linux-kernel - Re: [PATCH v2] drm/prime: fix extracting of the DMA addresses from a scatterlist

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Message-ID: <20200328071827.GA3648919@kroah.com>
Date:   Sat, 28 Mar 2020 08:18:27 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-samsung-soc@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Alex Deucher <alexander.deucher@....com>,
        Shane Francis <bigbeeshane@...il.com>,
        "Michael J . Ruhl" <michael.j.ruhl@...el.com>
Subject: Re: [PATCH v2] drm/prime: fix extracting of the DMA addresses from a
 scatterlist

On Fri, Mar 27, 2020 at 05:21:26PM +0100, Marek Szyprowski wrote:
> Scatterlist elements contains both pages and DMA addresses, but one
> should not assume 1:1 relation between them. The sg->length is the size
> of the physical memory chunk described by the sg->page, while
> sg_dma_len(sg) is the size of the DMA (IO virtual) chunk described by
> the sg_dma_address(sg).
> 
> The proper way of extracting both: pages and DMA addresses of the whole
> buffer described by a scatterlist it to iterate independently over the
> sg->pages/sg->length and sg_dma_address(sg)/sg_dma_len(sg) entries.
> 
> Fixes: 42e67b479eab ("drm/prime: use dma length macro when mapping sg")
> Signed-off-by: Marek Szyprowski <m.szyprowski@...sung.com>
> Reviewed-by: Alex Deucher <alexander.deucher@....com>
> ---
>  drivers/gpu/drm/drm_prime.c | 37 +++++++++++++++++++++++++------------
>  1 file changed, 25 insertions(+), 12 deletions(-)

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>