Re: [usb-storage] Re: [PATCH v4 12/12] RFC: watchdog: export core symbols in WATCHDOG_CORE namespace

[Jessica Yu]

+++ Arnd Bergmann [05/09/19 12:52 +0200]:
> On Thu, Sep 5, 2019 at 12:41 PM Jessica Yu <jeyu@xxxxxxxxxx> wrote:
> > +++ Matthew Dharm [04/09/19 09:16 -0700]:
> > >On Wed, Sep 4, 2019 at 5:12 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> > >HOWEVER, I have one question:  If these patches are included, and
> > >someone wants to introduce a bit of code which needs to use two
> > >symbols from different namespaces but with the same name, can that be
> > >done?  That is, if driver A has symbol 'foo' and driver B has symbol
> > >'foo' (both in their respective namespaces), and driver C wants to use
> > >A.foo and B.foo, can that be supported?
> >
> > As of now, we currently don't support this - modpost will warn if a
> > symbol is exported more than once (across modules + vmlinux), and the
> > module loader currently assumes exported symbol names are unique.  Do
> > you have a concrete use case? If there is a strong need for this, I
> > don't think it'd be too hard to implement.
>
> I think what would prevent this from working in general is that having
> two modules with the same exported symbol in different namespaces
> won't link if you try to build both modules into the kernel itself.
>
>      Arnd

Ah yeah, you are right. I only tried building an identically named
exported symbol in a module and in the kernel, and there I got away
with a modpost warning. But this breaks when building the module into
the kernel, so I guess this is out of the question.

Thanks,

Jessica