A valid CAN dataframe can have a data length code (DLC) of 0 .. 8 data bytes.

When reading the CAN controllers register the 4-bit value may contain values
from 0 .. 15 which may exceed the reserved space in the socket buffer!

The ISO 11898-1 Chapter 8.4.2.3 (DLC field) says that register values > 8
should be reduced to 8 without any error reporting or frame drop.

This patch introduces a new helper macro to cast a given 4-bit data length
code (dlc) to __u8 and ensure the DLC value to be max. 8 bytes.

The different handlings in the rx path of the CAN netdevice drivers are fixed.
Signed-off-by: NOliver Hartkopp <oliver@hartkopp.net>
Signed-off-by: NWolfgang Grandegger <wg@grandegger.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Not all hardcoded values have been replaced as this made the code quite
unreadable. IMHO this compromise serves the purpose of readability.
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

As suggested by Wolfgang Grandegger.
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

- use extern where apropriate
- don't export symbols
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The upper layer does not support it yet.
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

- remove whitespaces
- use ! and ?: when apropriate
- make braces consistent
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Taken from socketcan-svn, fixed remaining todos, cleaned up, tested with a
phyCORE-MPC5200B-IO and a custom board.
Signed-off-by: NWolfram Sang <w.sang@pengutronix.de>
Cc: Wolfgang Grandegger <wg@grandegger.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>