From 843048499fe1f1f8cea74838c1e3436945c1b1b7 Mon Sep 17 00:00:00 2001
From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Date: Sun, 5 Sep 2021 23:24:29 +0300
Subject: cam: drm: Support per-plane stride values

The stride is not always identical for all planes for multi-planar
formats. Semi-planar YUV formats without horizontal subsampling often
have a chroma stride equal to twice the luma stride, and tri-planar YUV
formats with a 1/2 horizontal subsampling often have a chroma stride
equal to half the luma stride. This isn't correctly taken into account
when creating a DRM frame buffer, as the same stride is set for all
planes.

libcamera doesn't report per-plane stride values yet, but uses chroma
strides that match the above description for all currently supported
platforms. Calculation the chrome strides appropriately in the KMSSink
class, and pass them to DRM::createFrameBuffer().

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
 src/cam/kms_sink.cpp | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

(limited to 'src/cam/kms_sink.cpp')

diff --git a/src/cam/kms_sink.cpp b/src/cam/kms_sink.cpp
index 8c0b79c6..658192ef 100644
--- a/src/cam/kms_sink.cpp
+++ b/src/cam/kms_sink.cpp
@@ -7,10 +7,12 @@
 
 #include "kms_sink.h"
 
+#include <array>
 #include <algorithm>
 #include <assert.h>
 #include <iostream>
 #include <memory>
+#include <stdint.h>
 #include <string.h>
 
 #include <libcamera/camera.h>
@@ -65,8 +67,32 @@ KMSSink::KMSSink(const std::string &connectorName)
 
 void KMSSink::mapBuffer(libcamera::FrameBuffer *buffer)
 {
+	std::array<uint32_t, 4> strides = {};
+
+	/* \todo Should libcamera report per-plane strides ? */
+	unsigned int uvStrideMultiplier;
+
+	switch (format_) {
+	case libcamera::formats::NV24:
+	case libcamera::formats::NV42:
+		uvStrideMultiplier = 4;
+		break;
+	case libcamera::formats::YUV420:
+	case libcamera::formats::YVU420:
+	case libcamera::formats::YUV422:
+		uvStrideMultiplier = 1;
+		break;
+	default:
+		uvStrideMultiplier = 2;
+		break;
+	}
+
+	strides[0] = stride_;
+	for (unsigned int i = 1; i < buffer->planes().size(); ++i)
+		strides[i] = stride_ * uvStrideMultiplier / 2;
+
 	std::unique_ptr<DRM::FrameBuffer> drmBuffer =
-		dev_.createFrameBuffer(*buffer, format_, size_, stride_);
+		dev_.createFrameBuffer(*buffer, format_, size_, strides);
 	if (!drmBuffer)
 		return;
 
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