CAN(-FD)
frame with or without dynamic bitstuffing.
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 individual macro definitions, declare the
can_frame_bits() function-like macro. To this extent, do a full
refactoring of the length definitions.
In addition add the can_frame_bytes(). This function-like macro
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)
Function-like macros were chosen over inline functions because they
can be used to initialize const struct fields.
The different maximum frame lengths (maximum data length, 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 as an
alias to, respectively, can_frame_bytes(false, true, CAN_MAX_DLEN) and
can_frame_bytes(true, true, CANFD_MAX_DLEN).
In addition to the above:
- Use ISO 11898-1:2015 definitions for the names of the CAN frame
fields.
- Include linux/bits.h for use of BITS_PER_BYTE.
- Include linux/math.h for use of mult_frac() and
DIV_ROUND_UP(). N.B: the use of DIV_ROUND_UP() is not new to this
patch, but the include was previously omitted.
- Add copyright 2023 for myself.
Suggested-by: Thomas Kopp <Thomas.Kopp@microchip.com>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Reviewed-by: Thomas Kopp <Thomas.Kopp@microchip.com>
Link: https://lore.kernel.org/all/20230611025728.450837-4-mailhol.vincent@wanadoo.fr
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
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