Thierry Reding <thierry.reding@xxxxxxxxx> wrote @ Fri, 1 Nov 2013 10:53:50 +0100: > * PGP Signed by an unknown key > > On Thu, Oct 31, 2013 at 10:37:40AM -0600, Stephen Warren wrote: > > 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. > > Furthermore if the subsystem wants to provide resources then it needs > such a function anyway, so there really isn't any overhead here. Ok, the scalability won't be an issue since the number of subsystems to provide resources/services is usually limited, anyway. -- 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
