| Message ID | 1430992159-27783-1-git-send-email-ruslan.bilovol@gmail.com |
|---|---|
| State | Changes Requested, archived |
| Delegated to: | David Miller |
| Headers | show |
On Thu, 2015-05-07 at 12:49 +0300, 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. We have reports about devices reacting badly to ZLPs. Unless you have a compelling reasons for this change I have to reject it. Regards Oliver NACK -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Oliver, On Thu, May 7, 2015 at 1:11 PM, Oliver Neukum <oneukum@suse.de> wrote: > On Thu, 2015-05-07 at 12:49 +0300, 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. > > We have reports about devices reacting badly to ZLPs. > Unless you have a compelling reasons for this change > I have to reject it. What devices do you mean here: USB network adapters or USB host controllers? If it's just network adapters, then we can create some kind of quirk handling for them and do not disable this functionality just because some buggy device can't work with it. My device works fine with ZLPs so I want to use this particular MTU under Linux like I do it under other operation systems. Regards, Ruslan > > Regards > Oliver > > NACK > -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, 2015-05-07 at 13:51 +0300, Ruslan Bilovol wrote: > Hi Oliver, > > On Thu, May 7, 2015 at 1:11 PM, Oliver Neukum <oneukum@suse.de> wrote: > > On Thu, 2015-05-07 at 12:49 +0300, 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. > > > > We have reports about devices reacting badly to ZLPs. > > Unless you have a compelling reasons for this change > > I have to reject it. > > What devices do you mean here: USB network adapters or USB host controllers? The network adapters > If it's just network adapters, then we can create some kind of quirk handling > for them and do not disable this functionality just because some buggy device > can't work with it. No. They are too many. > My device works fine with ZLPs so I want to use this particular MTU under Linux > like I do it under other operation systems. We can have a white list, but the general case is just too dangerous. Sorry Oliver -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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", + ll_mtu, dev->maxpacket); net->mtu = new_mtu; dev->hard_mtu = net->mtu + net->hard_header_len;
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(-)