使用drm的over_plane的示例C语言代码

以下是一个使用 DRM 的 `over_plane` 的示例 C 代码。它需要 Linux 系统和 DRM 库：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/mman.h>
#include <xf86drm.h>
#include <xf86drmMode.h>

#define BO_SIZE (4096 * 4096 * 4)

int main() {
    int drm_fd = open("/dev/dri/card0", O_RDWR);
    if (drm_fd < 0) {
        fprintf(stderr, "Failed to open DRM device: %s\n", strerror(errno));
        return 1;
    }

    // Get the primary plane id
    drmModeRes *resources = drmModeGetResources(drm_fd);
    if (!resources) {
        fprintf(stderr, "Failed to get DRM resources: %s\n", strerror(errno));
        close(drm_fd);
        return 1;
    }
    int plane_id = -1;
    for (int i = 0; i < resources->count_planes; i++) {
        drmModePlane *plane = drmModeGetPlane(drm_fd, resources->planes[i]);
        if (plane && (plane->possible_crtcs & (1 << 0))) {
            plane_id = plane->plane_id;
            drmModeFreePlane(plane);
            break;
        }
        drmModeFreePlane(plane);
    }
    if (plane_id == -1) {
        fprintf(stderr, "Failed to find primary plane\n");
        drmModeFreeResources(resources);
        close(drm_fd);
        return 1;
    }

    // Create a buffer object
    uint32_t handle;
    int ret = drmPrimeHandleToFD(drm_fd, handle, 0, &handle);
    if (ret < 0) {
        fprintf(stderr, "Failed to prime handle: %s\n", strerror(errno));
        drmModeFreeResources(resources);
        close(drm_fd);
        return 1;
    }
    uint32_t pitch = BO_SIZE / 4;
    uint32_t bo_handles[4] = {handle, 0, 0, 0};
    uint32_t bo_pitches[4] = {pitch, 0, 0, 0};
    uint32_t bo_offsets[4] = {0, 0, 0, 0};
    uint32_t bo_flags = 0;
    uint32_t buffer_id;
    ret = drmModeAddFB2(drm_fd, 4096, 4096, DRM_FORMAT_ARGB8888, bo_handles, bo_pitches, bo_offsets, &buffer_id, bo_flags);
    if (ret < 0) {
        fprintf(stderr, "Failed to create buffer object: %s\n", strerror(errno));
        close(handle);
        drmModeFreeResources(resources);
        close(drm_fd);
        return 1;
    }

    // Set the plane
    drmModePlane *plane = drmModeGetPlane(drm_fd, plane_id);
    if (!plane) {
        fprintf(stderr, "Failed to get primary plane: %s\n", strerror(errno));
        drmModeRmFB(drm_fd, buffer_id);
        close(handle);
        drmModeFreeResources(resources);
        close(drm_fd);
        return 1;
    }
    ret = drmModeSetPlane(drm_fd, plane_id, 0, 0, 0, 0, 0, 4096, 4096, 0, buffer_id, 0, 0, 0);
    if (ret < 0) {
        fprintf(stderr, "Failed to set plane: %s\n", strerror(errno));
        drmModeFreePlane(plane);
        drmModeRmFB(drm_fd, buffer_id);
        close(handle);
        drmModeFreeResources(resources);
        close(drm_fd);
        return 1;
    }
    drmModeFreePlane(plane);

    // Wait for input
    printf("Press Enter to exit...\n");
    getchar();

    // Clear the plane
    ret = drmModeSetPlane(drm_fd, plane_id, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
    if (ret < 0) {
        fprintf(stderr, "Failed to clear plane: %s\n", strerror(errno));
    }

    // Cleanup
    drmModeRmFB(drm_fd, buffer_id);
    close(handle);
    drmModeFreeResources(resources);
    close(drm_fd);

    return 0;
}

此代码将使用 DRM 在屏幕上显示一个空白的 4096x4096 像素的矩形，并等待用户按下回车键后退出。