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

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Date:	Thu, 14 Jan 2016 10:42:08 +0000
From:	Joao Pinto <Joao.Pinto@...opsys.com>
To:	Arnd Bergmann <arnd@...db.de>,
	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

Hi,

On 1/14/2016 10:22 AM, Arnd Bergmann wrote:
> 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.

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?

> 
> 	Arnd
> 

Thanks
Joao