On 10/07/2016 02:44 PM, Maxime Ripard wrote: > On Fri, Oct 07, 2016 at 10:27:31AM +0530, Archit Taneja wrote: >> >> >> On 10/07/2016 02:34 AM, Laurent Pinchart wrote: >>> Hi Sean, >>> >>> On Thursday 06 Oct 2016 15:53:28 Sean Paul wrote: >>>> On Thu, Oct 6, 2016 at 1:27 PM, Laurent Pinchart wrote: >>>>> 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 at kernel.org> >>>>>>>>> Signed-off-by: Maxime Ripard <maxime.ripard at free-electrons.com> >>>>>>>>> --- >>>>>>>>> .../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.tx >>>>>>>>> t >>>>>>>>> create mode 100644 drivers/gpu/drm/bridge/rgb-to-vga.c >>>>>>>>> >>>>>>>>> diff --git >>>>>>>>> a/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge. >>>>>>>>> txt >>>>>>>>> b/Documentation/devicetree/bindings/display/bridge/rgb-to-vga-bridge. >>>>>>>>> txt >>>>>>>>> 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. >>>> >>>> While we're bikeshedding (feel free to ignore my input on this), I >>>> think Maxime's initial "dumb" qualifier was better than "simple". >>> >>> I think I agree. >>> >>>> I think "passive" also gets the point across better than "simple", which >>>> we've already established as something else in drm. >>> >>> To my electrical engineer's ear, passive refers to a component or >>> combination >>> of components that is not capable of power gain. The resistors ladder VGA >>> DAC >>> that Maxime is trying to support is a passive system, but the ADV7123 VGA >>> DAC >>> that equally requires no configuration is an active component. >> >> If no one has any more objections within the next day, I'll pull in >> Maxime's v5 RGB to VGA bridge driver, and change the compatible to >> "dumb-vga-dac". > > That works for me. You'll probably want to update the Kconfig and file > name to match though.
Queued to drm-misc, with the changes suggested by you and Laurent. Thanks, Archit > > Maxime > -- Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project
