linux-kernel - Re: [PATCH 4/6] drm/bridge: Add Analogix anx6345 support

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Message-ID: <20190523124508.GC15685@lst.de>
Date:   Thu, 23 May 2019 14:45:08 +0200
From:   Torsten Duwe <duwe@....de>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        Chen-Yu Tsai <wens@...e.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Icenowy Zheng <icenowy@...c.io>,
        Sean Paul <seanpaul@...omium.org>,
        Vasily Khoruzhick <anarsoul@...il.com>,
        Harald Geyer <harald@...ib.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6] drm/bridge: Add Analogix anx6345 support

On Thu, May 23, 2019 at 10:50:41AM +0300, Laurent Pinchart wrote:
> Hi Torsten,
> 
> Thank you for the patch.

Thank you for the thorough review!

> On Thu, May 23, 2019 at 08:53:56AM +0200, Torsten Duwe wrote:
> > +{
> > +	struct anx6345 *anx6345 = connector_to_anx6345(connector);
> > +	int err, num_modes = 0;
> > +	bool power_off = false;
> > +
> > +	mutex_lock(&anx6345->lock);
> > +
> > +	if (!anx6345->edid) {
> 
> Could the chip be used with a hot-pluggable display, or is it guaranteed
> that EDID will never change ?

The chip itself is capable of (e)DP hot-plugging, so the signals suggest.
See the previous discussions about what to expect on the output side.
Currently, the driver does not handle hot-plugging.

> > +
> > +	err = drm_of_find_panel_or_bridge(client->dev.of_node, 1, 0,
> > +					  &anx6345->panel, NULL);
> > +	if (err == -EPROBE_DEFER)
> > +		return err;
> > +
> > +	if (err)
> > +		DRM_DEBUG("No panel found\n");
> 
> Shouldn't this be fatal ?

No, basically same as above. On the output side, there can be a panel,
another bridge, or some eDP plug. If the DT didn't explicitly specify
a panel or a bridge, we can still generate video output as soon as
there is valid EDID data.

Your other points went straight onto my TODO list.

	Torsten