掌機 - My Mini - C/C++ - DRM/KMS - Enum CRTC

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

main.c

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <xf86drm.h>
#include <xf86drmMode.h>
   
int main(int argc, char *argv[])
{
    int i = 0;
    int j = 0;
    int fd = -1;
    drmModeRes *res = NULL;
   
    fd = open("/dev/dri/card0", O_RDWR | O_CLOEXEC);
    res = drmModeGetResources(fd);
   
    for (i = 0; i < res->count_connectors; i++) {
        drmModeConnector *conn = drmModeGetConnector(fd, res->connectors[i]);
 
        if (conn) {
            if ((conn->connection == DRM_MODE_CONNECTED) && conn->count_modes) {
                printf("conn[%d].connector_id=%d\n", i, conn->connector_id);
                printf("conn[%d].encoder_id=%d\n", i, conn->encoder_id);
   
                for (j = 0; j < conn->count_modes; j++) {
                    drmModeModeInfo *mode = &conn->modes[j];
   
                    printf("conn[%d].mode[%d]=%s (%dx%dx%d)\n", i, j, mode->name, mode->hdisplay, mode->vdisplay, mode->vrefresh);
                }
            }
            drmModeFreeConnector(conn);
        }
    }
 
    for (i = 0; i < res->count_encoders; i++) {
        drmModeEncoder *enc = drmModeGetEncoder(fd, res->encoders[i]);
 
        if (enc) {
            printf("enc[%d].encoder_id=%d\n", i, enc->encoder_id);
            printf("enc[%d].crtc_id=%d\n", i, enc->crtc_id);
            drmModeFreeEncoder(enc);
        }
    }

    for (i = 0; i < res->count_crtcs; i++) {
        drmModeCrtc *crtc = drmModeGetCrtc(fd, res->crtcs[i]);

        if (crtc) {
            printf("crtc[%d].crtc_id=%d\n", i, crtc->crtc_id);
            printf("crtc[%d].buffer_id=%d\n", i, crtc->buffer_id);
            printf("crtc[%d].x=%d\n", i, crtc->x);
            printf("crtc[%d].y=%d\n", i, crtc->x);
            printf("crtc[%d].width=%d\n", i, crtc->width);
            printf("crtc[%d].height=%d\n", i, crtc->height);
            printf("crtc[%d].mode.name=%s\n", i, crtc->mode.name);
            drmModeFreeCrtc(crtc);
        }
    } 
    drmModeFreeResources(res);
    close(fd);
    return 0;
}

編譯、執行

$ /opt/flip/bin/aarch64-linux-gcc main.c -o main -I/opt/flip/aarch64-flip-linux-gnu/sysroot/usr/include/libdrm -ldrm

RuiSuo:~/roms # kill -STOP `pidof emulationstation`
RuiSuo:~/roms # ./main
    conn[0].connector_id=95
    conn[0].encoder_id=94
    conn[0].mode[0]=640x480 (640x480x59)
    enc[0].encoder_id=94
    enc[0].crtc_id=69
    crtc[0].crtc_id=69
    crtc[0].buffer_id=0
    crtc[0].x=0
    crtc[0].y=0
    crtc[0].width=640
    crtc[0].height=480
    crtc[0].mode.name=640x480