netdev - Re: Use of ENOTSUPP in drivers?

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Message-ID: <1408352.Qio0cxKTUV@lenovo>
Date:	Sun, 12 Jan 2014 13:19:36 -0800
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Ben Hutchings <bhutchings@...arflare.com>
Cc:	Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org
Subject: Re: Use of ENOTSUPP in drivers?

Le dimanche 12 janvier 2014, 20:47:02 Ben Hutchings a écrit :
> On Sun, 2014-01-12 at 19:57 +0100, Sabrina Dubroca wrote:
> > Thu, 2 Jan 2014 12:01:31 +0000, Ben Hutchings wrote:
> > > Never return error code ENOTSUPP; it's *not* the same thing as ENOTSUP
> > > in userland and is not part of the userland ABI.  I would use EINVAL
> > > here.
> > 
> > I've found a few ethernet drivers that return -ENOTSUPP in various
> > functions. In particular, some ethtool functions or ioctl's.
> > Ben's message makes me think that the ethtool functions and ioctl's
> > should be modified.
> > 
> > There are other occurences, mostly in functions related to device
> > initialization. I didn't manage to track down exactly from where some
> > of them are called, and I don't know if ENOTSUPP is okay in these.
> > 
> > I've included the complete list of occurences (based on net-next) from
> > drivers/net/ethernet in patch form at the end, if that's more
> > convenient than the file/function list. This is not meant to be
> > applied.
> > 
> > 
> > Do these (or part of them) need to be patched? Or is there something
> > I'm missing?
> 
> [...]
> 
> I believe they should all be patched.  According to
> include/linux/errno.h, ENOTSUPP is meant for use in the NFSv3 code only.
> (But it's apparently erroneously used *all over* the tree, not just in
> net drivers!)

Most other drivers use -EOPNOTSUPP, which is arguably as bad as -ENOTSUPP, 
since the comment about it says:

* Operation not supported on transport endpoint *

But at least changing -ENOTSUPP to -EOPNOTSUPP until something better which is 
not protocol/endpoint specific is agreed on might be better for consistency?
-- 
Florian
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