On Fri, Jun 14, 2019 at 04:48:57PM +0200, Christoph Hellwig wrote:

On Fri, Jun 14, 2019 at 04:02:39PM +0200, Greg KH wrote:

quoted

Perhaps a hint as to how we can fix this up?  This is the first time
I've heard of the comedi code not handling dma properly.

It can be fixed by:

 a) never calling virt_to_page (or vmalloc_to_page for that matter)
    on dma allocation
 b) never remapping dma allocation with conflicting cache modes
    (no remapping should be doable after a) anyway).

Ok, fair enough, have any pointers of drivers/core code that does this
correctly?  I can put it on my todo list, but might take a week or so...

Ian, want to look into doing this sooner?

thanks,

greg k-h