Hi!
I am testing to configure the e1000 acceleration features via ethtool API
and have run into difficulties.
in e1000/e1000_main.c the following sequence is found:
if (hw->mac_type >= e1000_82543) {
netdev->hw_features = NETIF_F_SG |
NETIF_F_HW_CSUM |
NETIF_F_HW_VLAN_RX;
netdev->features = NETIF_F_HW_VLAN_TX |
NETIF_F_HW_VLAN_FILTER;
}
if ((hw->mac_type >= e1000_82544) &&
(hw->mac_type != e1000_82547))
netdev->hw_features |= NETIF_F_TSO;
netdev->priv_flags |= IFF_SUPP_NOFCS;
netdev->features |= netdev->hw_features;
netdev->hw_features |= NETIF_F_RXCSUM;
netdev->hw_features |= NETIF_F_RXFCS;
If my analysis is correct, the
netdev->features |= netdev->hw_features;
at this point makes sure that netdev->features has all features
activated that are supported via netdev->hw_features.
In net/core/ethtool:__ethtool_set_flags() however:
/* allow changing only bits set in hw_features */
changed = (features ^ dev->features) & ETH_ALL_FEATURES;
if (changed & ~dev->hw_features)
return (changed & dev->hw_features) ? -EINVAL : -EOPNOTSUPP;
This means that trying to change those features that are not listed
as hw_features fails. In my case I tried do disable NETIF_F_HW_VLAN_TX
and NETIF_F_HW_VLAN_RX via ethtool API and got an EINVAL as
NETIF_F_HW_VLAN_TX is not defined in hw_features.
This is easily fixed by adding NETIF_F_HW_VLAN_TX and NETIF_F_HW_VLAN_FILTER
to netdev->hw_features as well (I can easily supply a patch) but
wanted to make sure that this is the correct way to fix this issue.
Note: e1000e/netdev.c also has another suspective code:
netdev->hw_features = netdev->features;
...
if (adapter->flags & FLAG_HAS_HW_VLAN_FILTER)
netdev->features |= NETIF_F_HW_VLAN_FILTER;
meaning that NETIF_F_HW_VLAN_FILTER could be set in features without
being announced in hw_features.
I have not checked out the other drivers discussed on this list (as I
do not have respective hardware). My goal is to use the ethtool API
consistently wrt other drivers like PowerPC/gianfar so implicit
knowledge like "it is sufficient to modify NETIF_F_HW_VLAN_RX to
magically also disable NETIF_F_HW_VLAN_TX" doesn't seem to be the
way to go.
Best regards,
Lutz
--
Dr.-Ing. Lutz Jänicke
CTO
Innominate Security Technologies AG /protecting industrial networks/
tel: +49.30.921028-200
fax: +49.30.921028-020
Rudower Chaussee 13
D-12489 Berlin, Germany
www.innominate.com
Register Court: AG Charlottenburg, HR B 81603
Management Board: Dirk Seewald
Chairman of the Supervisory Board: Christoph Leifer
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