/*
 * drm_sg_probe.c -- DF-5193 guest probe (run as root)
 *
 * Attempts to reach drm_legacy_sg_alloc / drm_legacy_sg_free via
 * DRM_IOCTL_SG_ALLOC on any DRM device node present.
 *
 * Expected on this guest (QEMU std-VGA, no GPU): no /dev/dri/* and no
 * /dev/drm/* nodes exist -> open() fails ENOENT -> the scatter-gather
 * path has no runtime surface here.
 *
 * Even on a DRM-equipped system the path is double-gated:
 *   - drm_ioctl.c:636-637: DRM_AUTH|DRM_MASTER|DRM_ROOT_ONLY
 *     (capable(CAP_SYS_ADMIN) -> caps_priv_check_self, drm_ioctl.c:538)
 *   - no in-tree driver sets DRIVER_SG(0x10)|DRIVER_LEGACY(0x2)
 *     (i915_drv.c:3284, radeon_drv.c:671) so drm_scatter.c:69-73/125-129
 *     returns -EOPNOTSUPP even for root.
 */
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>

int main(void)
{
	static const char *nodes[] = {
		"/dev/dri/card0", "/dev/dri/renderD128",
		"/dev/drm/0", "/dev/dri0", NULL
	};
	int i, fd;

	for (i = 0; nodes[i]; i++) {
		errno = 0;
		fd = open(nodes[i], O_RDWR);
		printf("open(%s) -> fd=%d errno=%d (%s)\n", nodes[i], fd,
		    errno, fd < 0 ? strerror(errno) : "opened");
		if (fd >= 0)
			close(fd);
	}
	printf("[*] kldstat modules and /boot/kernel contents carry the "
	       "authoritative answer: which drm drivers exist at all.\n");
	return 0;
}