netdev - Re: [PATCH net-next V2] net: ks8851: Fix mixed module/builtin build

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Date:   Sat, 16 Jan 2021 21:39:45 +0100
From:   Lukas Wunner <lukas@...ner.de>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Marek Vasut <marex@...x.de>, Networking <netdev@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net-next V2] net: ks8851: Fix mixed module/builtin build

On Sat, Jan 16, 2021 at 08:26:22PM +0100, Arnd Bergmann wrote:
> On Sat, Jan 16, 2021 at 6:56 PM Marek Vasut <marex@...x.de> wrote:
> > On 1/16/21 6:04 PM, Arnd Bergmann wrote:
> > > On Sat, Jan 16, 2021 at 5:48 PM Marek Vasut <marex@...x.de> wrote:
> >
> > > I don't really like this version, as it does not actually solve the problem of
> > > linking the same object file into both vmlinux and a loadable module, which
> > > can have all kinds of side-effects besides that link failure you saw.
> > >
> > > If you want to avoid exporting all those symbols, a simpler hack would
> > > be to '#include "ks8851_common.c" from each of the two files, which
> > > then always duplicates the contents (even when both are built-in), but
> > > at least builds the file the correct way.
> >
> > That's the same as V1, isn't it ?
> 
> Ah, I had not actually looked at the original submission, but yes, that
> was slightly better than v2, provided you make all symbols static to
> avoid the new link error.
> 
> I still think that having three modules and exporting the symbols from
> the common part as Heiner Kallweit suggested would be the best
> way to do it.

FWIW I'd prefer V1 (the #include approach) as it allows going back to
using static inlines for register access.  That's what we had before
7a552c850c45.

It seems unlikely that a system uses both, the parallel *and* the SPI
variant of the ks8851.  So the additional memory necessary because of
code duplication wouldn't matter in practice.

Thanks,

Lukas