Re: New LCD connector type?

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: dri-devel@lists.freedesktop.org,
	Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Subject: Re: New LCD connector type?
Date: Mon, 9 May 2016 15:07:21 +0300	[thread overview]
Message-ID: <20160509120721.GJ4329@intel.com> (raw)
In-Reply-To: <2460709.tEGL1JKEHm@avalon>

On Mon, May 09, 2016 at 02:43:02PM +0300, Laurent Pinchart wrote:
> Hi Ville,
> 
> On Saturday 07 May 2016 21:11:23 Ville Syrjälä wrote:
> > On Fri, May 06, 2016 at 10:01:29PM +0300, Sergei Shtylyov wrote:
> > > (Resending as I couldn't find this message from January in the list
> > > archives.)
> > > 
> > > Hello.
> > > 
> > > We have a board which has Newhaven Display LCD [1] connected via a
> > > what seems to be a custom 40-signal LCD connector. That connector includes
> > > (6-bit per component) RGB signals, DISP, H/VSYNC, and the pixel clock
> > > signals; in addition, there are I2C and IRQ signals.
> > > 
> > > Now we need to add support for this kind of connector to the R-Car DU
> > > driver in order to get the LCD panel resolution from the device tree (see
> > > drivers/gpu/drm/rcar-du/rcar_du_*con.c for the examples) and so we'd
> > > probably need a new DRM_MODE_CONNECTOR_* constant in
> > > include/uapi/drm/drm_mode.h in order to do that... Laurent advised me to
> > > ask for the opinions on the dri-devel mailing list first, which I'm
> > > doing. :-)
> > 
> > I'd just make it LVDS.
> 
> Even if the connector doesn't carry LVDS signals ?

No one should really have to care about such details for any purely
internal connector. IMO the fact that the thing we have is called
LVDS could be considered a historical accident.

We do have eDP and DSI types too though, which I might not have even
bothered to add myself. These days eDP does make some sense as we expose
the AUX ch via /dev so eDP vs. other internal connectors does have some
user visible difference at least. And I guess you could justify DSI by
the fact that it's a widely used standard.

If people feel anal about this, I guess you could always add some kind
of generic internal connector type to account for everything that isn't
LVDS/eDP/DSI. But a new type means that you'll have to modify userspace
to deal with the new connector type, at least if you want to name the
connector based on its type (which is the norm).

-- 
Ville Syrjälä
Intel OTC
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