netdev - Re: [PATCH net-next v2 6/8] dpaa2-switch: reorganize the [pre]changeupper events

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Message-ID: <tkskehfowdrohukyhqu4ae6t56ceuwp6p2mm7r2tfzihladl6t@vxeggsm2ppte>
Date: Fri, 15 Dec 2023 14:08:51 +0200
From: Ioana Ciornei <ioana.ciornei@....com>
To: Simon Horman <horms@...nel.org>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next v2 6/8] dpaa2-switch: reorganize the
 [pre]changeupper events

On Fri, Dec 15, 2023 at 11:49:39AM +0000, Simon Horman wrote:
> On Wed, Dec 13, 2023 at 02:14:09PM +0200, Ioana Ciornei wrote:
> > Create separate functions, dpaa2_switch_port_prechangeupper and
> > dpaa2_switch_port_changeupper, to be called directly when a DPSW port
> > changes its upper device.
> > 
> > This way we are not open-coding everything in the main event callback
> > and we can easily extent when necessary.
> > 
> > Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
> > ---
> > Changes in v2:
> > - none
> > 
> >  .../ethernet/freescale/dpaa2/dpaa2-switch.c   | 76 +++++++++++++------
> >  1 file changed, 52 insertions(+), 24 deletions(-)
> > 
> > diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
> > index d9906573f71f..58c0baee2d61 100644
> > --- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
> > +++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-switch.c
> > @@ -2180,51 +2180,79 @@ dpaa2_switch_prechangeupper_sanity_checks(struct net_device *netdev,
> >  	return 0;
> >  }
> >  
> > -static int dpaa2_switch_port_netdevice_event(struct notifier_block *nb,
> > -					     unsigned long event, void *ptr)
> > +static int dpaa2_switch_port_prechangeupper(struct net_device *netdev,
> > +					    struct netdev_notifier_changeupper_info *info)
> >  {
> > -	struct net_device *netdev = netdev_notifier_info_to_dev(ptr);
> > -	struct netdev_notifier_changeupper_info *info = ptr;
> >  	struct netlink_ext_ack *extack;
> >  	struct net_device *upper_dev;
> >  	int err = 0;
> 
> nit: I don't think that err needs to be initialised here.
> 

Ok.

> >  
> >  	if (!dpaa2_switch_port_dev_check(netdev))
> > -		return NOTIFY_DONE;
> > +		return 0;
> >  
> >  	extack = netdev_notifier_info_to_extack(&info->info);
> > -
> > -	switch (event) {
> > -	case NETDEV_PRECHANGEUPPER:
> > -		upper_dev = info->upper_dev;
> > -		if (!netif_is_bridge_master(upper_dev))
> > -			break;
> > -
> > +	upper_dev = info->upper_dev;
> > +	if (netif_is_bridge_master(upper_dev)) {
> >  		err = dpaa2_switch_prechangeupper_sanity_checks(netdev,
> >  								upper_dev,
> >  								extack);
> >  		if (err)
> > -			goto out;
> > +			return err;
> >  
> >  		if (!info->linking)
> >  			dpaa2_switch_port_pre_bridge_leave(netdev);
> > +	}
> 
> FWIIW, I think that a more idomatic flow would be to return if
> netif_is_bridge_master() is false. Something like this (completely untested!):
> 
> 	if (!netif_is_bridge_master(upper_dev))
> 		return 0;
> 
> 	err = dpaa2_switch_prechangeupper_sanity_checks(netdev, upper_dev,
> 							extack);
> 	if (err)
> 		return err;
> 
> 	if (!info->linking)
> 		dpaa2_switch_port_pre_bridge_leave(netdev);
> 

It looks better but I don't think this it's easily extensible.

I am planning to add support for LAG offloading which would mean that I
would have to revert to the initial flow and extend it to something
like:

	if (netif_is_bridge_master(upper_dev)) {
		...
	} else if (netif_is_lag_master(upper_dev)) {
		...
	}

The same thing applies to the dpaa2_switch_port_changeupper() function
below.

> > +
> > +	return 0;
> > +}
> > +
> > +static int dpaa2_switch_port_changeupper(struct net_device *netdev,
> > +					 struct netdev_notifier_changeupper_info *info)
> > +{
> > +	struct netlink_ext_ack *extack;
> > +	struct net_device *upper_dev;
> > +	int err = 0;
> 
> nit: I don't think err is needed in this function it's value never changes.
> 

Yes, indeed. I'll remove it.