linux-kernel - Re: [PATCH V2 2/4] ACPI/scan: Clean up acpi_check

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Message-ID: <55DD1DB7.1020203@amd.com>
Date:	Wed, 26 Aug 2015 09:00:23 +0700
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	<bhelgaas@...gle.com>, <lenb@...nel.org>,
	<catalin.marinas@....com>, <will.deacon@....com>,
	<hanjun.guo@...aro.org>, <linux-acpi@...r.kernel.org>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH V2 2/4] ACPI/scan: Clean up acpi_check_dma

Hi Rafael,

On 8/26/15 06:48, Rafael J. Wysocki wrote:

>[...]
> On Wednesday, August 26, 2015 12:33:27 AM Suravee Suthikulpanit wrote:
>> diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
>> index b9657af..55cf916 100644
>> --- a/drivers/acpi/glue.c
>> +++ b/drivers/acpi/glue.c
>> @@ -168,7 +168,7 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
>>   	struct list_head *physnode_list;
>>   	unsigned int node_id;
>>   	int retval = -EINVAL;
>> -	bool coherent;
>> +	int coherent;
>
> enum, anyone?  With clearly defined values?

Originally I had defined

enum acpi_dma_coherency {
	ACPI_DMA_NON_COHERENT,
	ACPI_DMA_COHERENT,
	APCI_DMA_NOT_SUPPORTED = -1,
};

Although, this would need to be defined in the include/linux/acpi.h, and 
will be used also for #ifndef CONFIG_ACPI code to return errors. I was 
not sure if this would be too much. If this is preferred, I'll add this 
back in.

>>
>>   	if (has_acpi_companion(dev)) {
>>   		if (acpi_dev) {
>> @@ -225,7 +225,8 @@ int acpi_bind_one(struct device *dev, struct acpi_device *acpi_dev)
>>   	if (!has_acpi_companion(dev))
>>   		ACPI_COMPANION_SET(dev, acpi_dev);
>>
>> -	if (acpi_check_dma(acpi_dev, &coherent))
>> +	coherent = acpi_check_dma_coherency(acpi_dev);
>> +	if (coherent != -1)
>
> Like here I'm not sure why -1 is special?

It's just another value to communicate that DMA is not supported. :)

Thanks,
Suravee
>
>>   		arch_setup_dma_ops(dev, 0, 0, NULL, coherent);
>>
>>   	acpi_physnode_link_name(physical_node_name, node_id);
>
> Thanks,
> Rafael
>
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