netdev - Re: [PATCH] ravb: implement MTU change while device is up

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Date:   Mon, 13 May 2019 14:18:07 +0200
From:   Simon Horman <horms@...ge.net.au>
To:     Ulrich Hecht <uli@...nd.eu>
Cc:     Niklas Söderlund <niklas.soderlund@...natech.se>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        linux-renesas-soc@...r.kernel.org, netdev@...r.kernel.org,
        davem@...emloft.net, wsa@...-dreams.de, magnus.damm@...il.com
Subject: Re: [PATCH] ravb: implement MTU change while device is up

On Thu, May 09, 2019 at 05:32:21PM +0200, Ulrich Hecht wrote:
> 
> > On May 9, 2019 at 12:10 PM Simon Horman <horms@...ge.net.au> wrote:
> > 
> > 
> > On Thu, May 09, 2019 at 08:57:44AM +0200, Ulrich Hecht wrote:
> > > 
> > > > On May 8, 2019 at 6:52 PM Niklas Söderlund <niklas.soderlund@...natech.se> wrote:
> > > > 
> > > > 
> > > > Hi Sergei,
> > > > 
> > > > On 2019-05-08 18:59:01 +0300, Sergei Shtylyov wrote:
> > > > > Hello!
> > > > > 
> > > > > On 05/08/2019 06:21 PM, Ulrich Hecht wrote:
> > > > > 
> > > > > > Uses the same method as various other drivers: shut the device down,
> > > > > > change the MTU, then bring it back up again.
> > > > > > 
> > > > > > Tested on Renesas D3 Draak board.
> > > > > > 
> > > > > > Signed-off-by: Ulrich Hecht <uli+renesas@...nd.eu>
> > > > > 
> > > > >    You should have CC'ed me (as an reviewer for the Renesas drivers).
> > > 
> > > Sorry, will do next time.
> > > 
> > > > > 
> > > > >    How about the code below instead?
> > > > > 
> > > > > 	if (netif_running(ndev))
> > > > > 		ravb_close(ndev);
> > > > > 
> > > > >  	ndev->mtu = new_mtu;
> > > > > 	netdev_update_features(ndev);
> > > > 
> > > > Is there a need to call netdev_update_features() even if the if is not 
> > > > running?
> > > 
> > > In my testing, it didn't seem so.
> > 
> > That may be because your testing doesn't cover cases where it would make
> > any difference.
> 
> Cases other than changing the MTU while the device is up?

I was thinking of cases where listeners are registered for the
notifier that netdev_update_features() triggers.