linux-kernel - Re: [PATCH v2 1/2] net: make driver settling time configurable

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Date: Fri, 9 Feb 2024 23:11:53 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Jakub Kicinski <kuba@...nel.org>
Cc: David Ventura <david@...idv.dev>, Jonathan Corbet <corbet@....net>,
	"David S. Miller" <davem@...emloft.net>,
	David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Randy Dunlap <rdunlap@...radead.org>,
	Xiongwei Song <xiongwei.song@...driver.com>,
	"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>,
	"open list:NETWORKING [IPv4/IPv6]" <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] net: make driver settling time configurable

On Fri, Feb 09, 2024 at 01:59:44PM -0800, Jakub Kicinski wrote:
> On Thu,  8 Feb 2024 10:52:29 +0100 David Ventura wrote:
> > During IP auto configuration, some drivers apparently need to wait a
> > certain length of time to settle; as this is not true for all drivers,
> > make this length of time configurable.
> 
> Please CC folks who gave you feedback, Andrew's is missing.
> 
> Andrew, what do you think about just removing the wait?
> Or decreasing it to 1ms?
> It feels a little wasteful to be adding uAPI for something
> which as you said is likely papering over ancient bugs. We'll 
> fix the bugs which are still around and the uAPI will stay 
> forever :(

My guess is, the broken drivers are doing setup stuff after they call
netdev_register().

Reducing it to 1ms will probably continue to hide such bugs. So we
could just go with that, and probably not see any regressions. Or we
can decide we really do want to know about broken drivers, and just
remove the delay.

Either way, we don't need a new uAPI.

David, is 1ms too long for you? If we do take the delay out, you are
going to receive some of the flack from regression reports.

      Andrew