linux-kernel - Re: [PATCH 6/6] pci, acpi: Share ACPI PCI config space accessors.

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Message-ID: <546CC436.4000902@linaro.org>
Date:	Wed, 19 Nov 2014 17:24:22 +0100
From:	Tomasz Nowicki <tomasz.nowicki@...aro.org>
To:	Arnd Bergmann <arnd@...db.de>, linux-arm-kernel@...ts.infradead.org
CC:	catalin.marinas@....com, will.deacon@....com, bhelgaas@...gle.com,
	lorenzo.pieralisi@....com, wangyijing@...wei.com,
	hanjun.guo@...aro.org, Liviu.Dudau@....com, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, rjw@...ysocki.net,
	linaro-acpi@...ts.linaro.org, linux-pci@...r.kernel.org,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH 6/6] pci, acpi: Share ACPI PCI config space accessors.

On 19.11.2014 17:19, Arnd Bergmann wrote:
> On Wednesday 19 November 2014 17:04:51 Tomasz Nowicki wrote:
>> +/*
>> + * raw_pci_read/write - ACPI PCI config space accessors.
>> + *
>> + * ACPI spec defines MMCFG as the way we can access PCI config space,
>> + * so let MMCFG be default (__weak).
>> + *
>> + * If platform needs more fancy stuff, should provides its own implementation.
>> + */
>> +int __weak raw_pci_read(unsigned int domain, unsigned int bus,
>> +                       unsigned int devfn, int reg, int len, u32 *val)
>> +{
>> +       return pci_mmcfg_read(domain, bus, devfn, reg, len, val);
>> +}
>> +
>> +int __weak raw_pci_write(unsigned int domain, unsigned int bus,
>> +                        unsigned int devfn, int reg, int len, u32 val)
>> +{
>> +       return pci_mmcfg_write(domain, bus, devfn, reg, len, val);
>> +}
>> +
>>
>
> I think it would be better to avoid __weak functions here, as they tend
> to be hard to follow when trying to understand the code.
>
> How about using a Kconfig symbol like this:
>
> #ifdef CONFIG_ARCH_RAW_PCI_READWRITE
> int raw_pci_read(unsigned int domain, unsigned int bus, unsigned int devfn,
>                   int reg, int len, u32 *val);
> int raw_pci_write(unsigned int domain, unsigned int bus, unsigned int devfn,
>                    int reg, int len, u32 val);
> #else
> static inline int raw_pci_read(unsigned int domain, unsigned int bus,
> 	                       unsigned int devfn, int reg, int len, u32 *val)
> {
> 	return pci_mmcfg_read(domain, bus, devfn, reg, len, val);
> }
>
> static inline int raw_pci_write(unsigned int domain, unsigned int bus,
>               		                unsigned int devfn, int reg, int len, u32 val)
> {
>         return pci_mmcfg_write(domain, bus, devfn, reg, len, val);
> }
> #endif
>
> Same thing for the weak symbols in patch 5.
>

It makes sense to me, thanks!

Tomasz

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