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

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Date:	Thu, 14 Jan 2016 10:54:19 +0000
From:	Joao Pinto <Joao.Pinto@...opsys.com>
To:	Vineet Gupta <Vineet.Gupta1@...opsys.com>,
	Arnd Bergmann <arnd@...db.de>
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 10:51 AM, Vineet Gupta wrote:
> On Thursday 14 January 2016 04:12 PM, Joao Pinto wrote:
>> 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?
> 
> 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.
> 
> And then as a follow up to make them weak (and hence eliminate the scattered
> definitions all over). And then add as callbacks as suggested by Arnd.
> 

Ok, I'll removed the EXPORT_SYMBOL and submit a new patch version.
Thanks for your comments!

> Thx,
> -Vineet
> 
>>
>>> 	Arnd
>>>
>> Thanks
>> Joao
>>
>>
>>
> 
>