RE: [PATCH 1/2] cdx: Enable COMPILE_TEST

[Gangurde, Abhijit]

> > On Thu, Dec 07, 2023 at 10:31:26AM -0600, Rob Herring wrote:
> > > There is no reason CDX needs to depend on ARM64 other than limiting
> > > visibility. So let's also enable building with COMPILE_TEST.
> > >
> > > The CONFIG_OF dependency is redundant as ARM64 always enables it and
> all
> > > the DT functions have empty stubs.
> > >
> > > Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
> > > ---
> > >  drivers/cdx/Kconfig | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/cdx/Kconfig b/drivers/cdx/Kconfig
> > > index a08958485e31..7cdb7c414453 100644
> > > --- a/drivers/cdx/Kconfig
> > > +++ b/drivers/cdx/Kconfig
> > > @@ -7,7 +7,7 @@
> > >
> > >  config CDX_BUS
> > >  	bool "CDX Bus driver"
> > > -	depends on OF && ARM64
> > > +	depends on ARM64 || COMPILE_TEST
> >
> > Ok, good start, now we need to turn this into a module, what's keeping
> > it from being able to be built as a tristate?
> 
> To answer my own question, the following errors:
> 
> ERROR: modpost: missing MODULE_LICENSE() in drivers/cdx/cdx.o
> ERROR: modpost: "iommu_device_unuse_default_domain"
> [drivers/cdx/cdx.ko] undefined!
> ERROR: modpost: "iommu_device_use_default_domain" [drivers/cdx/cdx.ko]
> undefined!
> 
> Would be great for someone to fix this up...

I did look at this code. There are 2 issues here for it to be a module.
1. There are many symbols in iommu, msi and other module which are not exported.
Most of other busses like amba, fslmc, pci are bool only.
2. As of now, iommu has static list on bus types (static struct bus_type * const iommu_buses[])
 which is initializes the notifier at init time. So, if we change cdx bus to be a module
cdx devices would miss these mappings.

Thanks,
Abhijit