On 12/12/2013 07:14 PM, Greg KH wrote: > On Thu, Dec 12, 2013 at 11:39:20AM +0000, Grant Likely wrote: >> On Thu, 12 Dec 2013 09:57:05 +0200, Hiroshi Doyu <hdoyu@xxxxxxxxxx> wrote: >>> IOMMU devices on the bus need to be poplulated first, then iommu >>> master devices are done later. >>> >>> With CONFIG_OF_IOMMU, "iommus=" DT binding would be used to identify >>> whether a device can be an iommu msater or not. If a device can, we'll >>> defer to populate that device till an iommu device is populated. Then, >>> those deferred iommu master devices are populated and configured with >>> help of the already populated iommu device. >>> This is related to the following discussion: >>> [RFC PATCH] Documentation: devicetree: add description for generic bus properties >>> http://lists.infradead.org/pipermail/linux-arm-kernel/2013-November/215042.html >>> diff --git a/drivers/base/dd.c b/drivers/base/dd.c >>> @@ -273,6 +274,10 @@ static int really_probe(struct device *dev, struct device_driver *drv) >>> >>> dev->driver = drv; >>> >>> + ret = of_iommu_attach(dev); >>> + if (ret) >>> + goto probe_failed; >>> + >> >> As discussed before, I really don't think hooking in to dd.c is the >> right thing to do here, and certainly not as a device tree specific >> function. ACPI or PCI described devices may have the same constraints >> and those won't have DT descriptions. > > I agree, this shouldn't be in the driver core. I don't think I agree. It'd greatly simplify driver probe() routines if the driver core could acquire/set up as many resources as it could on behalf of drivers. It'd be nice if it pre-mapped any registers, acquired clocks, regulators, ... That way, we wouldn't need to write all that code in each individual driver's probe() routine. Now, in many cases this is rather difficult since there's currently no way for the driver core to know which resources a driver needs, but when the driver core can/does know this, shouldn't it simplify the life of drivers? Longer-term, perhaps drivers can provide the driver core with some specification of the resources it needs (such as a list of clock, regulator, ... names), to fill in the missing information. -- 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
