mirror of
https://github.com/hardkernel/linux.git
synced 2026-06-07 19:30:30 +09:00
80a2fbce45
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>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.