On Thu, Jun 29, 2023 at 10:57:05PM +0200, Toke Høiland-Jørgensen wrote: > Maciej Fijalkowski <maciej.fijalkowski@xxxxxxxxx> writes: > > > On Wed, Jun 28, 2023 at 11:02:06PM +0200, Toke Høiland-Jørgensen wrote: > >> > diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c > >> > index a4270fafdf11..b24244f768e3 100644 > >> > --- a/net/core/netdev-genl.c > >> > +++ b/net/core/netdev-genl.c > >> > @@ -19,6 +19,8 @@ netdev_nl_dev_fill(struct net_device *netdev, struct sk_buff *rsp, > >> > return -EMSGSIZE; > >> > > >> > if (nla_put_u32(rsp, NETDEV_A_DEV_IFINDEX, netdev->ifindex) || > >> > + nla_put_u32(rsp, NETDEV_A_DEV_XDP_ZC_MAX_SEGS, > >> > + netdev->xdp_zc_max_segs) || > >> > >> Should this be omitted if the driver doesn't support zero-copy at all? > > > > This is now set independently when allocing net_device struct, so this can > > be read without issues. Furthermore this value should not be used to find > > out if underlying driver supports ZC or not - let us keep using > > xdp_features for that. > > > > Does it make sense? > > Yes, I agree we shouldn't use this field for that. However, I am not > sure I trust all userspace applications to get that right, so I fear > some will end up looking at the field even when the flag is not set, > which will lead to confused users. So why not just omit the property > entirely when the flag is not set? :) I think that if you would read anything different than default 1 from this field and your driver does not zupport even ZC then your driver is wrong. It's like reporting something via xdp_features and not supporting it. You only overwrite this within your driver *if* you support ZC multi-buffer. OTOH were you referring to omitting putting the u32 to netlink response at all? > > -Toke >
