linux-kernel - Re: [V4 PATCH 3/6] pci: Generic function for setting up PCI device DMA coherency

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Date:	Wed, 20 May 2015 07:00:25 -0500
From:	Suravee Suthikulanit <suravee.suthikulpanit@....com>
To:	Catalin Marinas <catalin.marinas@....com>,
	Arnd Bergmann <arnd@...db.de>
CC:	<linux-arm-kernel@...ts.infradead.org>,
	<linaro-acpi@...ts.linaro.org>, <will.deacon@....com>,
	<herbert@...dor.apana.org.au>, <al.stone@...aro.org>,
	<linux-acpi@...r.kernel.org>,
	Murali Karicheri <m-karicheri2@...com>, <msalter@...hat.com>,
	<grant.likely@...aro.org>, <hanjun.guo@...aro.org>,
	<thomas.lendacky@....com>, Rob Herring <robh+dt@...nel.org>,
	<bhelgaas@...gle.com>, <netdev@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	<linux-kernel@...r.kernel.org>, <leo.duran@....com>,
	<linux-crypto@...r.kernel.org>, <lenb@...nel.org>,
	David Woodhouse <dwmw2@...radead.org>, <davem@...emloft.net>
Subject: Re: [V4 PATCH 3/6] pci: Generic function for setting up PCI device
 DMA coherency

On 5/20/2015 4:34 AM, Catalin Marinas wrote:
> On Wed, May 20, 2015 at 11:27:54AM +0200, Arnd Bergmann wrote:
>> On Wednesday 20 May 2015 10:24:15 Catalin Marinas wrote:
>>> On Sat, May 16, 2015 at 01:59:00AM +0200, Rafael J. Wysocki wrote:
>>>> On Friday, May 15, 2015 04:23:11 PM Suravee Suthikulpanit wrote:
>>>>> +/**
>>>>> + * pci_dma_configure - Setup DMA configuration
>>>>> + * @pci_dev: ptr to pci_dev struct of the PCI device
>>>>> + *
>>>>> + * Function to update PCI devices's DMA configuration using the same
>>>>> + * info from the OF node or ACPI node of host bridge's parent (if any).
>>>>> + */
>>>>> +static void pci_dma_configure(struct pci_dev *pci_dev)
>>>>> +{
>>>>> +   struct device *dev = &pci_dev->dev;
>>>>> +   struct device *bridge = pci_get_host_bridge_device(pci_dev);
>>>>> +   struct device *host = bridge->parent;
>>>>> +   struct acpi_device *adev;
>>>>> +
>>>>> +   if (!host)
>>>>> +           return;
>>>>> +
>>>>> +   if (acpi_disabled) {
>>>>> +           of_dma_configure(dev, host->of_node);
>>>>
>>>> I'd rather do
>>>>
>>>>        if (IS_ENABLED(CONFIG_OF) && host->of_node) {
>>>>                of_dma_configure(dev, host->of_node);
>>>
>>> Nitpick: do we need the CONFIG_OF check? If disabled, I don't think
>>> anyone would set host->of_node.
>>
>> If of_dma_configure() is defined in a file that is built conditionally
>> based on CONFIG_OF, you need it.
>
> We have a dummy of_dma_configure() already when !CONFIG_OF, otherwise
> we would need #ifndef here. I already replied, I think for other
> architectures we need this check to avoid a useless host->of_node test.
>

It seems that there are several places that have similar check. Would it 
be good to convert this into a macro? Something like:

#define OF_NODE_ENABLED(dev)	(IS_ENABLED(CONFIG_OF) && dev->of_node)

Thanks all for the review feedback.

Suravee

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