netdev - Re: [RFC] fwnode: change the return type of mac address helpers

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Message-ID: <20211006104911.17779805@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 6 Oct 2021 10:49:11 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Shannon Nelson <snelson@...sando.io>
Cc:     Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org,
        gregkh@...uxfoundation.org, rafael@...nel.org,
        saravanak@...gle.com, mw@...ihalf.com, jeremy.linton@....com
Subject: Re: [RFC] fwnode: change the return type of mac address helpers

On Wed, 6 Oct 2021 09:55:59 -0700 Shannon Nelson wrote:
> >>> -	if (!device_get_ethdev_addr(dev, ndev))
> >>> +	if (device_get_ethdev_addr(dev, ndev))
> >>>   		eth_hw_addr_random(ndev);  
> >> That is going to be interesting for out of tree drivers.  
> > Indeed :(  But I think it's worth it - I thought it's only device tree
> > that has the usual errno return code but inside eth.c there are also
> > helpers for platform and nvmem mac retrieval which also return errno.  
> 
> As the maintainer of an out-of-tree driver, this kind of change with 
> little warning really can ruin my day.
> 
> I understand that as Linux kernel developers we really can't spend much 
> time coddling the outer fringe, but we can at least give them hints.  
> Changing the sense of the non-zero return from good to bad in several 
> functions without something else that the compiler can warn on 
> needlessly sets up time bombs for the unsuspecting.  Can we find a way 
> to break their compile rather than surprise them with a broken runtime?

I also changed the arguments in v2, so OOT will no longer silently
break (not that it was the main motivation ;))