The gadget ethernet driver supports changing the MTU, but only allows this when the USB cable is removed. The comment indicates that this is because the "peer won't know". Even if the network link is still down and only the USB link is established, the driver won't allow the change.
Other network interfaces allow changing the MTU any time, and don't force the link to be disabled. This makes perfect sense, because in order to be able to negotiate the MTU, the link needs to be up. Remove the restriction so that it is now actually possible to change the MTU (e.g. using "ifconfig usb0 mtu 15000") without having to manually pull the plug or change the driver's default setting. This is especially important after commit bba787a860fa: "usb: gadget: ether: Allow jumbo frames". Signed-off-by: Mike Looijmans <mike.looijm...@topic.nl> --- drivers/usb/gadget/function/u_ether.c | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c index 6554322..9c60e57 100644 --- a/drivers/usb/gadget/function/u_ether.c +++ b/drivers/usb/gadget/function/u_ether.c @@ -144,20 +144,12 @@ static inline int qlen(struct usb_gadget *gadget, unsigned qmult) static int ueth_change_mtu(struct net_device *net, int new_mtu) { struct eth_dev *dev = netdev_priv(net); - unsigned long flags; - int status = 0; - /* don't change MTU on "live" link (peer won't know) */ - spin_lock_irqsave(&dev->lock, flags); - if (dev->port_usb) - status = -EBUSY; - else if (new_mtu <= ETH_HLEN || new_mtu > GETHER_MAX_ETH_FRAME_LEN) - status = -ERANGE; - else - net->mtu = new_mtu; - spin_unlock_irqrestore(&dev->lock, flags); + if (new_mtu <= ETH_HLEN || new_mtu > GETHER_MAX_ETH_FRAME_LEN) + return -ERANGE; + net->mtu = new_mtu; - return status; + return 0; } static void eth_get_drvinfo(struct net_device *net, struct ethtool_drvinfo *p) -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/