Re: [PATCH] of: Devices with pci_epf_bus_type require DMA configuration

[Christoph Hellwig]

On Mon, Oct 23, 2017 at 11:13:23AM +0530, Kishon Vijay Abraham I wrote:
> EPF devices use EPC devices which in turn use the actual platform device for
> configuring the hardware. IMO the devices in one layer shouldn't have to
> explicitly use devices in another layer other than using clearly defined API's.
> Here platform_device is the bottom later, above which is epc_device and on top
> is epf_device.
> 
> The idea is just by doing the initial setup in the framework, the epf driver be
> able to use APIs like dma_alloc_coherent using it's own *device* rather than
> the EPC's "device".

That's a little strange - normally we only call dma_map* routines on
the actual physical bus devices.