netdev - Re: [PATCH net-next] gve: Correctly report software timestamping capabilities

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Date: Tue, 9 Apr 2024 17:28:38 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: John Fraker <jfraker@...gle.com>, netdev@...r.kernel.org, Praveen
 Kaligineedi <pkaligineedi@...gle.com>, Harshitha Ramamurthy
 <hramamurthy@...gle.com>, Shailend Chand <shailend@...gle.com>, Willem de
 Bruijn <willemb@...gle.com>, "David S. Miller" <davem@...emloft.net>,
 Junfeng Guo <junfeng.guo@...el.com>, Ziwei Xiao <ziweixiao@...gle.com>,
 Jeroen de Borst <jeroendb@...gle.com>, linux-kernel@...r.kernel.org,
 kory.maincent@...tlin.com, andrew@...n.ch, richardcochran@...il.com
Subject: Re: [PATCH net-next] gve: Correctly report software timestamping
 capabilities

On Tue, 09 Apr 2024 10:29:55 -0400 Willem de Bruijn wrote:
> This device calls skb_tx_timestamp in its ndo_start_xmit: the
> prerequisite for SOF_TIMESTAMPING_TX_SOFTWARE.
> 
> All devices support SOF_TIMESTAMPING_RX_SOFTWARE by virtue of
> net_timestamp_check being called in the device independent code.
> 
> To ethtool timestamping maintainers: It's quite unnecessary to have
> each device advertise SOF_TIMESTAMPING_RX_SOFTWARE |
> SOF_TIMESTAMPING_SOFTWARE. In __ethtool_get_ts_info we could just
> always add those flags to the result from the callees.
> 
>         if (phy_has_tsinfo(phydev))
>                 return phy_ts_info(phydev, info);
>         if (ops->get_ts_info)
>                 return ops->get_ts_info(dev, info);
> 
>         info->so_timestamping = SOF_TIMESTAMPING_RX_SOFTWARE |
>                                 SOF_TIMESTAMPING_SOFTWARE;

My gut tells me we force drivers to set the ethtool op because
while at it they will probably also implement tx stamping.

Even more unhelpful point I'll risk making is that we could 
add a test and make people who submit new drivers run it :)