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

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Date:	Thu, 14 Jan 2016 12:59:56 +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 10:51:32 Vineet Gupta wrote:
> >>
> >> 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.
> > Since we will be constantly improving the driver and the core itself, I suggest
> > that this functions be made __weak and in an update we can turn it struct
> > pointers just like Arnd suggested. Is this good for you?
> 
> There is no point in making it weak, w/o a fallback version in generic code. For
> this series, I suggest you just remove the straggler EXPORT_SYMBOL and respin.
> 

To clarify: I don't particularly like __weak functions anywhere, but they
are already common in drivers/pci, so we can add a couple more to reach
the goal of removing all architecture specific code.

However, there should never be a reason to add a __weak function in
arch code that gets overridden by common code, that would be very confusing
and not helpful.

	Arnd