Thierry Reding <thierry.reding@xxxxxxxxx> wrote @ Fri, 25 Oct 2013 09:56:55 +0200: > > > This patch is a part of HACK to control device instanciation order. We > > > have an IOMMU device(platform) which needs to be instanciated earlier > > > than other (platform)devices so that IOMMU driver would configure them > > > as IOMMU'able device. > > > > Ideally the drivers depending on the IOMMU would return -EPROBE_DEFER if > > the IOMMU driver isn't set up so that you don't need to play games with > > probe order. Creating certain platform devices early is a really ugly > > and fragile solution. > > > > Besides, probe order of device drivers is far more about link order of > > the kernel than it is about when of_platform_device_create() is called. > > Fiddling with the initcall level on the IOMMU driver (while not > > recommended) may very well have the effect you desire. > > This is actually "the other problem that I'm aware of that could benefit > from [interrupt resolution at probe time]". My idea was that once we had > a way within the driver core to resolve interrupt references at probe > time it could be used for potentially many other resources as well. Some > of the resources like GPIOs and regulators are obviously not something > that the core can or should be requesting, but mostly resources that you > don't actually need to control after probing (such as interrupts) would > be a good fit because otherwise people would write the same boilerplate > over and over again. > > IOMMUs seem to me to be in that same category. As far as I can tell, an > IOMMU driver registers the IOMMU for a given bus, upon which every > device can simply be used (mostly transparently) with that IOMMU. While > I haven't figured out how exactly, I'm pretty sure we can take advantage > of the resolution of resources at probe time within the core to both > keep drivers from having to do anything in particular and at the same > time have code to determine if the IOMMU driver hasn't been probed yet > and return -EPROBE_DEFER appropriately. Can you explain the above a bit more? Originally I thought that what Grant suggested would work ok with this patch. -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
