Stephen Warren <swarren@xxxxxxxxxxxxx> wrote @ Thu, 31 Oct 2013 17:37:40 +0100:
> On 10/31/2013 02:14 AM, Hiroshi Doyu wrote:
> > Thierry Reding <thierry.reding@xxxxxxxxx> wrote @ Wed, 30 Oct 2013 23:41:09 +0100:
> >
> >> My earlier proposal for deferred interrupt reference resolution actually
> >> tries to solve that problem within the core. Essentially what it does is
> >> add a new function that gets called right before the driver's .probe()
> >> function, so that it can parse standard resources and services from DT,
> >> such as the interrupts property. This could theoretically be done for
> >> other resources such as reg as well, but it really only matters where
> >> the resource can be dynamic (as is the case for interrupts).
> >>
> >> In this case I would envision a standard OF function to associate a
> >> device with its IOMMU. Perhaps something like:
> >>
> >> int of_iommu_attach(struct device *dev);
> >>
> >> That could be called by the core independent of the specific device and
> >> IOMMU. IOMMU-specifics can probably be handled using .of_xlate(), quite
> >> in a similar way to GPIO or regulators.
> >>
> >> That way drivers can remain agnostic of the IOMMU while still being able
> >> to take advantage of deferred probing.
> >
> > This could be simpler than making "bus_notifier" return "-EPROBE_DEFER".
> >
> > The disadvantage of this is that we may need to provide the similar
> > of_<"subsystem">_attach() per subsytem if needed.
>
> Well, "per subsystem" here means per subsystem that is providing
> resources, not per subsystem that is consuming resources. How many
> subsystems are you expecting to provide resources like this? At present,
> I believe IOMMU is the only subsystem missing some kind of API for
> clients to acquire the relevant resource. I don't think there's any
> scalability problem here.
Honestly I have no idea for other subsystem which needs
of_<"subsystem">_attach(). But IIRC, it's almost similar one to the
following "pinctrl_bind_pins()"? Or something other way?
drivers/base/dd.c:
static int really_probe(struct device *dev, struct device_driver *drv)
{
int ret = 0;
atomic_inc(&probe_count);
pr_debug("bus: '%s': %s: probing driver %s with device %s\n",
drv->bus->name, __func__, drv->name, dev_name(dev));
WARN_ON(!list_empty(&dev->devres_head));
dev->driver = drv;
/* If using pinctrl, bind pins now before probing */
ret = pinctrl_bind_pins(dev);
^^^^^^^^^^^^^^^^^^^^^^^
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