linux-kernel - Re: [PATCH v2] dt: platform driver: Fill the resources before probe and defer if needed

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Date:	Thu, 20 Mar 2014 16:11:18 +0000
From:	Grant Likely <grant.likely@...retlab.ca>
To:	Jean-Jacques Hiblot <jjhiblot@...phandler.com>
Cc:	Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
	devicetree <devicetree@...r.kernel.org>,
	gregkh <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	robh+dt <robh+dt@...nel.org>,
	Gregory CLEMENT <gregory.clement@...e-electrons.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v2] dt: platform driver: Fill the resources before probe and defer if needed

On Mon, 17 Mar 2014 16:20:03 +0100, Jean-Jacques Hiblot <jjhiblot@...phandler.com> wrote:
> 2014-03-17 15:24 GMT+01:00 Grant Likely <grant.likely@...retlab.ca>:
> > On Mon, 17 Mar 2014 12:07:37 +0100, Jean-Jacques Hiblot <jjhiblot@...phandler.com> wrote:
> >> Hi Grant,
> >>
> >> Sorry for the delay, I was having nice vacations.
> >>
> >> 2014-03-08 8:37 GMT+01:00 Grant Likely <grant.likely@...aro.org>:
> >> > On Fri, 21 Feb 2014 14:18:40 +0100, Jean-Jacques Hiblot <jjhiblot@...phandler.com> wrote:
> >> >> The goal of this patch is to allow drivers to be probed even if at the time of
> >> >> the DT parsing some of their ressources are not available yet.
> >> >
> >> > Hi Jean-Jacques
> >> >
> >> > [...]
> >> >> +int of_platform_device_prepare(struct platform_device *dev)
> >> >> +{
> >> >> +     struct device_node *np;
> >> >> +     int i, irq_index;
> >> >> +     struct resource *res;
> >> >> +
> >> >> +     /*
> >> >> +      * This function applies only devices described in the DT.
> >> >> +      * Other platform devices have their ressources already populated.
> >> >> +      */
> >> >> +     np = dev->dev.of_node;
> >> >> +     if (!np)
> >> >> +             return 0;
> >> >
> >> > I believe we already talked about the above test. This function must
> >> > only process devices created by of_platform_populate(). Merely checking
> >> > the of_node pointer is not a sufficient test because there are other
> >> > paths in the kernel for creating platform_devices that might get a node
> >> > pointer attached to it.
> >> Yes we talked about this, but only to move it into of_platform_device_prepare().
> >> Is there an existing way to know for sure that the device has been
> >> created by of_platform_populate() ? I could not find one.
> >
> > No there isn't. That information is used at population time and then
> > discarded. We'd need to add a flag or registry to mark those devices.
> OK. As I see it, this could be done either by adding a new flag to
> struct device or by maintaining a private list of "of created" devices
> in of/platform.c.
> I favor modifying struct device as it's is by far the simplest but
> it's also more intrusive. Any advice ?

I think that by far is the easiest. It is that, or
of_platform_populate() would need to maintain a list of devices that are
to be used as a platform bus.

g.

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