linux-kernel - Re: [PATCH v3] Add MO(mod objs) variable to process ext modules with subdirs

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Date: Thu, 11 Apr 2024 20:50:10 +0000
From: "Daniel Walker (danielwa)" <danielwa@...co.com>
To: Nicolas Schier <nicolas@...sle.eu>
CC: Nicolas Schier <n.schier@....de>,
        "Valerii Chernous -X (vchernou -
 GLOBALLOGIC INC at Cisco)" <vchernou@...co.com>,
        Masahiro Yamada
	<masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "xe-linux-external(mailer list)" <xe-linux-external@...co.com>,
        Jonathan
 Corbet <corbet@....net>,
        "linux-kbuild@...r.kernel.org"
	<linux-kbuild@...r.kernel.org>,
        "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] Add MO(mod objs) variable to process ext modules with
 subdirs

On Thu, Apr 11, 2024 at 09:25:35PM +0200, Nicolas Schier wrote:
> On Thu, Apr 11, 2024 at 05:27:42PM +0000 Daniel Walker (danielwa) wrote:
> > On Thu, Apr 11, 2024 at 01:38:20PM +0200, Nicolas Schier wrote:
> > > Hi Valerii,
> > > 
> > > thanks for your patch.  I know several non-upstream kernel developers
> > > that would like to see support for out-of-source builds of external
> > > kmods (and we developed several work-arounds at AVM as well); but please
> > > be aware that patches that don't fix or enhance the in-tree kernel/kmod
> > > build but only add feature for out-of-tree stuff, are rarely accepted.
> 
> "out-of-tree stuff" was meant to be "out-of-tree kernel modules".  "Rarely" was
> chosen in explicit contrast to "never", but to hint on my personal expectation
> regarding the probability of acceptance.
> 
> > If that were true we would not have driver/uio/ for example. It seems like
> > Cisco and NVM should work together produce a solution.
> > 
> > You could run into this issue even with entirely in tree modules. For example,
> > we may have a v6.6 kernel but we need some modules from v5.15 for some incompatibility
> > reason in v6.6. Then we may build the v5.15 modules as out of tree modules
> > against the v6.6 kernel.
 
All problems should be fixed or worked around. One bit of code maybe isn't
the best choice or maybe another is, but not fixing or working around the
problem is not really an option.

> If your in-tree module in question does compile and run properly in v5.15 and
> in v6.6: why don't you just compile it in-tree in v6.6?  Which driver/module do
> you refer to?

I believe it was this driver drivers/crypto/marvell/octeontx2 . I don't recall
every aspect of the issues but it has to do with what Marvell supported in their
SDK and the exact hardware we were using and the bootloader we had on the
product.

> > You also have just normal developers making kernel modules which always start as
> > out of tree modules before they are upstreamed. Those modules could be any level
> > of complexity.
> 
> I do not agree, but there is no need to convince me as I am not in the position
> to decide between acceptance or denial.  I just thought it might be fair to
> warn that I do not expect acceptance.

I think it's incorrect, unhealthy even, to look at it that way. If your using
Linux to make a product and you have an issue, it should be consider as a real
issue. Not something maintainer can just discard. Unless the maintainer has
a suggestion to do what is needed or different code to do it.

Daniel