From 5f3f95c67d86cf82ae32d6821b283724eba8b293 Mon Sep 17 00:00:00 2001
From: PancakeTAS <pancake@mgnet.work>
Date: Tue, 23 Jun 2026 21:12:55 +0200
Subject: Implement GEM objects and dumb buffers

---
 src/gem.cpp | 134 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 src/gem.cpp

(limited to 'src')

diff --git a/src/gem.cpp b/src/gem.cpp
new file mode 100644
index 0000000..4b81703
--- /dev/null
+++ b/src/gem.cpp
@@ -0,0 +1,134 @@
+/* SPDX-License-Identifier: MIT */
+
+#include "drm++/gem.hpp"
+#include "drm++/helper.hpp"
+#include "drm++/ioctl.hpp"
+
+#include <cerrno>
+#include <system_error>
+
+#include <drm.h>
+#include <drm_mode.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+using namespace drm;
+using namespace drm::gem;
+
+/* GEM object class */
+
+Object::Object(int fd, int dmabuf_fd, bool close) : m_fd(fd) {
+    try {
+        drm_prime_handle args{
+            .fd = dmabuf_fd
+        };
+        ioctl::perform(this->m_fd, DRM_IOCTL_PRIME_FD_TO_HANDLE, args);
+
+        this->m_handle = args.handle;
+    } catch (...) {
+        if (close) {
+            ::close(dmabuf_fd);
+        }
+
+        throw;
+    }
+
+    if (close) {
+        ::close(dmabuf_fd);
+    }
+}
+
+int Object::exportFd(ExportFlags flags) const {
+    drm_prime_handle args{
+        .handle = this->m_handle,
+        .flags = static_cast<u32>(flags)
+    };
+    ioctl::perform(this->m_fd, DRM_IOCTL_PRIME_HANDLE_TO_FD, args);
+
+    return args.fd;
+}
+
+void Object::changeHandle(u32 handle) {
+    drm_gem_close args{
+        .handle = this->m_handle
+    };
+    ioctl::perform(this->m_fd, DRM_IOCTL_GEM_CLOSE, args);
+
+    this->m_handle = handle;
+}
+
+void Object::destruct() noexcept {
+    if (this->m_fd < 0) {
+        return;
+    }
+
+    drm_gem_close args{
+        .handle = this->m_handle
+    };
+    try {
+        ioctl::perform(this->m_fd, DRM_IOCTL_GEM_CLOSE, args);
+    } catch(...) {
+        (void) 0; // not much we can do about the leak
+    }
+
+    this->m_fd = -1;
+}
+
+/* Dumb buffer class */
+
+DumbBuffer::DumbBuffer(int fd, u32 width, u32 height, u32 bpp)
+        : Object(fd, -1), m_width(width), m_height(height), m_bpp(bpp) {
+    drm_mode_create_dumb args{
+        .height = height,
+        .width = width,
+        .bpp = bpp
+    };
+    ioctl::perform(this->m_fd, DRM_IOCTL_MODE_CREATE_DUMB, args);
+
+    this->m_handle = args.handle;
+    this->m_pitch = args.pitch;
+    this->m_size = args.size;
+}
+
+void* DumbBuffer::map() {
+    if (this->m_map != nullptr) {
+        return this->m_map;
+    }
+
+    drm_mode_map_dumb args{
+        .handle = this->m_handle
+    };
+    ioctl::perform(this->m_fd, DRM_IOCTL_MODE_MAP_DUMB, args);
+
+    void* map{::mmap(nullptr, this->m_size, PROT_READ | PROT_WRITE, MAP_SHARED,
+        this->m_fd, static_cast<off_t>(args.offset))};
+    if (map == MAP_FAILED) {
+        throw std::system_error(errno, std::generic_category(), "mmap failed");
+    }
+
+    this->m_map = map;
+    return this->m_map;
+}
+
+void DumbBuffer::destruct() noexcept {
+    if (this->m_fd < 0) {
+        return;
+    }
+
+    if (this->m_map != nullptr) {
+        ::munmap(this->m_map, this->m_size);
+        this->m_map = nullptr;
+    }
+
+    drm_mode_destroy_dumb args{
+        .handle = this->m_handle
+    };
+    try {
+        ioctl::perform(this->m_fd, DRM_IOCTL_MODE_DESTROY_DUMB, args);
+    } catch(...) {
+        (void) 0; // not much we can do about the leak
+    }
+
+    this->m_fd = -1;
+}
-- 
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