linux-kernel - Re: [PATCH v3 16/17] platform/chrome: cros_ec

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Message-ID: <ZsxRxpyqsslvQFO2@smile.fi.intel.com>
Date: Mon, 26 Aug 2024 12:58:30 +0300
From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To: Stephen Boyd <swboyd@...omium.org>
Cc: Tzung-Bi Shih <tzungbi@...nel.org>, chrome-platform@...ts.linux.dev,
	linux-kernel@...r.kernel.org, patches@...ts.linux.dev,
	devicetree@...r.kernel.org,
	Douglas Anderson <dianders@...omium.org>,
	Pin-yen Lin <treapking@...omium.org>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Benson Leung <bleung@...omium.org>,
	Conor Dooley <conor+dt@...nel.org>, Daniel Vetter <daniel@...ll.ch>,
	David Airlie <airlied@...il.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	dri-devel@...ts.freedesktop.org,
	Guenter Roeck <groeck@...omium.org>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Jonas Karlman <jonas@...boo.se>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Lee Jones <lee@...nel.org>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Prashant Malani <pmalani@...omium.org>,
	Robert Foss <rfoss@...nel.org>, Rob Herring <robh+dt@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Alexandre Belloni <alexandre.belloni@...tlin.com>,
	Daniel Scally <djrscally@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Ivan Orlov <ivan.orlov0322@...il.com>, linux-acpi@...r.kernel.org,
	linux-usb@...r.kernel.org,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	"Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Vinod Koul <vkoul@...nel.org>
Subject: Re: [PATCH v3 16/17] platform/chrome: cros_ec_typec: Support DP
 muxing

On Fri, Aug 23, 2024 at 01:44:41PM -0700, Stephen Boyd wrote:
> Quoting Tzung-Bi Shih (2024-08-22 07:37:05)
> > On Mon, Aug 19, 2024 at 03:38:30PM -0700, Stephen Boyd wrote:

...

> > > +     /*
> > > +      * Assume the first port to have HPD asserted is the one muxed to DP
> > > +      * (i.e. active_port). When there's only one port this delays setting
> > > +      * the active_port until HPD is asserted, but before that the
> > > +      * drm_connector looks disconnected so active_port doesn't need to be
> > > +      * set.
> > > +      */
> > > +     if (dp_bridge && hpd_asserted && !dp_bridge->active_port)
> > > +             dp_bridge->active_port = port;
> > > +
> > > +     is_active_port = !dp_bridge || dp_bridge->active_port == port;
> >
> > Why `!dp_bridge`?  When will `dp_bridge` be NULL?
> 
> I'll add a comment.
> 
> 'dp_bridge' is NULL when this driver is running on non-DT platforms,
> i.e. ACPI, or there isn't a graph/ports node for this device. The latter
> could happen if there's some AP controlled piece of hardware that is a
> typec switch, connected directly to a usb-c-connector. This is the case
> on Kukui where we send the DP lanes directly to the usb-c-connector.

Thanks!

-- 
With Best Regards,
Andy Shevchenko