linux-kernel - Re: [PATCH v2 2/6] drm: lcdif: Drop unnecessary NULL pointer check on lcdif->bridge

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Message-ID: <4ec549dcec8686b9d1eed619965fde0b17736f17.camel@nxp.com>
Date:   Thu, 26 Jan 2023 10:10:38 +0800
From:   Liu Ying <victor.liu@....com>
To:     Marek Vasut <marex@...x.de>, dri-devel@...ts.freedesktop.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Cc:     stefan@...er.ch, airlied@...il.com, daniel@...ll.ch,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
        festevam@...il.com, linux-imx@....com,
        krzysztof.kozlowski@...aro.org, LW@...O-electronics.de,
        alexander.stein@...tq-group.com
Subject: Re: [PATCH v2 2/6] drm: lcdif: Drop unnecessary NULL pointer check
 on lcdif->bridge

On Wed, 2023-01-25 at 14:56 +0100, Marek Vasut wrote:
> On 1/25/23 07:40, Liu Ying wrote:
> > A valid bridge is already found in lcdif_attach_bridge() and set
> > to lcdif->bridge, so lcdif->bridge cannot be a NULL pointer. Drop
> > the unnecessary NULL pointer check in KMS stage.
> 
> Is it possible that a panel (instead of a bridge) be attached to
> LCDIFv3 
> e.g. in case of iMXRT ?

According to IMXRT1160 and IMXRT1170 reference manuals, it looks like
LCDIFv2(similar to LCDIFv3, but not the same) may connect to a parallel
display panel through a mux(either eLCDIF or LCDIFv2).  That mux could
be a bridge.  But, it doesn't matter, because devm_drm_of_get_bridge()
may create a panel bridge if a panel is connected directly(See
kerneldoc of devm_drm_of_get_bridge()).

Regards,
Liu Ying

> 
> > Signed-off-by: Liu Ying <victor.liu@....com>
> > ---
> > v1->v2:
> > * Split from patch 2/2 in v1. (Marek, Alexander)
> 
> Much appreciated, thanks.
> 
> [...]