[libcamera-devel] [PATCH v3] cam: kms_sink: Remove limitation that camera and display must match

[Eric Curtin]

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 right 0, 0 corner.

Signed-off-by: Eric Curtin <ecurtin at redhat.com>
---
Changes in v2:
- Tested and support drawing from negative pixel range
  kernel parameter (video=960x540 at 60) was useful here
Changes in v3:
- Much simplified version of the patch where we just attempt to
  draw from point 0, 0. Only in the case where we do not find a
  matching mode. Can expand to do centralization, scaling, etc.
  in further patches if needs be.
---
 src/cam/kms_sink.cpp | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/src/cam/kms_sink.cpp b/src/cam/kms_sink.cpp
index da579846..5847c4e1 100644
--- a/src/cam/kms_sink.cpp
+++ b/src/cam/kms_sink.cpp
@@ -119,17 +119,21 @@ int KMSSink::configure(const libcamera::CameraConfiguration &config)
 						      mode.vdisplay == cfg.size.height;
 				       });
 	if (iter == modes.end()) {
-		std::cerr
-			<< "No mode matching " << cfg.size.toString()
-			<< std::endl;
-		return -EINVAL;
+                if (modes.empty()) {
+        		std::cerr << "No modes\n";
+        		return -EINVAL;
+                }
+
+                mode_ = &modes[0];
 	}
+        else {
+                mode_ = &*iter;
+        }
 
 	int ret = configurePipeline(cfg.pixelFormat);
 	if (ret < 0)
 		return ret;
 
-	mode_ = &*iter;
 	size_ = cfg.size;
 	stride_ = cfg.stride;
 
@@ -297,12 +301,12 @@ 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;
 	}
-- 
2.35.1