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

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Message-ID: <20190614140239.GA7234@kroah.com>
Date:   Fri, 14 Jun 2019 16:02:39 +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 03:47:22PM +0200, Christoph Hellwig wrote:
> comedi_buf.c abuse the DMA API in gravely broken ways, as it assumes it
> can call virt_to_page on the result, and the just remap it as uncached
> using vmap.  Disable the driver until this API abuse has been fixed.
> 
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
>  drivers/staging/comedi/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/staging/comedi/Kconfig b/drivers/staging/comedi/Kconfig
> index 049b659fa6ad..e7c021d76cfa 100644
> --- a/drivers/staging/comedi/Kconfig
> +++ b/drivers/staging/comedi/Kconfig
> @@ -1,6 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  config COMEDI
>  	tristate "Data acquisition support (comedi)"
> +	depends on BROKEN

Um, that's a huge sledgehammer.

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.

thanks,

greg k-h