From: Niklas Cassel <niklas.cas...@axis.com> Date: Tue, 4 Apr 2017 14:18:54 +0200
> From: Niklas Cassel <niklas.cas...@axis.com> > > Setting ethtool ops for stmmac is only allowed when the interface is up. > Setting MTU (a netdev op) for stmmac is only allowed when the interface > is down. > > It seems that the only reason why MTU cannot be changed when running is > that we have not bothered to implement a nice way to dealloc/alloc the > descriptor rings. > > To make it less confusing for the user, call ndo_stop() and ndo_open() > from ndo_change_mtu(). This is not a nice way to dealloc/alloc the > descriptor rings, since it will announce that the interface is being > brought down/up to user space, but there are several other drivers doing > it this way, and it is arguably better than just returning -EBUSY. > > Signed-off-by: Niklas Cassel <niklas.cas...@axis.com> You can't do this with no error handling. Instead, you must do this using a "prepare", "commit" sequence. First making sure you can reallocate all necessary resources, and make the config change, before actually doing so. You're not even checking if the re-open fails, meaning that an MTU change can cause the interface to shut down. That is simply not acceptable.
