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Simple DirectMedia Layer
Copyright (C) 1997-2020 Sam Lantinga <>
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
#include "../../SDL_internal.h"
#include "SDL_kmsdrmvideo.h"
#include "SDL_kmsdrmopengles.h"
#include "SDL_kmsdrmdyn.h"
/* EGL implementation of SDL OpenGL support */
KMSDRM_GLES_LoadLibrary(_THIS, const char *path) {
NativeDisplayType display = (NativeDisplayType)((SDL_VideoData *)_this->driverdata)->gbm_dev;
return SDL_EGL_LoadLibrary(_this, path, display, EGL_PLATFORM_GBM_MESA);
int KMSDRM_GLES_SetSwapInterval(_THIS, int interval) {
if (!_this->egl_data) {
return SDL_SetError("EGL not initialized");
if (interval == 0 || interval == 1) {
_this->egl_data->egl_swapinterval = interval;
} else {
return SDL_SetError("Only swap intervals of 0 or 1 are supported");
return 0;
/* Atomic functions block */
#define VOID2U64(x) ((uint64_t)(unsigned long)(x))
static EGLSyncKHR create_fence(int fd, _THIS)
EGLint attrib_list[] = {
EGLSyncKHR fence = _this->egl_data->eglCreateSyncKHR(_this->egl_data->egl_display,
return fence;
KMSDRM_GLES_SwapWindow(_THIS, SDL_Window * window) {
SDL_WindowData *windata = ((SDL_WindowData *) window->driverdata);
SDL_DisplayData *dispdata = (SDL_DisplayData *) SDL_GetDisplayForWindow(window)->driverdata;
KMSDRM_FBInfo *fb;
EGLint status;
int ret;
uint32_t flags = DRM_MODE_ATOMIC_NONBLOCK;
EGLSyncKHR display_in_fence = NULL;
EGLSyncKHR display_out_fence = NULL;
/* Create the display in-fence, and export it as a fence fd to pass into the kernel. */
display_in_fence = create_fence(EGL_NO_NATIVE_FENCE_FD_ANDROID, _this);
dispdata->kms_in_fence_fd = _this->egl_data->eglDupNativeFenceFDANDROID(_this->egl_data->egl_display, display_in_fence);
/* Mark the back buffer as the next front buffer, and the current front buffer as elegible
by EGL as back buffer to draw into.
This will not really happen until we post the pageflip though KMS with the atomic ioctl
and it completes on next vsync. */
_this->egl_data->eglSwapBuffers(_this->egl_data->egl_display, windata->egl_surface);
/* Lock the buffer that is marked by eglSwapBuffers() to become the next front buffer (so it can not
be chosen by EGL as back buffer to draw on), and get a handle to it, so we can use that handle
to request the KMS pageflip that will set it as front buffer. */
windata->next_bo = KMSDRM_gbm_surface_lock_front_buffer(windata->gs);
if (!windata->next_bo) {
printf("Failed to lock frontbuffer\n");
return -1;
fb = KMSDRM_FBFromBO(_this, windata->next_bo);
if (!fb) {
printf("Failed to get a new framebuffer BO\n");
return -1;
* Issue atomic pageflip to post the pageflip thru KMS. Returns immediately.
* Never issue an atomic ioctl while the previuos one is pending: it will be rejected.
ret = drm_atomic_commit(_this, fb->fb_id, flags);
if (ret) {
printf("failed to do atomic commit\n");
return -1;
/* Get the display out fence, returned by the atomic ioctl. */
display_out_fence = create_fence(dispdata->kms_out_fence_fd, _this);
/* Wait on the CPU side for the _previous_ commit to complete before we post the flip through KMS,
* because atomic will reject the commit if we post a new one while the previous one is still pending. */
do {
status = _this->egl_data->eglClientWaitSyncKHR(_this->egl_data->egl_display, display_out_fence, 0, EGL_FOREVER_KHR);
} while (status != EGL_CONDITION_SATISFIED_KHR);
/* Destroy both in and out display fences. */
_this->egl_data->eglDestroySyncKHR(_this->egl_data->egl_display, display_out_fence);
_this->egl_data->eglDestroySyncKHR(_this->egl_data->egl_display, display_in_fence);
/* Now that the pageflip is complete, release last front buffer so EGL can chose it
* as back buffer and render on it again: */
if (windata->curr_bo) {
KMSDRM_gbm_surface_release_buffer(windata->gs, windata->curr_bo);
windata->curr_bo = NULL;
/* Take note of the current front buffer, so it can be freed next time this function is called. */
windata->curr_bo = windata->next_bo;
return ret;
/* End of Atomic functions block */
/* vi: set ts=4 sw=4 expandtab: */