掌機 - Miyoo Flip - C/C++ - DRM/KMS - OpenGL ES 2.0 - Screen Tearing Test

參考資訊：
https://gist.github.com/dvdhrm/5083553
https://www.kernel.org/doc/html/v4.15/gpu/drm-kms.html
https://github.com/grate-driver/libdrm/blob/master/xf86drmMode.h
https://gist.github.com/Miouyouyou/89e9fe56a2c59bce7d4a18a858f389ef

main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <time.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <gbm.h>
#include <xf86drm.h>
#include <xf86drmMode.h>
#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>
#include <EGL/egl.h>
#include <EGL/eglext.h>
 
static int fd = -1;
static int fb = -1;
static int pre_fb = 0;
static struct gbm_bo *pre_bo = NULL; 
static drmModeRes *res = NULL;
static drmModeCrtc *crtc = NULL;
static drmModeEncoder *enc = NULL;
static drmModeConnector *conn = NULL;
 
const char *vShaderSrc = "void main(void){}";
const char *fShaderSrc = "void main(void){}";
 
int main(int argc, char *argv[])
{
    const int w = 640;
    const int h = 480;
    const int bpp = 32;
    const int depth = 24;
  
    int i = 0;
    int j = 0;
  
    fd = open("/dev/dri/card0", O_RDWR | O_CLOEXEC);
    res = drmModeGetResources(fd);
    conn = drmModeGetConnector(fd, res->connectors[1]);
    enc = drmModeGetEncoder(fd, res->encoders[2]);
    crtc = drmModeGetCrtc(fd, res->crtcs[1]);
 
    struct gbm_device *gbm = gbm_create_device(fd);
    struct gbm_surface *gs = gbm_surface_create(gbm, crtc->mode.hdisplay, crtc->mode.vdisplay, GBM_FORMAT_XRGB8888, GBM_BO_USE_SCANOUT | GBM_BO_USE_RENDERING);
 
    EGLint egl_major = 0;
    EGLint egl_minor = 0;
    EGLint num_configs = 0;
    EGLConfig configs = {0};
    EGLDisplay display = EGL_NO_DISPLAY;
    EGLSurface surface = EGL_NO_SURFACE;
    EGLContext context = EGL_NO_CONTEXT;
    EGLint config_attribs[] = {
        EGL_SURFACE_TYPE,    EGL_WINDOW_BIT,
        EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
        EGL_RED_SIZE,   1,  
        EGL_GREEN_SIZE, 1,
        EGL_BLUE_SIZE,  1,  
        EGL_ALPHA_SIZE, 0,
        EGL_NONE
    };
    EGLint const context_attributes[] = {
        EGL_CONTEXT_CLIENT_VERSION, 2,
        EGL_NONE,
    };
    GLuint vShader = 0;
    GLuint fShader = 0;
    GLuint pObject = 0;
    GLint compiled = 0;
 
    PFNEGLGETPLATFORMDISPLAYEXTPROC get_platform_display = NULL;
    get_platform_display = (void *)eglGetProcAddress("eglGetPlatformDisplayEXT");
    display = get_platform_display(EGL_PLATFORM_GBM_KHR, gbm, NULL);
    eglInitialize(display, &egl_major, &egl_minor);
    eglBindAPI(EGL_OPENGL_ES_API);
    eglChooseConfig(display, config_attribs, &configs, 1, &num_configs);
    surface = eglCreateWindowSurface(display, configs, gs, NULL);
    context = eglCreateContext(display, configs, EGL_NO_CONTEXT, context_attributes);
    eglMakeCurrent(display, surface, surface, context);
   
    vShader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vShader, 1, &vShaderSrc, NULL);
    glCompileShader(vShader);
    glGetShaderiv(vShader, GL_COMPILE_STATUS, &compiled);
   
    fShader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fShader, 1, &fShaderSrc, NULL);
    glCompileShader(fShader);
    glGetShaderiv(fShader, GL_COMPILE_STATUS, &compiled);
    
    pObject = glCreateProgram();
    glAttachShader(pObject, vShader);
    glAttachShader(pObject, fShader);
    glLinkProgram(pObject);
    glUseProgram(pObject);
   
    glViewport(0, 0, w, h);

    uint32_t cc = 0;
    while (1) {
        switch (cc++ % 3) {
        case 0:
            glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
            break;
        case 1:
            glClearColor(0.0f, 1.0f, 0.0f, 1.0f);
            break;
        case 2:
            glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
            break;
        }
        glClear(GL_COLOR_BUFFER_BIT);
        eglSwapBuffers(display, surface);
    
        struct gbm_bo *bo = gbm_surface_lock_front_buffer(gs);
        drmModeAddFB(fd, w, h, depth, bpp, gbm_bo_get_stride(bo), gbm_bo_get_handle(bo).u32, &fb);
        drmModeSetCrtc(fd, crtc->crtc_id, fb, 0, 0, (uint32_t *)conn, 1, &crtc->mode);
        if (pre_bo) {
            drmModeRmFB(fd, pre_fb);
            gbm_surface_release_buffer(gs, pre_bo);
        }
        pre_bo = bo;
        pre_fb = fb;
    }
 
    eglMakeCurrent(display, EGL_NO_SURFACE, EGL_NO_SURFACE, EGL_NO_CONTEXT);
    eglDestroyContext(display, context);
    eglDestroySurface(display, surface);
 
    drmModeRmFB(fd, fb); 
    drmModeFreeCrtc(crtc);
    drmModeFreeEncoder(enc);
    drmModeFreeConnector(conn);
    drmModeFreeResources(res);
    close(fd);
    return 0;
}