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); ^^^^^^^^^^^^^^^^^^^^^^^ -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html