Re: [PATCH 1/1] hw/net/can: Introduce Xlnx ZynqMP CAN controller for QEMU

[Jason Wang]

On 2020/2/11 上午5:45, Vikram Garhwal wrote:
> > > +                }
> > > +            } else {
> > > +                /* Normal mode Tx. */
> > > +                generate_frame(&frame, data);
> > > +
> > > +                can_bus_client_send(&s->bus_client, &frame, 1);
> > I had a quick glance at can_bus_client_send():
> >
> > It did:
> >
> >       QTAILQ_FOREACH(peer, &bus->clients, next) {
> >           if (peer->info->can_receive(peer)) {
> >               if (peer == client) {
> >                   /* No loopback support for now */
> >                   continue;
> >               }
> >               if (peer->info->receive(peer, frames, frames_cnt) > 0) {
> >                   ret = 1;
> >               }
> >           }
> >       }
> >
> > which looks not correct. We need to use qemu_send_packet() instead of
> > calling peer->info->receive() directly which bypasses filters completely.
> [Vikram Garhwal] Can you please elaborate it bit more on why do we need to 
> filter outgoing message? So, I can either add a filter before sending the 
> packets. I am unable to understand the use case for it. For any message which 
> is incoming, we are filtering it for sure before storing in update_rx_fifo().


I might be not clear, I meant the netfilters supported by qemu which 
allows you to attach a filter to a specific NetClientState, see 
qemu_send_packet_async_with_flags. It doesn't mean the filter 
implemented in your own NIC model.

Thanks


> Also, I can see existing CAN models like CAN sja1000 and CAN Kavser are using it 
> same can_bus_client_send() function. However, this doesn't mean that it is the 
> correct way to send & receive packets.