Hi Alexander,
> > > > > Changes in v2:
> > > > > * Clearly state in the commit log llsec is not supported yet.
> > > > > * Do not use mlme transmission helpers because we don't really need to
> > > > > stop the queue when sending a beacon, as we don't expect any feedback
> > > > > from the PHY nor from the peers. However, we don't want to go through
> > > > > the whole net stack either, so we bypass it calling the subif helper
> > > > > directly.
> > > > >
> > >
> > > moment, we use the mlme helpers to stop tx
> >
> > No, we no longer use the mlme helpers to stop tx when sending beacons
> > (but true MLME transmissions, we ack handling and return codes will be
> > used for other purposes).
> >
>
> then we run into an issue overwriting the framebuffer while the normal
> transmit path is active?
Crap, yes you're right. That's not gonna work.
The net core acquires HARD_TX_LOCK() to avoid these issues and we are
no bypassing the net core without taking care of the proper frame
transmissions either (which would have worked with mlme_tx_one()). So I
guess there are two options:
* Either we deal with the extra penalty of stopping the queue and
waiting for the beacon to be transmitted with an mlme_tx_one() call,
as proposed initially.
* Or we hardcode our own "net" transmit helper, something like:
mac802154_fast_mlme_tx() {
struct net_device *dev = skb->dev;
struct netdev_queue *txq;
txq = netdev_core_pick_tx(dev, skb, NULL);
cpu = smp_processor_id();
HARD_TX_LOCK(dev, txq, cpu);
if (!netif_xmit_frozen_or_drv_stopped(txq))
netdev_start_xmit(skb, dev, txq, 0);
HARD_TX_UNLOCK(dev, txq);
}
Note1: this is very close to generic_xdp_tx() which tries to achieve the
same goal: sending packets, bypassing qdisc et al. I don't know whether
it makes sense to define it under mac802154/tx.c or core/dev.c and give
it another name, like generic_tx() or whatever would be more
appropriate. Or even adapting generic_xdp_tx() to make it look more
generic and use that function instead (without the xdp struct pointer).
Note2: I am wondering if it makes sense to disable bh here as well?
Once we settle, I send a patch.
Thanks,
Miquèl
