can: gw: support modification of Classical CAN DLCs

Add support for data length code modifications for Classical CAN.

The netlink configuration interface always allowed to pass any value
that fits into a byte, therefore only the modification process had to be
extended to handle the raw DLC represenation of Classical CAN frames.

When a DLC value from 0 .. F is provided for Classical CAN frame
modifications the 'len' value is modified as-is with the exception that
potentially existing 9 .. F DLC values in the len8_dlc element are moved
to the 'len' element for the modification operation by mod_retrieve_ccdlc().

After the modification the Classical CAN frame DLC information is brought
back into the correct format by mod_store_ccdlc() which is filling 'len'
and 'len8_dlc' accordingly.

Signed-off-by: Oliver Hartkopp <socketcan@hartkopp.net>
Link: https://lore.kernel.org/r/20201119084921.2621-1-socketcan@hartkopp.net
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
This commit is contained in:
Oliver Hartkopp
2020-11-19 09:49:21 +01:00
committed by Marc Kleine-Budde
parent 396b3cedc9
commit 94c23097f9
2 changed files with 72 additions and 10 deletions

View File

@@ -98,8 +98,8 @@ enum {
/* CAN frame elements that are affected by curr. 3 CAN frame modifications */
#define CGW_MOD_ID 0x01
#define CGW_MOD_DLC 0x02 /* contains the data length in bytes */
#define CGW_MOD_LEN CGW_MOD_DLC /* CAN FD length representation */
#define CGW_MOD_DLC 0x02 /* Classical CAN data length code */
#define CGW_MOD_LEN CGW_MOD_DLC /* CAN FD (plain) data length */
#define CGW_MOD_DATA 0x04
#define CGW_MOD_FLAGS 0x08 /* CAN FD flags */