linux-kernel - Re: [PATCH] ACPI / property: Export a couple of symbols.

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Date:	Thu, 17 Mar 2016 13:21:54 -0700
From:	David Daney <ddaney.cavm@...il.com>
To:	"Rafael J. Wysocki" <rafael@...nel.org>
CC:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <lenb@...nel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Robert Richter <rrichter@...ium.com>,
	Tomasz Nowicki <tn@...ihalf.com>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH] ACPI / property: Export a couple of symbols.

On 03/17/2016 06:00 AM, Rafael J. Wysocki wrote:
> On Thu, Mar 17, 2016 at 9:09 AM, Mika Westerberg
> <mika.westerberg@...ux.intel.com> wrote:
>> On Wed, Mar 16, 2016 at 05:23:19PM -0700, David Daney wrote:
>>> From: David Daney <david.daney@...ium.com>
>>>
>>> The acpi_dev_prop_read() and acpi_dev_prop_read_single() can be called
>>> by drivers.  Add EXPORT_SYMBOL_GPL to them to allow use by modular
>>> drivers.  This makes them consistent with acpi_dev_get_property() and
>>> acpi_node_get_property_reference() which are already exported.
>>>
>>> Signed-off-by: David Daney <david.daney@...ium.com>
>>> ---
>>> FWIW: We hope to submit soon Cavium Thunder networking patches that
>>> fail under modular builds without these exports.
>>
>> You should not be using these functions directly in drivers.
>
> That's exactly my point.
>

OK, for the sake of argument I will concede that my particular use of 
acpi_dev_prop_read_single() is incorrect.

Let me ask you this:

What is the point of the code in drivers/acpi/property.c?

acpi_dev_prop_read() and acpi_dev_prop_read_single() are not used 
anywhere that I can see in the kernel, would you accept a patch to 
remove them?

But from a philosophical point of view, what is the underlying problem 
of having drivers extract property information from the ACPI tables 
corresponding to the devices they control.

Specifically, I am trying to understand how to port drivers that 
currently successfully use OF device tree so that they are usable in 
systems with ACPI based firmware.

Thanks in advance,
David Daney