From: Andrew Lunn <andrew@lunn.ch>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
Vivien Didelot <vivien.didelot@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <jakub.kicinski@netronome.com>,
netdev <netdev@vger.kernel.org>
Subject: Re: [PATCH net-next 1/3] net: dsa: Configure the MTU for switch ports
Date: Sun, 24 Nov 2019 23:43:21 +0100 [thread overview]
Message-ID: <20191124224321.GC6009@lunn.ch> (raw)
In-Reply-To: <CA+h21hpcvGZavmSZK3KEjfKVDt6ySw2Fv42EVfp5HxbZoesSqg@mail.gmail.com>
> Correct. I was actually held back a bit while looking at Andrew's
> patch dc0fe7d47f9f ("net: dsa: Set the master device's MTU to account
> for DSA overheads") where he basically discarded errors, so that's the
> approach I took too (thinking that some DSA masters would not have ops
> for changing or reporting the MTU).
Ignoring errors is deliberate because some master interfaces just
worked without having to set the MTU. I was worried that some that
just worked did not implement MTU changes, so i could not error out.
And my experience when things did not work was mostly the MTU did not
matter, but MRU did. The MAC would send frames with a header, but not
receive them with the header. Setting the MTU actually seems to set
the MRU on most MACs.
But when you are thinking about jumbo frames, i would not ignore the
error. We do need to be sure the master interface can support jumbo,
and big enough jumbo to support the header.
Andrew
next prev parent reply other threads:[~2019-11-24 22:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-23 19:48 [PATCH net-next 0/3] Configure the MTU on DSA switches Vladimir Oltean
2019-11-23 19:48 ` [PATCH net-next 1/3] net: dsa: Configure the MTU for switch ports Vladimir Oltean
2019-11-23 20:27 ` Florian Fainelli
2019-11-23 20:46 ` Vladimir Oltean
2019-11-23 21:14 ` Florian Fainelli
2019-11-23 21:29 ` Vladimir Oltean
2019-11-23 21:47 ` Florian Fainelli
2019-11-23 21:54 ` Vladimir Oltean
2019-11-24 22:43 ` Andrew Lunn [this message]
2019-11-23 20:51 ` Vladimir Oltean
2019-11-23 21:09 ` Florian Fainelli
2019-11-24 22:48 ` Andrew Lunn
2019-11-23 19:48 ` [PATCH net-next 2/3] net: dsa: sja1105: Implement the port MTU callbacks Vladimir Oltean
2019-11-23 20:30 ` Florian Fainelli
2019-11-23 20:48 ` Vladimir Oltean
2019-11-23 19:48 ` [PATCH net-next 3/3] net: dsa: vsc73xx: Make the MTU configurable Vladimir Oltean
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