linux-kernel - Re: [PATCH RESEND 1/3] PCI: Add fwnode_handle to pci

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Date:	Wed, 3 Feb 2016 18:57:23 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Bjorn Helgaas <helgaas@...nel.org>,
	Jake Oshins <jakeo@...rosoft.com>
Cc:	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	KY Srinivasan <kys@...rosoft.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH RESEND 1/3] PCI: Add fwnode_handle to pci_sysdata

On 03/02/16 18:51, Bjorn Helgaas wrote:
> On Wed, Feb 03, 2016 at 06:32:20PM +0000, Jake Oshins wrote:
>>> -----Original Message-----
>>> From: Bjorn Helgaas [mailto:helgaas@...nel.org]
>>> Sent: Wednesday, February 3, 2016 10:25 AM
>>> To: Jake Oshins <jakeo@...rosoft.com>
>>> Cc: gregkh@...uxfoundation.org; KY Srinivasan <kys@...rosoft.com>; linux-
>>> kernel@...r.kernel.org; devel@...uxdriverproject.org; Haiyang Zhang
>>> <haiyangz@...rosoft.com>; marc.zyngier@....com;
>>> bhelgaas@...gle.com; linux-pci@...r.kernel.org
>>> Subject: Re: [PATCH RESEND 1/3] PCI: Add fwnode_handle to pci_sysdata
>>>
>>> Hi Jake,
>>>
>>> On Tue, Feb 02, 2016 at 05:41:41PM +0000, jakeo@...rosoft.com wrote:
> 
>>>> diff --git a/include/linux/pci.h b/include/linux/pci.h index
>>>> 27df4a6..cd05a8e 100644
>>>> --- a/include/linux/pci.h
>>>> +++ b/include/linux/pci.h
>>>> @@ -1515,6 +1515,10 @@ static inline int pci_get_new_domain_nr(void) {
>>>> return -ENOSYS; }
>>>>
>>>>  #include <asm/pci.h>
>>>>
>>>> +#ifndef pci_root_bus_fwnode
>>>> +#define pci_root_bus_fwnode(bus)	((void)(bus), NULL)
>>>
>>> Huh, interesting.  This is new for me; I guess the idea is that we at least
>>> evaluate "bus" even when pci_root_bus_fwnode isn't defined, so the
>>> compiler can catch egregious errors?
>>>
>>
>> This was a suggestion by Mark Zyngier.  It made the non-x86 architectures build benignly.  If you'd like it done differently, I'm open to suggestion.

I don't remember suggesting the use of the comma operator, but just to
check that pci_root_bus_fwnode wasn't previously defined.

> Something like "#define pci_root_bus_fwnode(bus) NULL" would be
> typical.  What I'm curious about is the use of the comma operator.
> I'm not opposed to it; I'm just trying to understand why it makes a
> difference.

I guess it flags the variable as used, and prevents an overly sensitive
compiler from being loud and obnoxious... Just a guess though.

	M.
-- 
Jazz is not dead. It just smells funny...