linux-kernel - Re: [PATCH V8 5/9] pci, acpi: add acpi hook to assign domain number.

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Message-ID: <20160610151458.GA23638@red-moon>
Date:	Fri, 10 Jun 2016 16:14:58 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Bjorn Helgaas <helgaas@...nel.org>
Cc:	Tomasz Nowicki <tn@...ihalf.com>, arnd@...db.de,
	will.deacon@....com, catalin.marinas@....com, rafael@...nel.org,
	hanjun.guo@...aro.org, okaya@...eaurora.org, jchandra@...adcom.com,
	robert.richter@...iumnetworks.com, mw@...ihalf.com,
	Liviu.Dudau@....com, ddaney@...iumnetworks.com,
	wangyijing@...wei.com, Suravee.Suthikulpanit@....com,
	msalter@...hat.com, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linaro-acpi@...ts.linaro.org,
	jcm@...hat.com, andrea.gallo@...aro.org, dhdang@....com,
	jeremy.linton@....com, liudongdong3@...wei.com, cov@...eaurora.org
Subject: Re: [PATCH V8 5/9] pci, acpi: add acpi hook to assign domain number.

Hi Bjorn, Tomasz,

On Tue, Jun 07, 2016 at 07:15:59PM -0500, Bjorn Helgaas wrote:

[...]

> > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> > index eb431b5..2b52178 100644
> > --- a/drivers/pci/pci.c
> > +++ b/drivers/pci/pci.c
> > @@ -7,6 +7,7 @@
> >   *	Copyright 1997 -- 2000 Martin Mares <mj@....cz>
> >   */
> >  
> > +#include <linux/acpi.h>
> >  #include <linux/kernel.h>
> >  #include <linux/delay.h>
> >  #include <linux/init.h>
> > @@ -4941,7 +4942,7 @@ int pci_get_new_domain_nr(void)
> >  }
> >  
> >  #ifdef CONFIG_PCI_DOMAINS_GENERIC
> > -void pci_bus_assign_domain_nr(struct pci_bus *bus, struct device *parent)
> > +static int of_pci_bus_domain_nr(struct device *parent)
> 
> Can we do a little cleanup before this patch?  
> 
>   - pci_bus_assign_domain_nr() is only used inside drivers/pci, so
>     maybe we move the prototype to drivers/pci/pci.h?
> 
>   - I don't really like the style of calling a function that
>     internally assigns bus->domain_nr.  Could we do something like
>     this instead?
> 
>     int pci_bus_domain_nr(...)
>     {
>       ...
>       return domain;
>     }
> 
>     ... pci_create_root_bus(...)
>     {
>       ...
>       b->domain_nr = pci_bus_domain_nr(...);

We noticed while preparing v9, that this would force us to
write an empty pci_bus_domain_nr() prototype for
!PCI_DOMAINS_GENERIC (ie every arch but ARM/ARM64) that should
return 0 to keep current behaviour unchanged.

That's why pci_bus_assign_domain_nr() was there, so that it
was compiled out on !PCI_DOMAINS_GENERIC.

I really would like v9 to be final so let's fix it before posting it
shortly please.

For the above we have three options:

1) Leave code as-is in v8

2) in pci_create_root_bus():
#ifdef CONFIG_PCI_DOMAINS_GENERIC
       b->domain_nr = pci_bus_domain_nr(...);
#endif

+ other changes requested above

3) in pci_create_root_bus()

b->domain_nr = pci_bus_domain_nr(...);

unguarded and a stub:

#ifndef CONFIG_PCI_DOMAINS_GENERIC
static inline int pci_bus_domain_nr() { return 0; }
#endif

+ other changes requested above

I think it is a matter of details and frankly I am not sure (2) or (3)
make things much cleaner than they are (given that as you know with
Arnd's changes we will rewrite this code anyway), so please let's
choose an option so that we can post v9 and hopefully this series is
ready to go.

Thanks !
Lorenzo