linux-kernel - Re: [PATCH] acpi, property: Export acpi_dev_prop_read

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Date:	Wed, 5 Aug 2015 16:17:21 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	David Daney <ddaney.cavm@...il.com>,
	Tomasz Nowicki <tomasz.nowicki@...aro.org>,
	<linux-kernel@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	Robert Richter <rrichter@...ium.com>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH] acpi, property: Export acpi_dev_prop_read_single call.

On 08/05/2015 04:23 PM, Rafael J. Wysocki wrote:
> On Wednesday, August 05, 2015 01:14:49 PM David Daney wrote:
>> On 08/05/2015 10:26 AM, David Daney wrote:
>>> On 08/05/2015 06:43 AM, Tomasz Nowicki wrote:
>>>> On 05.08.2015 15:48, Rafael J. Wysocki wrote:
>>>>> On Tuesday, August 04, 2015 04:01:59 PM David Daney wrote:
>>>>>> From: Tomasz Nowicki <tomasz.nowicki@...aro.org>
>>>>>>
>>>>>> Fixes the following build error when building drivers as modules:
>>>>>>
>>>>>>    ERROR: "acpi_dev_prop_read_single" [drivers/net/phy/mdio-octeon.ko]
>>>>>> undefined!
>>>>>>    ERROR: "acpi_dev_prop_read_single"
>>>>>> [drivers/net/ethernet/cavium/thunder/thunder_bgx.ko] undefined!
>>>>>
>>>>> Can you please tell me why the drivers in question use that function
>>>>> directly, although they aren't supposed to?
>>>>>
>>>>> Clearly, their authors had not tried to build them as modules or they
>>>>> would have noticed the problem at the development stage already.
>>>>>
>>>>> What would be wrong with using the generic device properties API
>>>>> instead?
>>>>>
>>>> Yes, you are right. We should use:
>>>> int device_property_read_u64_array(struct device *dev, const char
>>>> *propname, u64 *val, size_t nval);
>>>>
>>>
>>> Thanks all, for the review and suggestions.  We we try the suggested
>>> approach and see how it goes...
>>>
>>
>> Actually I don't think device_property_read_u64_array() will work.
>>
>> We are traversing a reference to a different acpi_device via
>> acpi_dev_get_property_reference(),
>
> Why?

Network device has a "phy-handle" (traversed with 
acpi_dev_get_property_reference()), and we want to get some properties 
of that phy.

I could turn the question around to you:  Why export 
acpi_dev_get_property_reference()?  If there is a reason to export that, 
then you should let people use the result.


>
>> so there is no struct device *
>> available for a call to device_property_read_u64_array().  This looks
>> like a deficiency in the device_property_* framework, so for the time
>> being I guess we will call acpi_dev_get_property(), which is exported,
>> and decode the thing in the driver.
>
> Please don't.
>
> I'd like to understand what's missing.
>
> Thanks,
> Rafael
>

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