Re: [Xenomai-help] RTCAN: multiple sockets on one device

[Wolfgang Grandegger <wg@domain.hid>]

Jan Kiszka wrote:
> Daniel Schnell wrote:
>> Hi,
>>  
>> If one opens two sockets to one CAN port and wants to use one socket
>> file descriptor for reading and the other for writing, is it possible to
>> limit the writing socket to _write only_, so it doesn't receive messages
>> ?

Note that the messages are aways received and handled by the ISR. If 
nobody is waiting on messages defined by the filter definitions, they 
will be discarded.

> Option 1: Do not bind the socket, use sendto/sendmsg for transmitting
> (send requires binding).

Yes, this will avoid checking one unnecessary filter definition (a bit 
less overhead). But using just one socket would be fine as well ;-).

> Option 2: Register an impossible filter for the write-only socket. This
> is suboptimal ATM. Actually we should allow registering an empty filter
> list for this purpose. This has been recently discussed on the socketcan
> list, but I'm not aware of any concrete result.

Oliver answered and liked the idea, but there is no agreement yet.

Wolfgang.