netdev - Re: [PATCH v4 bpf-next 15/22] xsk: add multi-buffer documentation

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Message-ID: <ZJ3pgau3icByxQxE@boxer>
Date: Thu, 29 Jun 2023 22:28:49 +0200
From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>
CC: Magnus Karlsson <magnus.karlsson@...il.com>, Jakub Kicinski
	<kuba@...nel.org>, <bpf@...r.kernel.org>, <ast@...nel.org>,
	<daniel@...earbox.net>, <andrii@...nel.org>, <netdev@...r.kernel.org>,
	<magnus.karlsson@...el.com>, <bjorn@...nel.org>,
	<tirthendu.sarkar@...el.com>, <simon.horman@...igine.com>
Subject: Re: [PATCH v4 bpf-next 15/22] xsk: add multi-buffer documentation

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?

> 
> -Toke
> 
>