From mboxrd@z Thu Jan 1 00:00:00 1970 From: wg@grandegger.com (Wolfgang Grandegger) Date: Thu, 12 May 2011 09:13:40 +0200 Subject: [PATCH v4 1/1] can: add pruss CAN driver. In-Reply-To: <201105112344.44171.arnd@arndb.de> References: <1303474267-6344-1-git-send-email-subhasish@mistralsolutions.com> <2BFFDAA0A0DE4820876E5549867938EC@subhasishg> <201105112331.47954.arnd@arndb.de> <201105112344.44171.arnd@arndb.de> Message-ID: <4DCB88A4.2010901@grandegger.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 05/11/2011 11:44 PM, Arnd Bergmann wrote: > On Wednesday 11 May 2011, Arnd Bergmann wrote: >> If that interpretation is right, I would seriously recommend rethinking >> the design of the CAN firmware for pruss, so you can start doing something >> useful with the offload engine that fits into the Socket CAN API, or that >> would be a useful extension to Socket CAN that is also implementable in >> the kernel for all other drivers in a meaningful way. > > I've looked some more into the CAN socket implementation, and I suppose that > the idea of the pruss driver was really to help do the work from the > can_rcv_filter function in hardware. That software filter is per socket while the hardware filter will be per device. > Doing this right would really mean supporting both a mode where any new > filter that gets added to socket can ends up being added to the hardware > as long as it fits, similar to how we can add additional unicast mac > addresses to an ethernet NIC. However, when the filters from all user > sockets combined can not be represented in the hardware driver, the hardware > needs to be put into a less efficient mode where all packets are returned > to the kernel and processed in software. Well, that seems sophisticated resulting in a complex implementation (may code line) also because hardware filters are very hardware dependent. Usually just one global filter can be defined. I think that's overkill. A simple interface using: ip link set can0 type can filter : [: ...] would just be fine. Wolfgang.