linux-kernel - Re: [PATCH v8 2/9] pci: Export find_pci_host

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Message-ID: <20140703095302.GY2173@e106497-lin.cambridge.arm.com>
Date:	Thu, 3 Jul 2014 10:53:02 +0100
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Tanmay Inamdar <tinamdar@....com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	linux-pci <linux-pci@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Device Tree ML <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	patches <patches@....com>
Subject: Re: [PATCH v8 2/9] pci: Export find_pci_host_bridge() function.

On Wed, Jul 02, 2014 at 09:43:41PM +0100, Tanmay Inamdar wrote:
> On Wed, Jul 2, 2014 at 12:12 PM, Arnd Bergmann <arnd@...db.de> wrote:
> > On Wednesday 02 July 2014 11:06:38 Tanmay Inamdar wrote:
> >> On Tue, Jul 1, 2014 at 11:43 AM, Liviu Dudau <Liviu.Dudau@....com> wrote:
> >> > This is a useful function and we should make it visible outside the
> >> > generic PCI code. Export it as a GPL symbol.
> >> >
> >> > Signed-off-by: Liviu Dudau <Liviu.Dudau@....com>
> >> > Tested-by: Tanmay Inamdar <tinamdar@....com>
> >> > ---
> >> >  drivers/pci/host-bridge.c | 3 ++-
> >> >  1 file changed, 2 insertions(+), 1 deletion(-)
> >> >
> >> > diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c
> >> > index 0e5f3c9..36c669e 100644
> >> > --- a/drivers/pci/host-bridge.c
> >> > +++ b/drivers/pci/host-bridge.c
> >> > @@ -16,12 +16,13 @@ static struct pci_bus *find_pci_root_bus(struct pci_bus *bus)
> >> >         return bus;
> >> >  }
> >> >
> >> > -static struct pci_host_bridge *find_pci_host_bridge(struct pci_bus *bus)
> >> > +struct pci_host_bridge *find_pci_host_bridge(struct pci_bus *bus)
> >> >  {
> >> >         struct pci_bus *root_bus = find_pci_root_bus(bus);
> >> >
> >> >         return to_pci_host_bridge(root_bus->bridge);
> >> >  }
> >> > +EXPORT_SYMBOL_GPL(find_pci_host_bridge);
> >>
> >> Is there any specific reason behind making this symbol GPL? I think
> >> the other functions in this file are just EXPORT_SYMBOL. Ultimately
> >> companies which have non gpl Linux modules (nvidia) will face issue
> >> using this API.
> >>
> >> The same applies to 'of_create_pci_host_bridge'.
> >
> > I think EXPORT_SYMBOL_GPL() is better here. The new symbols are unlikely
> > to be used by a peripheral device driver, and PCI host controllers are
> > already restricted by EXPORT_SYMBOL_GPL.
> >
> 
> You are right as long as the functions are not used directly. But what
> if GPL functions are called indirectly.  For example, 'pci_domain_nr'
> implementation in Liviu's V7 series calls 'find_pci_host_bridge'.

I will not be drawn into the discussion of EXPORT_SYMBOL vs EXPORT_SYMBOL_GPL()
other than to say that I don't understand what is so secret in implementing
a standard. I do not want to support host bridge drivers that are not open
source.

Best regards,
Liviu

> 
> > nvidia will certainly not do a PCI host controller driver that is not
> > upstream or not GPL-compatible.
> >
> >         Arnd
> 

-- 
====================
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| fix the world,  |
| but they're not |
| giving me the   |
 \ source code!  /
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