Hi Arnd, On 05/04/2011 03:11 PM, Arnd Bergmann wrote: > On Wednesday 04 May 2011, Subhasish Ghosh wrote: >> CAN requires mail box IDs to be programmed in. But, the socket >> CAN subsystem supports only software filtering of the mail box IDs. >> >> So, the mail box IDs programmed into socket CAN during initialization >> does not propagate into the hardware. This is planned to be a future >> implementation in Socket CAN. >> >> In our case, we support hardware filtering, to work around with this, >> Wolfgang (Socket CAN owner) suggested that we implement >> this using sysfs. >> >> These setting are not for debugging, but to program the mail box IDs >> into the hardware. > > Ok, I see. Can you point me to that discussion? > > Wolfgang, I'm a bit worried by the API being split between sockets and sysfs. > The problem is that once the sysfs API is established, users will start > relying on it, and you can no longer migrate away from it, even when > a later version of the Socket CAN also supports setting through a different > interface. What is the current interface to set mail box IDs in software?
Note that this CAN controller is *very* special. It cannot handle all CAN id's due to a lack or resources. The PRUSS firmware is able to manage just up to 8 different CAN identifiers out of the usual 4096 (12-bit) or even more for the extended CAN ids using 29 bits. There is no other CAN controller with such rather serious limitations and therefore there exists also no appropriate interface. I think using sysfs is OK for such device-specific parameters, at least for the time being. > How hard would it be to implement that feature in Socket CAN? CAN controllers usually provide some kind of hardware CAN id filtering, but in a very hardware dependent way. A generic interface may be able to handle the PRUSS restrictions as well. CAN devices are usually configured through the netlink interface. e.g. $ ip link set can0 up type can bitrate 125000 and such a common interface would be netlink based as well. > Is that something that Subhasish or someone else could to as a prerequisite > to merging the driver? Any ideas on how to handle hardware filtering in a generic way are welcome. I will try to come up with a proposal sooner than later. Wolfgang. _______________________________________________ Socketcan-core mailing list [email protected] https://lists.berlios.de/mailman/listinfo/socketcan-core
