libcamera: software_isp: gbm: Add in a GBM helper class for GPU surface access

A helper class to interact with GBM. This will allow us to specify the
internal storage format of the CPU when making a texture for the Debayer
vertext/fragment shaders and thus ensure we receive an uncompressed and
untiled output buffer.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>

include/libcamera/internal/gbm.h

@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Linaro Ltd.
+ *
+ * Authors:
+ * Bryan O'Donoghue <bryan.odonoghue@linaro.org>
+ *
+ * gbm.h - Helper class for managing GBM interactions.
+ */
+
+#pragma once
+
+#include <gbm.h>
+
+#include <libcamera/base/log.h>
+
+#include <libcamera/formats.h>
+
+namespace libcamera {
+
+LOG_DECLARE_CATEGORY(GBM)
+
+class GBM
+{
+public:
+	GBM();
+	~GBM();
+
+	int initSurface(uint32_t width, uint32_t height);
+	int mapSurface();
+	int getFrameBufferData(uint8_t *data_out, size_t data_len);
+	struct gbm_device *getDevice() { return gbm_device_; }
+	struct gbm_surface *getSurface() { return gbm_surface_; }
+	uint32_t getFrameSize() { return framesize_; }
+	uint32_t getStride() { return stride_; }
+	PixelFormat getPixelFormat() { return format_; }
+
+private:
+	int fd_;
+	struct gbm_device *gbm_device_;
+	struct gbm_surface *gbm_surface_;
+
+	struct gbm_bo *gbm_bo_;
+	uint32_t width_;
+	uint32_t height_;
+	uint32_t stride_;
+	uint32_t offset_;
+	uint32_t framesize_;
+	void *map_;
+	int bo_fd_;
+
+	PixelFormat format_;
+};
+
+} // namespace libcamera

include/libcamera/internal/meson.build

@@ -23,6 +23,7 @@ libcamera_internal_headers = files([
     'dma_buf_allocator.h',
     'formats.h',
     'framebuffer.h',
+    'gbm.h',
     'ipa_data_serializer.h',
     'ipa_manager.h',
     'ipa_module.h',