On Wed, Oct 28, 2020 at 05:55:23PM +1100, Alexey Kardashevskiy wrote:

It is passing an address of the end of the mapped area so passing a page 
struct means passing page and offset which is an extra parameter and we do 
not want to do anything with the page in those hooks anyway so I'd keep it 
as is.

quoted

and
    maybe even hide the dma_map_direct inside it.

Call dma_map_direct() from arch_dma_map_page_direct() if 
arch_dma_map_page_direct() is defined? Seems suboptimal as it is going to 
be bypass=true in most cases and we save one call by avoiding calling 
arch_dma_map_page_direct(). Unless I missed something?

C does not even evaluate the right hand side of a || expression if the
left hand evaluates to true.