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SubjectRe: [PATCH] net: usb: allow MTU that is a multiple of USB packet size
Hello.

On 5/7/2015 12:49 PM, Ruslan Bilovol wrote:

> Current usbnet driver rejects setting MTU that is a multiple
> of USB endpoint's wMaxPacketSize size. However, it may only
> lead to possible performance degradation but is not so
> critical that its using should be prohibited. So allow it
> but also warn user about possible issue.

> Signed-off-by: Ruslan Bilovol <ruslan.bilovol@gmail.com>
> ---
> drivers/net/usb/usbnet.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)

> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index 733f4fe..09dc848 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -382,9 +382,11 @@ int usbnet_change_mtu (struct net_device *net, int new_mtu)
>
> if (new_mtu <= 0)
> return -EINVAL;
> - // no second zero-length packet read wanted after mtu-sized packets
> + /* warn about second zero-length packet read after mtu-sized packets */
> if ((ll_mtu % dev->maxpacket) == 0)
> - return -EDOM;
> + netdev_warn(dev->net, "MTU %d is a multiple of USB wMaxPacketSize (%d),"
> + " consider possible performance degradation\n",

Please do not wrap the kernel messages, it impedes grepping for them.
scripts/checkpatch.pl is aware of this rule.

WBR, Sergei



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