linux-kernel - Re: [PATCH v3 2/2] dt: platform driver: Fill the resources before probe and defer if needed

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Date:	Fri, 18 Apr 2014 16:24:07 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Rob Herring <robherring2@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <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 v3 2/2] dt: platform driver: Fill the resources before
 probe and defer if needed

* Russell King - ARM Linux <linux@....linux.org.uk> [140418 16:04]:
> On Fri, Apr 18, 2014 at 02:58:48PM -0700, Tony Lindgren wrote:
> > Oh come on, let's stop pretending it's not broken. And it's way worse with
> > device tree as there's nothing making sure the resources for a driver
> > are set up before the driver probes. And we've been unable to fix just
> > this issue alone for about six months now. It's also broken beyond that.
> > It's called of_platform_bus yet it won't even pass the platform_data
> > as auxdata to the devices on a sub-bus instantatiated like I2C.
> 
> Isn't there a much simpler solution to the platform device IRQ problem?
> 
> Rather than trying to fix it at the point where the resources are
> created, why not just *not* have DT create the IRQ resources in the
> first place, and instead have platform_get_irq() (which is the function
> which should be used to get an IRQ) be the actor to do whatever is
> necessary to return the IRQ(s) ?

Yeah why not. I don't see why we would need to do all this of_* special
trickery for much anything beyond parsing the binding.
 
> Yes, I know we have some drivers which use platform_get_resources() with
> IORESOURCE_IRQ, but they should really use the right accessor.  And those
> who just dereference the resource array directly... get what's coming
> (though of course they have to be fixed.)

$ git grep IORESOURCE_IRQ drivers/ | grep platform_get_resource | wc -l
179

But might be scriptable to some extent..
 
> It has the benefit that you're in a path where you /can/ return
> -EPROBE_DEFER too and not have to mess around with notifiers or other
> silly stuff like that.

And then maybe we can make of_platform_probe() or some bus function
do the most of the -EPROBE_DEFER ping pong before the driver even
probes?

Regards,

Tony
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