Hello, On Thursday 06 Oct 2016 17:09:57 Archit Taneja wrote: > On 10/06/2016 12:51 PM, Maxime Ripard wrote: > > On Mon, Oct 03, 2016 at 04:40:57PM +0530, Archit Taneja wrote: > >> On 09/30/2016 08:07 PM, Maxime Ripard wrote: > >>> Some boards have an entirely passive RGB to VGA bridge, based on either > >>> DACs or resistor ladders. > >>> > >>> Those might or might not have an i2c bus routed to the VGA connector in > >>> order to access the screen EDIDs. > >>> > >>> Add a bridge that doesn't do anything but expose the modes available on > >>> the screen, either based on the EDIDs if available, or based on the XGA > >>> standards. > >>> > >>> Acked-by: Rob Herring <robh@xxxxxxxxxx> > >>> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> > >>> --- > >>> .../bindings/display/bridge/rgb-to-vga-bridge.txt | 48 +++++ > >>> drivers/gpu/drm/bridge/Kconfig | 7 + > >>> drivers/gpu/drm/bridge/Makefile | 1 + > >>> drivers/gpu/drm/bridge/rgb-to-vga.c | 229 +++++++++++++++ > >>> 4 files changed, 285 insertions(+) > >>> create mode 100644 > >>> Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.txt > >>> create mode 100644 drivers/gpu/drm/bridge/rgb-to-vga.c > >>> > >>> diff --git > >>> a/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.tx > >>> t > >>> b/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.tx > >>> t new file mode 100644 > >>> index 000000000000..a8375bc1f9cb > >>> --- /dev/null > >>> +++ > >>> b/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge.tx > >>> t @@ -0,0 +1,48 @@ > >>> +Dumb RGB to VGA bridge > >>> +---------------------- > >>> + > >>> +This binding is aimed for dumb RGB to VGA bridges that do not require > >>> +any configuration. > >>> + > >>> +Required properties: > >>> + > >>> +- compatible: Must be "rgb-to-vga-bridge" > >> > >> I'd talked to Laurent on IRC if he's okay with this. And I guess you to > >> had discussed it during XDC too. He's suggested that it'd be better to > >> have the compatible string as "simple-vga-dac". > > > > I just wished this bikeshedding had taken place publicly and be > > actually part of that discussion, but yeah, ok. > > Sorry about that. I'd pinged him for an Ack, the discussion went > more than that :) > > >> Some of the reasons behind having this: > >> > >> - We don't need to specify "rgb" in the compatible string since most > >> simple VGA DACs can only work with an RGB input. > > > > Ok. > > > >> - Also, with "dac" specified in the string, we don't need to > >> specifically mention "bridge" in the string. Also, bridge is a drm > >> specific term. > >> > >> - "simple" is considered because it's an unconfigurable bridge, and it > >> might be misleading for other VGA DACs to not use "vga-dac". > > > > All those "simple" bindings are just the biggest lie we ever > > told. It's simple when you introduce it, and then grows into something > > much more complicated than a non-simple implementation. > > "simple" here is supposed to mean that it's an unconfigurable RGB to > VGA DAC. This isn't supposed to follow the simple-panel model, where > you add the "simple-panel" string in the compatible node, along with > you chip specific compatible string. I agree with Maxime, I don't like the word "simple". My preference would be "vga-dac" for a lack of a better qualifier than "simple" to describe the fact that the device requires no configuration. My only concern with "vga-dac" is that we would restrict usage of that compatible string for a subset of VGA DACs, with more complex devices not being compatible with "vga-dac" even though they are VGA DACs. That's a problem I can live with though. > In other words, this driver shouldn't be touched again in the future :) > If someone wants to write a RGB to VGA driver which is even > slightly configurable, they'll need to write a new bridge driver. I'm sure that won't be true. I can certainly foresee the addition of regulators support for instance. It's unfortunately never black and white. > >> What do you think about this? If you think it's good, would it be > >> possible for you to change this? I guess it's okay for the rest of > >> the patch to stay the same. > > > > I'll update and respin the serie. -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
