02.10.2020 04:07, Nicolin Chen пишет: > On Thu, Oct 01, 2020 at 11:33:38PM +0300, Dmitry Osipenko wrote: >>>>> If we can't come to an agreement on globalizing mc pointer, would >>>>> it be possible to pass tegra_mc_driver through tegra_smmu_probe() >>>>> so we can continue to use driver_find_device_by_fwnode() as v1? >>>>> >>>>> v1: https://lkml.org/lkml/2020/9/26/68 >>>> >>>> tegra_smmu_probe() already takes a struct tegra_mc *. Did you mean >>>> tegra_smmu_probe_device()? I don't think we can do that because it isn't >>> >>> I was saying to have a global parent_driver pointer: similar to >>> my v1, yet rather than "extern" the tegra_mc_driver, we pass it >>> through egra_smmu_probe() and store it in a static global value >>> so as to call tegra_smmu_get_by_fwnode() in ->probe_device(). >>> >>> Though I agree that creating a global device pointer (mc) might >>> be controversial, yet having a global parent_driver pointer may >>> not be against the rule, considering that it is common in iommu >>> drivers to call driver_find_device_by_fwnode in probe_device(). >> >> You don't need the global pointer if you have SMMU OF node. >> >> You could also get driver pointer from mc->dev->driver. >> >> But I don't think you need to do this at all. The probe_device() could >> be invoked only for the tegra_smmu_ops and then seems you could use >> dev_iommu_priv_set() in tegra_smmu_of_xlate(), like sun50i-iommu driver >> does. > > Getting iommu device pointer using driver_find_device_by_fwnode() > is a common practice in ->probe_device() of other iommu drivers. Please give me a full list of the IOMMU drivers which use this method. > But this requires a device_driver pointer that tegra-smmu doesn't > have. So passing tegra_mc_driver through tegra_smmu_probe() will > address it. > If you're borrowing code and ideas from other drivers, then at least please borrow them from a modern good-looking drivers. And I already pointed out that following cargo cult is not always a good idea. ARM-SMMU isn't a modern driver and it has legacy code. You shouldn't copy it blindly. The sun50i-iommu driver was added half year ago, you may use it as a reference. Always consult the IOMMU core code. If you're too unsure about something, then maybe better to start a new thread and ask Joerg about the best modern practices that IOMMU drivers should use.
