From 7cd8b54fd7b4a03e8a25107575dc547e219a3747 Mon Sep 17 00:00:00 2001
From: Eric Curtin <ecurtin@redhat.com>
Date: Fri, 17 Jun 2022 10:41:27 +0100
Subject: cam: kms_sink: Remove limitation that camera and display must match

There is a limitation that requires input and output to be pixel
for pixel identical in terms of height and width. Remove this
limitation to enable more hardware that doesn't match. Just start
drawing from top left 0, 0 corner.

Signed-off-by: Eric Curtin <ecurtin@redhat.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Tested-by: Eric Curtin <ecurtin@redhat.com>
---
 src/cam/kms_sink.cpp | 45 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 13 deletions(-)

diff --git a/src/cam/kms_sink.cpp b/src/cam/kms_sink.cpp
index 7add81a6..37a3bd50 100644
--- a/src/cam/kms_sink.cpp
+++ b/src/cam/kms_sink.cpp
@@ -11,6 +11,7 @@
 #include <algorithm>
 #include <assert.h>
 #include <iostream>
+#include <limits.h>
 #include <memory>
 #include <stdint.h>
 #include <string.h>
@@ -112,14 +113,32 @@ int KMSSink::configure(const libcamera::CameraConfiguration &config)
 
 	const libcamera::StreamConfiguration &cfg = config.at(0);
 
+	/* Find the best mode for the stream size. */
 	const std::vector<DRM::Mode> &modes = connector_->modes();
-	const auto iter = std::find_if(modes.begin(), modes.end(),
-				       [&](const DRM::Mode &mode) {
-					       return mode.hdisplay == cfg.size.width &&
-						      mode.vdisplay == cfg.size.height;
-				       });
-	if (iter == modes.end()) {
-		std::cerr << "No mode matching " << cfg.size << std::endl;
+
+	unsigned int cfgArea = cfg.size.width * cfg.size.height;
+	unsigned int bestDistance = UINT_MAX;
+
+	for (const DRM::Mode &mode : modes) {
+		unsigned int modeArea = mode.hdisplay * mode.vdisplay;
+		unsigned int distance = modeArea > cfgArea ? modeArea - cfgArea
+				      : cfgArea - modeArea;
+
+		if (distance < bestDistance) {
+			mode_ = &mode;
+			bestDistance = distance;
+
+			/*
+			 * If the sizes match exactly, there will be no better
+			 * match.
+			 */
+			if (distance == 0)
+				break;
+		}
+	}
+
+	if (!mode_) {
+		std::cerr << "No modes\n";
 		return -EINVAL;
 	}
 
@@ -127,7 +146,6 @@ int KMSSink::configure(const libcamera::CameraConfiguration &config)
 	if (ret < 0)
 		return ret;
 
-	mode_ = &*iter;
 	size_ = cfg.size;
 	stride_ = cfg.stride;
 
@@ -202,7 +220,8 @@ int KMSSink::configurePipeline(const libcamera::PixelFormat &format)
 	std::cout
 		<< "Using KMS plane " << plane_->id() << ", CRTC " << crtc_->id()
 		<< ", connector " << connector_->name()
-		<< " (" << connector_->id() << ")" << std::endl;
+		<< " (" << connector_->id() << "), mode " << mode_->hdisplay
+		<< "x" << mode_->vdisplay << "@" << mode_->vrefresh << std::endl;
 
 	return 0;
 }
@@ -295,12 +314,12 @@ bool KMSSink::processRequest(libcamera::Request *camRequest)
 		drmRequest->addProperty(plane_, "CRTC_ID", crtc_->id());
 		drmRequest->addProperty(plane_, "SRC_X", 0 << 16);
 		drmRequest->addProperty(plane_, "SRC_Y", 0 << 16);
-		drmRequest->addProperty(plane_, "SRC_W", mode_->hdisplay << 16);
-		drmRequest->addProperty(plane_, "SRC_H", mode_->vdisplay << 16);
+		drmRequest->addProperty(plane_, "SRC_W", size_.width << 16);
+		drmRequest->addProperty(plane_, "SRC_H", size_.height << 16);
 		drmRequest->addProperty(plane_, "CRTC_X", 0);
 		drmRequest->addProperty(plane_, "CRTC_Y", 0);
-		drmRequest->addProperty(plane_, "CRTC_W", mode_->hdisplay);
-		drmRequest->addProperty(plane_, "CRTC_H", mode_->vdisplay);
+		drmRequest->addProperty(plane_, "CRTC_W", size_.width);
+		drmRequest->addProperty(plane_, "CRTC_H", size_.height);
 
 		flags |= DRM::AtomicRequest::FlagAllowModeset;
 	}
-- 
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