drm显示指定图片代码

以下是使用DRM显示指定图片的基本代码示例：

#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <linux/fb.h>
#include <linux/drm.h>
#include <linux/drm_mode.h>

#define DEVICE_NAME "/dev/dri/card0"
#define FB_DEVICE "/dev/fb0"

int main()
{
    int fd, fb_fd;
    drmModeRes *resources;
    drmModeConnector *connector = NULL;
    drmModeEncoder *encoder;
    drmModeModeInfo mode;
    uint32_t connector_id, encoder_id, crtc_id;
    struct drm_set_client_cap cap = {DRM_CLIENT_CAP_UNIVERSAL_PLANES, 1};
    struct drm_mode_create_dumb create;
    struct drm_mode_map_dumb map;
    struct drm_mode_fb_cmd fcmd;
    struct fb_var_screeninfo var_info;
    void *fb_map = NULL;
    uint32_t *buf = NULL;

    // 打开DRM设备
    fd = open(DEVICE_NAME, O_RDWR);
    if (fd < 0) {
        perror("Failed to open device");
        return -1;
    }

    // 获取DRM资源信息
    resources = drmModeGetResources(fd);
    if (!resources) {
        perror("Failed to get DRM resources");
        return -1;
    }

    // 查找第一个连接器
    for (int i = 0; i < resources->count_connectors; i++) {
        connector = drmModeGetConnector(fd, resources->connectors[i]);
        if (connector && connector->connection == DRM_MODE_CONNECTED) {
            connector_id = connector->connector_id;
            break;
        }
        drmModeFreeConnector(connector);
    }

    if (!connector) {
        perror("Failed to get connector");
        return -1;
    }

    // 获取连接器模式信息
    for (int i = 0; i < connector->count_modes; i++) {
        mode = connector->modes[i];
        if (mode.hdisplay == 1024 && mode.vdisplay == 768) {
            break;
        }
    }

    if (mode.hdisplay != 1024 || mode.vdisplay != 768) {
        perror("Failed to find valid mode");
        return -1;
    }

    // 查找支持该模式的编码器
    encoder_id = connector->encoder_id;
    encoder = drmModeGetEncoder(fd, encoder_id);
    if (!encoder) {
        perror("Failed to get encoder");
        return -1;
    }

    crtc_id = encoder->crtc_id;

    // 设置DRM客户端能力
    ioctl(fd, DRM_IOCTL_SET_CLIENT_CAP, &cap);

    // 创建Dumb Buffer
    memset(&create, 0, sizeof(create));
    create.width = mode.hdisplay;
    create.height = mode.vdisplay;
    create.bpp = 32;
    create.flags = 0;
    create.handle = 0;
    if (ioctl(fd, DRM_IOCTL_MODE_CREATE_DUMB, &create) < 0) {
        perror("Failed to create dumb buffer");
        return -1;
    }

    // 映射Dumb Buffer
    memset(&map, 0, sizeof(map));
    map.handle = create.handle;
    if (ioctl(fd, DRM_IOCTL_MODE_MAP_DUMB, &map) < 0) {
        perror("Failed to map dumb buffer");
        return -1;
    }

    // 将Dumb Buffer映射到FrameBuffer
    fb_fd = open(FB_DEVICE, O_RDWR);
    if (fb_fd < 0) {
        perror("Failed to open framebuffer device");
        return -1;
    }

    if (ioctl(fb_fd, FBIOGET_VSCREENINFO, &var_info) < 0) {
        perror("Failed to get variable screen info");
        return -1;
    }

    var_info.xres = mode.hdisplay;
    var_info.yres = mode.vdisplay;
    var_info.bits_per_pixel = 32;
    if (ioctl(fb_fd, FBIOPUT_VSCREENINFO, &var_info) < 0) {
        perror("Failed to put variable screen info");
        return -1;
    }

    fb_map = mmap(NULL, create.size, PROT_READ | PROT_WRITE, MAP_SHARED, fb_fd, 0);
    if (fb_map == MAP_FAILED) {
        perror("Failed to map framebuffer");
        return -1;
    }

    // 创建DRM FrameBuffer
    memset(&fcmd, 0, sizeof(fcmd));
    fcmd.width = create.width;
    fcmd.height = create.height;
    fcmd.pitch = create.pitch;
    fcmd.bpp = create.bpp;
    fcmd.handle = create.handle;
    if (ioctl(fd, DRM_IOCTL_MODE_ADDFB, &fcmd) < 0) {
        perror("Failed to create DRM framebuffer");
        return -1;
    }

    // 清空FrameBuffer
    buf = (uint32_t*)fb_map;
    memset(buf, 0, create.size);

    // 在FrameBuffer上绘制指定的图像
    // 这里使用了32位颜色格式，每个像素占用4个字节，依次是B,G,R,A
    for (int i = 0; i < mode.hdisplay; i++) {
        for (int j = 0; j < mode.vdisplay; j++) {
            uint32_t color = 0x000000FF; // 红色
            buf[i + j * mode.hdisplay] = color;
        }
    }

    // 设置CRTC模式
    drmModeSetCrtc(fd, crtc_id, fcmd.fb_id, 0, 0, &connector_id, 1, &mode);

    // 等待一段时间
    sleep(5);

    // 清理资源
    drmModeRmFB(fd, fcmd.fb_id);
    munmap(fb_map, create.size);
    close(fb_fd);
    drmModeFreeEncoder(encoder);
    drmModeFreeConnector(connector);
    drmModeFreeResources(resources);
    close(fd);
    return 0;
}

这个代码示例使用了DRM和FrameBuffer来显示指定的图像。在代码中，我们首先打开DRM设备，获取DRM资源信息，查找连接器和编码器，以及选择合适的显示模式。然后，我们创建Dumb Buffer、映射Dumb Buffer和将Dumb Buffer映射到FrameBuffer。接着，我们创建DRM FrameBuffer，并在FrameBuffer上绘制指定的图像。最后，我们设置CRTC模式，显示图像，并在5秒后清理资源。