Re: [PATCH 0/3] Add VGA support for Apalis iMX6

[Francesco Dolcini <francesco@dolcini.it>]

On Tue, Oct 13, 2026 at 01:11:58PM +0200, Laurent Pinchart wrote:
> On Tue, Oct 13, 2026 at 11:06:31AM +0200, Francesco Dolcini wrote:
> > On Mon, Oct 12, 2026 at 06:40:54PM +0200, Laurent Pinchart wrote:
> > > On Mon, Oct 12, 2026 at 04:25:22AM -0300, Leonardo Costa wrote:
> > > > This series adds a device tree overlay that enables the VGA output on Apalis
> > > > iMX6, which is driven from a parallel RGB interface passing through a
> > > > non-programmable video DAC.
> > > > 
> > > > The video DAC is a simple resistor network gated by an active-low
> > > > data-enable signal. For the bridge to work properly, this series also
> > > > changes the following in the dt-bindings and simple-bridge driver:
> > > > 
> > > > - dt-bindings: Add a new compatible for the bridge in the simple-bridge
> > > >   binding. This is necessary because the existing dumb-vga-dac compatible
> > > >   doesn't describe a data-enable signal polarity.
> > > > 
> > > > - simple-bridge: Add the VGA bridge match-table entry and timings
> > > >   struct, setting the DRM_BUS_FLAG_DE_LOW flag for the bridge.
> > > 
> > > Is there schematics available anywhere ? That would help reviewing the
> > > series ?
> > 
> > This circuit is on the SoM, and the SoM schematics are
> > confidential and not generally available.
> > 
> > I tried to extract as ascii art the relevant circuit, hope it helps
> 
> Thank you, it makes things clearer.
> 
> The circuit seems fairly generic. Wouldn't it be better to add an
> optional property ot the dumb-vga-dac instead of a new compatible string
> specific to Apalis ?

We discussed this internally and we were not 100% sure, so we decided to
go with this proposal that seemed easier and less controversial.

With that wrote, I let Leonardo comment on the pro/cons of the two
approaches.

Francesco