drm显示一张图片5秒钟代码

下面是使用DRM显示一张图片5秒钟的代码：

#include <fcntl.h>
#include <drm/drm.h>
#include <drm/drm_fourcc.h>
#include <drm/drm_mode.h>
#include <sys/mman.h>
#include <unistd.h>

int main() {
    int fd = open("/dev/dri/card0", O_RDWR);
    if (fd < 0) {
        perror("open failed");
        return -1;
    }

    drmModeRes *resources = drmModeGetResources(fd);
    if (!resources) {
        perror("drmModeGetResources failed");
        close(fd);
        return -1;
    }

    drmModeConnector *connector = NULL;
    drmModeEncoder *encoder = NULL;
    for (int i = 0; i < resources->count_connectors; i++) {
        connector = drmModeGetConnector(fd, resources->connectors[i]);
        if (connector->connection == DRM_MODE_CONNECTED) {
            for (int j = 0; j < connector->count_encoders; j++) {
                encoder = drmModeGetEncoder(fd, connector->encoders[j]);
                if (encoder->encoder_id == connector->encoder_id) {
                    break;
                }
                drmModeFreeEncoder(encoder);
                encoder = NULL;
            }
            break;
        }
        drmModeFreeConnector(connector);
        connector = NULL;
    }

    drmModeCrtc *crtc = drmModeGetCrtc(fd, encoder->crtc_id);
    uint32_t fb_id = 0;
    uint32_t width = crtc->mode.hdisplay;
    uint32_t height = crtc->mode.vdisplay;
    uint32_t bpp = 32;
    uint32_t pitch = width * bpp / 8;
    uint32_t size = pitch * height;
    uint8_t *buffer = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
    if (buffer == MAP_FAILED) {
        perror("mmap failed");
        drmModeFreeCrtc(crtc);
        drmModeFreeEncoder(encoder);
        drmModeFreeConnector(connector);
        drmModeFreeResources(resources);
        close(fd);
        return -1;
    }

    int image_fd = open("image.raw", O_RDONLY);
    if (image_fd < 0) {
        perror("open image file failed");
        munmap(buffer, size);
        drmModeFreeCrtc(crtc);
        drmModeFreeEncoder(encoder);
        drmModeFreeConnector(connector);
        drmModeFreeResources(resources);
        close(fd);
        return -1;
    }
    ssize_t ret = read(image_fd, buffer, size);
    if (ret != size) {
        perror("read image file failed");
        close(image_fd);
        munmap(buffer, size);
        drmModeFreeCrtc(crtc);
        drmModeFreeEncoder(encoder);
        drmModeFreeConnector(connector);
        drmModeFreeResources(resources);
        close(fd);
        return -1;
    }
    close(image_fd);

    drmModeAddFB(fd, width, height, bpp, bpp, pitch, (uint32_t*)buffer, &fb_id);

    drmModeSetCrtc(fd, encoder->crtc_id, fb_id, 0, 0, &connector->connector_id, 1, &crtc->mode);

    sleep(5);

    drmModeRmFB(fd, fb_id);

    drmModeSetCrtc(fd, crtc->crtc_id, crtc->buffer_id, crtc->x, crtc->y, &connector->connector_id, 1, &crtc->mode);

    munmap(buffer, size);
    drmModeFreeCrtc(crtc);
    drmModeFreeEncoder(encoder);
    drmModeFreeConnector(connector);
    drmModeFreeResources(resources);
    close(fd);

    return 0;
}

这段代码首先打开DRM设备文件`/dev/dri/card0`，然后获取DRM设备的资源、连接器、编码器和CRTC等信息。接着，它通过`mmap`函数映射一块内存作为显存，并从文件中读取一张图片到这块内存中。然后，它使用`drmModeAddFB`函数创建一个帧缓冲区，并将这个帧缓冲区绑定到CRTC上，显示图片。最后，它等待5秒钟，然后删除帧缓冲区，并将CRTC恢复到原始状态。