Messages in this thread | | | Date | Wed, 15 Mar 2023 11:34:18 -0700 | Subject | Re: [PATCH net 1/2] net: dsa: don't error out when drivers return ETH_DATA_LEN in .port_max_mtu() | From | Florian Fainelli <> |
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On 3/14/23 11:24, Vladimir Oltean wrote: > Currently, when dsa_slave_change_mtu() is called on a user port where > dev->max_mtu is 1500 (as returned by ds->ops->port_max_mtu()), the code > will stumble upon this check: > > if (new_master_mtu > mtu_limit) > return -ERANGE; > > because new_master_mtu is adjusted for the tagger overhead but mtu_limit > is not. > > But it would be good if the logic went through, for example if the DSA > master really depends on an MTU adjustment to accept DSA-tagged frames. > > To make the code pass through the check, we need to adjust mtu_limit for > the overhead as well, if the minimum restriction was caused by the DSA > user port's MTU (dev->max_mtu). A DSA user port MTU and a DSA master MTU > are always offset by the protocol overhead. > > Currently no drivers return 1500 .port_max_mtu(), but this is only > temporary and a bug in itself - mv88e6xxx should have done that, but > since commit b9c587fed61c ("dsa: mv88e6xxx: Include tagger overhead when > setting MTU for DSA and CPU ports") it no longer does. This is a > preparation for fixing that. > > Fixes: bfcb813203e6 ("net: dsa: configure the MTU for switch ports") > Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> -- Florian
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