linux-kernel - Re: [PATCH] drm/bridge: dw-hdmi: Refuse DDC/CI transfers on the internal I2C controller

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Date:   Fri, 19 Jul 2019 09:45:45 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Adam Jackson <ajax@...hat.com>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jose Abreu <Jose.Abreu@...opsys.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Douglas Anderson <dianders@...omium.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: dw-hdmi: Refuse DDC/CI transfers on the
 internal I2C controller

On Fri, Jul 19, 2019 at 12:23:26PM -0400, Adam Jackson wrote:
> On Thu, 2019-07-18 at 14:41 -0700, Matthias Kaehlcke wrote:
> 
> > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > index 045b1b13fd0e..e49402ebd56f 100644
> > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > @@ -35,6 +35,7 @@
> >  
> >  #include <media/cec-notifier.h>
> >  
> > +#define DDC_I2C_ADDR		0x37
> 
> This confused the heck out of me to read, DDC by definition happens
> over I2C and this one address is just for a specific subset of DDC.
> Perhaps this would be clearer if it was named DDC_CI_ADDR.

I was also a bit confused about the terminology, some places call 0x37
the DDC address and 0x50 the EDID address.

DDC_CI_ADDR sounds good to me, thanks for the suggestion!

I'll wait a day or two before respinning, for if there are more comments.