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',

src/libcamera/gbm.cpp

@@ -0,0 +1,107 @@
+/* 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
+ */
+
+#include "libcamera/internal/gbm.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <linux/dma-buf.h>
+#include <linux/dma-heap.h>
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(GBM)
+
+/**
+ * \class GBM
+ * \brief Helper class for managing GBM interactions
+ *
+ * The GBM class provides a simplified interface for creating and managing
+ * GBM devices. It handles the initialization and teardown of GBM devices
+ * used for buffer allocation in graphics and camera pipelines.
+ *
+ * This class is responsible for opening a DRI render node, creating a GBM
+ * device, and providing access to the device and its associated pixel format.
+ */
+
+/**
+ *\var GBM::fd_
+ *\brief file descriptor to DRI device
+ */
+
+/**
+ *\var GBM::gbmDevice_
+ *\brief Pointer to GBM device structure derived from fd_
+ */
+
+/**
+ *\var GBM::format_
+ *\brief Pixel format the GBM surface was created in
+ */
+
+/**
+ *\brief GBM constructor.
+ *
+ * Creates a GBM instance with uninitialised state.
+ */
+GBM::GBM()
+{
+}
+
+/**
+ *\brief GBM destructor
+ *
+ * Cleans up the GBM device if it was successfully created, and closes
+ * the associated file descriptor.
+ */
+GBM::~GBM()
+{
+	if (gbmDevice_)
+		gbm_device_destroy(gbmDevice_);
+}
+
+/**
+ * \brief Create and initialize a GBM device
+ *
+ * \todo Get dri device name from envOption setting
+ *
+ * Opens the DRI render node (/dev/dri/renderD128) and creates a GBM
+ * device using the libgbm library. Sets the default pixel format to
+ * ARGB8888.
+ *
+ * \return 0 on success, or a negative error code on failure
+ */
+int GBM::createDevice()
+{
+	const char dri_node[] = "/dev/dri/renderD128";
+
+	int fd = open(dri_node, O_RDWR | O_CLOEXEC | O_NOCTTY);
+	if (fd < 0) {
+		LOG(GBM, Error) << "Open " << dri_node << " fail " << strerror(errno);
+		return -errno;
+	}
+	fd_ = UniqueFD(fd);
+
+	gbmDevice_ = gbm_create_device(fd_.get());
+	if (!gbmDevice_) {
+		LOG(GBM, Error) << "gbm_create_device fail" << strerror(errno);
+		return -errno;
+	}
+
+	format_ = libcamera::formats::ARGB8888;
+
+	return 0;
+}
+
+} /* namespace libcamera */

src/libcamera/meson.build

@@ -70,6 +70,15 @@ libcamera_deps = []
 libatomic = cc.find_library('atomic', required : false)
 libthreads = dependency('threads')
 
+libgbm = dependency('gbm', required : false)
+gbm_works = cc.check_header('gbm.h', required: false)
+
+if libgbm.found() and gbm_works
+    libcamera_internal_sources += files([
+        'gbm.cpp',
+    ])
+endif
+
 subdir('base')
 subdir('converter')
 subdir('ipa')
@@ -178,6 +187,7 @@ libcamera_deps += [
     libcamera_base_private,
     libcrypto,
     libdl,
+    libgbm,
     liblttng,
     libudev,
     libyaml,