netdev - Re: [EXTERNAL] Re: [PATCH net-next] octeon_ep: add ndo ops for VFs in PF driver

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Message-ID: <20241112141223.GQ4507@kernel.org>
Date: Tue, 12 Nov 2024 14:12:23 +0000
From: Simon Horman <horms@...nel.org>
To: Shinas Rasheed <srasheed@...vell.com>
Cc: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Haseeb Gani <hgani@...vell.com>,
	Sathesh B Edara <sedara@...vell.com>,
	Vimlesh Kumar <vimleshk@...vell.com>,
	"thaller@...hat.com" <thaller@...hat.com>,
	"wizhao@...hat.com" <wizhao@...hat.com>,
	"kheib@...hat.com" <kheib@...hat.com>,
	"egallen@...hat.com" <egallen@...hat.com>,
	"konguyen@...hat.com" <konguyen@...hat.com>,
	"frank.feng@...axg.com" <frank.feng@...axg.com>,
	Veerasenareddy Burru <vburru@...vell.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Subject: Re: [EXTERNAL] Re: [PATCH net-next] octeon_ep: add ndo ops for VFs
 in PF driver

On Mon, Nov 11, 2024 at 05:29:53AM +0000, Shinas Rasheed wrote:
> Hi Simon,
> 
> On Thu, Nov 07, 2024 at 04:16:37AM -0800, Shinas Rasheed wrote:
> >> These APIs are needed to support applicaitons that use netlink to get VF
> >> information from a PF driver.
> >> 
> >> Signed-off-by: Shinas Rasheed <mailto:srasheed@...vell.com>
> >
> >...
> >
> >> +static int octep_set_vf_vlan(struct net_device *dev, int vf, u16 vlan, u8 qos, __be16 vlan_proto)
> >> +{
> >> +	struct octep_device *oct = netdev_priv(dev);
> >> +
> >> +	dev_err(&oct->pdev->dev, "Setting VF VLAN not supported\n");>
> >> +	return 0;
> >> +}
> >
> >Hi Shinas,
> >
> >Given that the operation is not supported I think it would
> >be more appropriate to return -EOPNOTSUPP. And moreover, given
> >that this is a noop, I think it would be yet more appropriate
> >not to implement it at all and let the core treat it as not supported.
> >
> >Likewise for other NDOs implemented as noops in this patch.
> >
> >...
> 
> I think the problem was for some userspace programs and operators, sometimes returning -EOPNOTSUPP is a no-go. I think the idea was at least if the user saw these messages, they would know to
> set it in some other way, and also not have the operator stop just because setting these values failed. Though I understand that’s counter-intuitive, but sometimes it lets operators work and go ahead. What do you think so?

Hi Shinas,

I think it would be good to provide more detail of such use-cases:
my understanding is that not implementing the operations would
be the go-to solution if they are not supported by the driver.

> 
> Thanks for the comments!