linux-kernel - Re: [PATCH v5 1/2] PCI support added to ARC

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Date:	Thu, 14 Jan 2016 11:22 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>
Cc:	Joao Pinto <Joao.Pinto@...opsys.com>,
	"helgaas@...nel.org" <helgaas@...nel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-snps-arc@...ts.infradead.org" 
	<linux-snps-arc@...ts.infradead.org>,
	"CARLOS.PALMINHA@...opsys.com" <CARLOS.PALMINHA@...opsys.com>,
	"Alexey.Brodkin@...opsys.com" <Alexey.Brodkin@...opsys.com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>
Subject: Re: [PATCH v5 1/2] PCI support added to ARC

On Thursday 14 January 2016 05:26:58 Vineet Gupta wrote:
> > +/*
> > + * We don't have to worry about legacy ISA devices, so nothing to do here
> > + */
> > +resource_size_t pcibios_align_resource(void *data, const struct resource *res,
> > +                             resource_size_t size, resource_size_t align)
> > +{
> > +     return res->start;
> > +}
> 
> Doesn't this have to be EXPORT_SYMBOL_xxx as well given that the call
> (setup-res.c) can build as module ?

I only see a caller in drivers/pci/setup-res.c, and that is never part of a
loadable module.

> > +
> > +void pcibios_fixup_bus(struct pci_bus *bus)
> > +{
> > +}
> > +EXPORT_SYMBOL(pcibios_fixup_bus);
> 
> EXPORT_SYMBOL_GPL ?
> 
> As a seperate enhancement, it would be nicer if these 2 functions are defined weak
> in common code. That would make basic PCI support almost arch independent !

I agree, that would be ideal. An easy way to do this would be to add
them as __weak functions in drivers/pci/, similar to how we handle
a lot of the other pcibios_* functions.

A somewhat nicer method would be to have callback pointers in struct
pci_host_bridge, and call those when they are non-NULL so we can
remove the global pcibios_* functions from the API. That would also
bring us a big step closer to having PCI support itself as a loadable
module, and it would better reflect that those functions are really
host bridge specific rather than architecture specific. When you use
the same host bridge on multiple architectures, you typically have
the same requirements for hacks in there, but each architectures may
need to support multiple host bridges with different requirements.

	Arnd