From: laurent.pinchart@ideasonboard.com (Laurent Pinchart)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v5 2/5] drm/bridge: Add RGB to VGA bridge support
Date: Thu, 06 Oct 2016 20:27:39 +0300 [thread overview]
Message-ID: <5319260.UeCnJXKVPe@avalon> (raw)
In-Reply-To: <96cef428-19e5-ff98-1de1-fa31dd8d4142@codeaurora.org>
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@kernel.org>
> >>> Signed-off-by: Maxime Ripard <maxime.ripard@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.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
next prev parent reply other threads:[~2016-10-06 17:27 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-30 14:37 No subject Maxime Ripard
2016-09-30 14:37 ` [PATCH v5 1/5] drm/sun4i: rgb: Remove the bridge enable/disable functions Maxime Ripard
2016-09-30 14:37 ` [PATCH v5 2/5] drm/bridge: Add RGB to VGA bridge support Maxime Ripard
2016-10-03 11:10 ` Archit Taneja
2016-10-06 7:21 ` Maxime Ripard
2016-10-06 11:39 ` Archit Taneja
2016-10-06 17:27 ` Laurent Pinchart [this message]
2016-10-06 19:53 ` Sean Paul
2016-10-06 21:04 ` Laurent Pinchart
2016-10-07 4:57 ` Archit Taneja
2016-10-07 9:14 ` Maxime Ripard
2016-10-10 5:35 ` Archit Taneja
2016-10-10 7:15 ` Laurent Pinchart
2016-10-10 9:34 ` Archit Taneja
2016-10-07 9:28 ` Laurent Pinchart
2016-10-07 13:42 ` Laurent Pinchart
2016-09-30 14:37 ` [PATCH v5 3/5] ARM: sun5i: a13-olinuxino: Enable VGA bridge Maxime Ripard
2016-09-30 14:37 ` [PATCH v5 4/5] ARM: multi_v7: enable " Maxime Ripard
2016-09-30 14:37 ` [PATCH v5 5/5] ARM: sunxi: Enable " Maxime Ripard
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5319260.UeCnJXKVPe@avalon \
--to=laurent.pinchart@ideasonboard.com \
--cc=linux-arm-kernel@lists.infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).