Re: adding can4linux to drivers/char

[Wolfgang Grandegger <wg@grandegger.com>]

On 09/21/2013 11:17 AM, Oliver Hartkopp wrote:
> On 21.09.2013 01:03, Heinz-Jürgen Oertel wrote:
>> Hello Linux CAN community,
>>
>> long before SocketCAN, which now is part of the Linux kernel drivers, can4linux was available as the CAN device driver for Linux.
>>
>> I now like to add it to the kernel source tree as well. What to you think about it. And how should I start and proceed?
>> I would like to start with the Xilinx XCANPS as can be found on the Zynq processor. Maybe also with one PCI board, the CPC-PCI (EMS Wünsche).
>>
>> What is the best way? My current development for the PC is based on OpenSuse with kernel 3.7.10. for Xilinx it is kernel 3.10. Can I send a patch against 3.7 and to whom can I send it?
> 
> Hello Heinz,
> 
> merging the two different approaches makes sense in that way that the
> different users of the can4linux character device API should be able to take
> part of the Linux mainline improvements.
> 
> The question is how to make it a win-win for both sides without doing double work:
> 
> 1. SocketCAN & can4linux users should be able to use a common CAN driver pool
> 2. The netdev and the chardev should be able to run simultaneously
> 3. The chardev API preferably should support all chardev flavours
> 
> Indeed i did some evaluations about the migration from the chardev API of
> can4linux to SocketCAN in my thesis on page 156ff
> 
> (unfortunately in german)
> A.8 Migration existierender CAN Anwendungen
> 
> You might get the thesis from here:
> http://edoc.bibliothek.uni-halle.de/servlets/DocumentServlet?id=9738
> 
> In chapter 8.2 there's a concept describing the co-existence of a character
> device emulator and how to connect it to the existing Linux CAN
> infrastructure. A screenshot from that picture is attached to this mail.
> 
> The advantages of this approach:
> 
> - only one hardware driver pool to maintain (e.g. add Xilinx as netdev driver)
> - SocketCAN and can4linux apps can run simultaneously on the same CAN hardware
> - SocketCAN protocols CAN_BCM and the CAN gateway CAN_GW are still operational
> - a compact and easy maintainable chardev API adapter emulation
> - can4linux API users get access to all existing CAN netdev drivers (USB, ...)
> 
> A real good thing would be if the chardev emulation adapter would support
> different chardev flavours like can4linux, PEAK, LinCAN, ...

*No*, please not, at least not as part of the Linux kernel. People
should port their applications to Linux-CAN and then they will
automatically profit from further improvements.

Wolfgang.