linux-kernel - Re: [PATCH v2 1/4] of/pci: Add of_pci_check_probe

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Date:	Wed, 2 Sep 2015 17:23:25 -0500
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Rob Herring <robherring2@...il.com>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Will Deacon <will.deacon@....com>,
	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Alexander Graf <agraf@...e.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] of/pci: Add of_pci_check_probe_only to parse
 "linux,pci-probe-only"

On Fri, Aug 14, 2015 at 04:08:10PM -0500, Rob Herring wrote:
> On Fri, Aug 14, 2015 at 11:19 AM, Marc Zyngier <marc.zyngier@....com> wrote:
> > Both pci-host-generic and Pseries parse the "linux,pci-probe-only"
> > to engage the PCI_PROBE_ONLY mode, and both have a subtle bug that
> > can be triggered if the property has no parameter.
> 
> Humm, I bet we could break a lot of machines if we fixed the core code
> to properly make pp->value NULL when there is no value.
> 
> > Provide a generic implementation that can be used by both.
> >
> > Signed-off-by: Marc Zyngier <marc.zyngier@....com>
> > ---
> >  drivers/of/of_pci.c    | 30 ++++++++++++++++++++++++++++++
> >  include/linux/of_pci.h |  3 +++
> >  2 files changed, 33 insertions(+)
> >
> > diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> > index 5751dc5..a4e29ff 100644
> > --- a/drivers/of/of_pci.c
> > +++ b/drivers/of/of_pci.c
> > @@ -118,6 +118,36 @@ int of_get_pci_domain_nr(struct device_node *node)
> >  EXPORT_SYMBOL_GPL(of_get_pci_domain_nr);
> >
> >  /**
> > + * of_pci_check_probe_only - Setup probe only mode if linux,pci-probe-only
> > + *                           is present and valid
> > + *
> > + * @node: device tree node that may contain the property (usually "chosen")
> > + *
> > + */
> > +void of_pci_check_probe_only(struct device_node *node)
> > +{
> > +       const int *prop;
> > +       int len;
> > +
> > +       if (!node)
> > +               return;
> > +
> > +       prop = of_get_property(node, "linux,pci-probe-only", &len);
> 
> It is preferred to use of_property_read_u32 to avoid just these types
> of problems.

I don't know enough OF to really understand this, but I infer that
this is a suggestion for improving the patch.  Should I be waiting for
a v3 series?

Bjorn
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