On Thursday, September 1, 2016 5:14:28 PM CEST Leo Li wrote: > > Hi Felipe and Arnd, > > It has been a while since the last response to this discussion, but we > haven't reached an agreement yet! Can we get to a conclusion on if it > is valid to create child platform device for abstraction purpose? If > yes, can this child device do DMA by itself? I'd say it's no problem for a driver to create child devices in order to represent different aspects of a device, but you should not rely on those devices working when used with the dma-mapping interfaces. This used to be simpler back when we could configure the kernel for only one SoC platform at a time, and the platforms could provide their own overrides for the dma-mapping interfaces. These days, we rely on firmware or bootloader to describe various aspects of how DMA is done, so you can't assume that passing a device without an of_node pointer or ACPI data into those functions will do the right thing. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
