On Sun, Apr 15, 2018 at 11:24:11AM -0400, Alan Stern wrote: > On Sun, 15 Apr 2018, Christoph Hellwig wrote: > > > USB host controllers now must handle highmem, so we can get rid of bounce > > buffering highmem pages in the block layer. > > Sorry, I don't quite understand what you are saying. Do you mean that > all USB host controllers now magically _do_ handle highmem? Or do you > mean that if they _don't_ handle highmem, we will not support them any > more?
USB controller themselves never cared about highmem, drivers did. For PIO based controllers they'd have to kmap any address no in the kernel drirect mapping. Nothing in drivers/usb/host or the other diretories related to host drivers calls page_address (only used in a single gadget) or sg_virt (only used in a few upper level drivers), which makes me assume semi-confidently that no USB host driver is not highmem aware these days. Greg, does this match your observation as the USB maintainer?
