linux-kernel - Re: [PATCH 12/16] staging/comedi: mark as broken

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Message-ID: <20190614153032.GD18049@kroah.com>
Date:   Fri, 14 Jun 2019 17:30:32 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        devel@...verdev.osuosl.org, linux-s390@...r.kernel.org,
        Intel Linux Wireless <linuxwifi@...el.com>,
        linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        intel-gfx@...ts.freedesktop.org, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org,
        "moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>,
        linux-media@...r.kernel.org
Subject: Re: [PATCH 12/16] staging/comedi: mark as broken

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:
> > 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