libcamera: software_isp: gbm: Add 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 GPU when making a texture for the Debayer
vertex/fragment shaders and thus ensure we receive an uncompressed and
untiled output buffer.

Acked-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Robert Mader <robert.mader@collabora.com>
Tested-by: Robert Mader <robert.mader@collabora.com>
Tested-by: Hans de Goede <johannes.goede@oss.qualcomm.com> # ThinkPad T14s gen 6 (arm64) ov02c10 + X1c gen 12 ov08x40
Tested-by: Kieran Bingham <kieran.bingham@ideasonboard.com> # Lenovo X13s
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

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>
+ *
+ * Helper class for managing GBM interactions
+ */
+
+#pragma once
+
+#include <gbm.h>
+
+#include <libcamera/base/log.h>
+#include <libcamera/base/unique_fd.h>
+
+#include <libcamera/formats.h>
+
+namespace libcamera {
+
+LOG_DECLARE_CATEGORY(GBM)
+
+class GBM
+{
+public:
+	GBM();
+	~GBM();
+
+	int createDevice();
+
+	/**
+	 * \brief Retrieve the GBM device handle
+	 *
+	 * \return Pointer to the gbm_device structure, or nullptr if the device
+	 * has not been created
+	 */
+	struct gbm_device *device() const { return gbmDevice_; }
+
+	/**
+	 * \brief Retrieve the pixel format
+	 *
+	 * \return The PixelFormat used by this GBM instance (ARGB8888)
+	 */
+	PixelFormat format() const { return format_; }
+
+private:
+	LIBCAMERA_DISABLE_COPY_AND_MOVE(GBM)
+
+	UniqueFD fd_;
+	struct gbm_device *gbmDevice_ = nullptr;
+	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',
     'global_configuration.h',
     'ipa_data_serializer.h',
     'ipa_manager.h',