netdev - Re: [PATCH net-next 7/9] devlink: allow registering parameters after the instance

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Message-ID: <Y7+xv6gKaU+Horrk@unreal>
Date:   Thu, 12 Jan 2023 09:07:43 +0200
From:   Leon Romanovsky <leon@...nel.org>
To:     Jacob Keller <jacob.e.keller@...el.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, Jiri Pirko <jiri@...nulli.us>,
        davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
        pabeni@...hat.com
Subject: Re: [PATCH net-next 7/9] devlink: allow registering parameters after
 the instance

On Wed, Jan 11, 2023 at 01:29:03PM -0800, Jacob Keller wrote:
> 
> 
> On 1/11/2023 8:45 AM, Jakub Kicinski wrote:
> > On Wed, 11 Jan 2023 10:32:13 +0100 Jiri Pirko wrote:
> >>>> I'm confused. You want to register objects after instance register?  
> >>>
> >>> +1, I think it's an anti-pattern.  
> >>
> >> Could you elaborate a bit please?
> > 
> > Mixing registering sub-objects before and after the instance is a bit
> > of an anti-pattern. Easy to introduce bugs during reload and reset /
> > error recovery. I thought that's what you were saying as well.
> 
> I was thinking of a case where an object is dynamic and might get added
> based on events occurring after the devlink was registered.
> 
> But the more I think about it the less that makes sense. What events
> would cause a whole subobject to be registerd which we wouldn't already
> know about during initialization of devlink?
> 
> We do need some dynamic support because situations like "add port" will
> add a port and then the ports subresources after the main devlink, but I
> think that is already supported well and we'd add the port sub-resources
> at the same time as the port.
> 
> But thinking more on this, there isn't really another good example since
> we'd register things like health reporters, regions, resources, etc all
> during initialization. Each of these sub objects may have dynamic
> portions (ex: region captures, health events, etc) but the need for the
> object should be known about during init time if its supported by the
> device driver.

As a user, I don't want to see any late dynamic object addition which is
not triggered by me explicitly. As it doesn't make any sense to add
various delays per-vendor/kernel in configuration scripts just because
not everything is ready. Users need predictability, lazy addition of
objects adds chaos instead.

Agree with Jakub, it is anti-pattern.

Thanks