On Tue, Feb 09, 2021 at 05:19:28PM +0200, Vladimir Oltean wrote:

From: Vladimir Oltean <vladimir.oltean@nxp.com>

Currently br_switchdev_set_port_flag has two options for error handling
and neither is good:
- The driver returns -EOPNOTSUPP in PRE_BRIDGE_FLAGS if it doesn't
  support offloading that flag, and this gets silently ignored and
  converted to an errno of 0. Nobody does this.
- The driver returns some other error code, like -EINVAL, in
  PRE_BRIDGE_FLAGS, and br_switchdev_set_port_flag shouts loudly.

The problem is that we'd like to offload some port flags during bridge
join and leave, but also not have the bridge shout at us if those fail.
But on the other hand we'd like the user to know that we can't offload
something when they set that through netlink. And since we can't have
the driver return -EOPNOTSUPP or -EINVAL depending on whether it's
called by the user or internally by the bridge, let's just add an extack
argument to br_switchdev_set_port_flag and propagate it to its callers.
Then, when we need offloading to really fail silently, this can simply
be passed a NULL argument.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---

The build fails because since I started working on v2 and until I sent
it, Jakub merged net into net-next which contained this fix:
https://patchwork.kernel.org/project/netdevbpf/patch/20210207194733.1811529-1-olteanv@gmail.com/
for which I couldn't change prototype due to it missing in net-next.
I think I would like to rather wait to gather some feedback first before
respinning v3, if possible.