linux-kernel - Re: [PATCH 23/24] drm/bridge: require the .owner to be filled in on drm_bridge_attach

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Date:   Mon, 30 Apr 2018 17:24:38 +0200
From:   Daniel Vetter <daniel@...ll.ch>
To:     Peter Rosin <peda@...ntia.se>
Cc:     linux-kernel@...r.kernel.org,
        Martyn Welch <martyn.welch@...labora.co.uk>,
        David Airlie <airlied@...ux.ie>,
        dri-devel@...ts.freedesktop.org,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        linux-samsung-soc@...r.kernel.org,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Kukjin Kim <kgene@...nel.org>,
        Peter Senna Tschudin <peter.senna@...labora.com>,
        Martin Donnelly <martin.donnelly@...com>,
        linux-arm-msm@...r.kernel.org, Jyri Sarha <jsarha@...com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Vincent Abriou <vincent.abriou@...com>,
        linux-arm-kernel@...ts.infradead.org,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        linux-renesas-soc@...r.kernel.org,
        linux-mediatek@...ts.infradead.org, freedreno@...ts.freedesktop.org
Subject: Re: [PATCH 23/24] drm/bridge: require the .owner to be filled in on
 drm_bridge_attach

On Fri, Apr 27, 2018 at 12:31:38AM +0200, Peter Rosin wrote:
> The .owner will be handy to have around.
> 
> Signed-off-by: Peter Rosin <peda@...ntia.se>
> ---
>  drivers/gpu/drm/drm_bridge.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 9f023bd84d56..a038da696802 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -115,6 +115,9 @@ int drm_bridge_attach(struct drm_encoder *encoder, struct drm_bridge *bridge,
>  	if (!encoder || !bridge)
>  		return -EINVAL;
>  
> +	if (WARN_ON(!bridge->owner))
> +		return -EINVAL;

I think conceptually this is checked at the wrong place, and I think also misnamed
a bit. The ->owner is essentially the struct device (and its associated
driver) that provides the drm_bridge. As such it should be filled out
already at drm_bridge_add() time, and I think the check should be in
there. For driver-internal bridges it might make sense to also check this
here, not sure. Or just require all bridges get added.

Wrt the name, I think we should call this pdev or something. ->owner
usually means the module owner. I think in other subsystems ->dev is used,
but in drm we use ->dev for the drm_device pointer, so totally different
thing. pdev = physical device is the best I came up with. Better
suggestions very much welcome.
-Daniel

> +
>  	if (previous && (!previous->dev || previous->encoder != encoder))
>  		return -EINVAL;
>  
> -- 
> 2.11.0
> 
> _______________________________________________
> dri-devel mailing list
> dri-devel@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

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