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',

src/libcamera/gbm.cpp

@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Linaro Ltd.
+ *
+ * Authors:
+ * Bryan O'Donoghue <bryan.odonoghue@linaro.org>
+ *
+ * egl.cpp - Helper class for managing GBM interactions.
+ */
+
+#include "libcamera/internal/gbm.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)
+
+GBM::GBM()
+{
+	fd_ = 0;
+}
+
+GBM::~GBM()
+{
+	if (gbm_surface_)
+		gbm_surface_destroy(gbm_surface_);
+
+	if (gbm_device_)
+		gbm_device_destroy(gbm_device_);
+
+	if (fd_ >= 0)
+		close(fd_);
+}
+
+// this should probably go into its own class to deal with the
+// allocation and deletion of frambuffers attached to GBM devices/objects
+int GBM::initSurface(uint32_t width, uint32_t height)
+{
+	const char *dri_node = "/dev/dri/renderD128"; //TODO: get from an env or config setting
+
+	fd_ = open(dri_node, O_RDWR | O_CLOEXEC); //TODO: CLOEXEC ?
+	if (fd_ < 0) {
+		LOG(GBM, Error) << "Open " << dri_node << " fail " << fd_;
+		return fd_;
+	}
+
+	gbm_device_ = gbm_create_device(fd_);
+	if (!gbm_device_) {
+		LOG(GBM, Error) << "gbm_crate_device fail";
+		goto fail;
+	}
+
+	// GBM_FORMAT_RGBA8888 is not supported mesa::src/gbm/dri/gbm_dri.c::gbm_dri_visuals_table[]
+	// This means we need to choose XRGB8888 or ARGB8888 as the raw buffer format
+	gbm_surface_ = gbm_surface_create(gbm_device_, width, height, GBM_FORMAT_ARGB8888,
+					  GBM_BO_USE_RENDERING | GBM_BO_USE_LINEAR);
+	if (!gbm_surface_) {
+		LOG(GBM, Error) << "Unable to create linear gbm surface";
+		goto fail;
+	}
+
+	format_ = libcamera::formats::ARGB8888;
+
+	return 0;
+fail:
+	return -ENODEV;
+}
+
+int GBM::mapSurface()
+{
+	gbm_bo_ = gbm_surface_lock_front_buffer(gbm_surface_);
+	if (!gbm_bo_) {
+		LOG(GBM, Error) << "GBM input buffer object create fail";
+		return -ENODEV;
+	}
+	gbm_surface_release_buffer(gbm_surface_, gbm_bo_);
+
+	bo_fd_ = gbm_bo_get_fd(gbm_bo_);
+
+	if (!bo_fd_) {
+		gbm_surface_release_buffer(gbm_surface_, gbm_bo_);
+		LOG(GBM, Error) << "Unable to get fd for bo: " << bo_fd_;
+		return -ENODEV;
+	}
+
+	stride_ = gbm_bo_get_stride(gbm_bo_);
+	width_ = gbm_bo_get_width(gbm_bo_);
+	height_ = gbm_bo_get_height(gbm_bo_);
+	offset_ = gbm_bo_get_offset(gbm_bo_, 0);
+	framesize_ = height_ * stride_;
+
+	map_ = mmap(NULL, height_ * stride_, PROT_READ, MAP_SHARED, bo_fd_, 0);
+	if (map_ == MAP_FAILED) {
+		LOG(GBM, Error) << "mmap gbm_bo_ fail";
+		return -ENODEV;
+	}
+
+	LOG(GBM, Debug) << " stride " << stride_
+			<< " width " << width_
+			<< " height " << height_
+			<< " offset " << offset_
+			<< " framesize " << framesize_;
+
+	return 0;
+}
+
+int GBM::getFrameBufferData(uint8_t *data, size_t data_len)
+{
+	struct dma_buf_sync sync;
+
+	gbm_surface_lock_front_buffer(gbm_surface_);
+
+	sync.flags = DMA_BUF_SYNC_START | DMA_BUF_SYNC_READ;
+	ioctl(bo_fd_, DMA_BUF_IOCTL_SYNC, &sync);
+
+	if (data_len > framesize_) {
+		LOG(GBM, Error) << "Invalid read size " << data_len << " max is " << framesize_;
+		return -EINVAL;
+	}
+
+	memcpy(data, map_, data_len);
+
+	sync.flags = DMA_BUF_SYNC_END | DMA_BUF_SYNC_READ;
+	ioctl(bo_fd_, DMA_BUF_IOCTL_SYNC, &sync);
+
+	gbm_surface_release_buffer(gbm_surface_, gbm_bo_);
+
+	return 0;
+}
+} //namespace libcamera

src/libcamera/meson.build

@@ -67,6 +67,16 @@ libcamera_deps = []
 libatomic = cc.find_library('atomic', required : false)
 libthreads = dependency('threads')
 
+libgbm = cc.find_library('gbm', required: false)
+gbm_works = cc.check_header('gbm.h', required: false) 
+
+if libgbm.found() and gbm_works
+    config_h.set('HAVE_GBM', 1)
+    libcamera_internal_sources += files([
+        'gbm.cpp',
+    ])
+endif
+
 subdir('base')
 subdir('converter')
 subdir('ipa')
@@ -188,6 +198,7 @@ libcamera_deps += [
     libcamera_base_private,
     libcrypto,
     libdl,
+    libgbm,
     liblttng,
     libudev,
     libyaml,