Subject: Re: [PATCH 12/16] staging/comedi: mark as broken

From: Christoph Hellwig <[email-masked]>
Date: Fri, 14 Jun 2019 16:48:57 +0200

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