/*
 * DF-4439 probe: is the DRM atomic ioctl surface present on this guest?
 *
 * The finding (missing backport of Linux 4e076c73e4f6: drm_atomic_state holds
 * no drm_device reference while nonblocking commits outlive the ioctl on
 * system_unbound_wq) can only be exercised where a DRM driver is attached.
 * This probe documents availability: it looks for the DRM device nodes,
 * opens one if present, queries DRM_IOCTL_VERSION and
 * DRM_IOCTL_MODE_GETRESOURCES (atomic-capable stack), and reports what it
 * found.  On the audit guest (QEMU std VGA, no i915/amdgpu/radeon) there is
 * no DRM device, so the race cannot be driven here.
 *
 * Build: cc -O -o probe_drm probe_drm.c
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/types.h>

/* Minimal local copies of the drm uapi pieces (avoid include-path issues) */
struct drm_version_ {
	int version_major, version_minor, version_patchlevel;
	size_t name_len;  char *name;
	size_t date_len;  char *date;
	size_t desc_len;  char *desc;
};
#define DRM_IOCTL_VERSION_ _IOWR(0x00, 0x02, struct drm_version_)

#define DRM_IOCTL_BASE	'd'
#define DRM_IOCTL_MODE_GETRESOURCES_ _IOWR(DRM_IOCTL_BASE, 0xA0, int[8])

int main(void)
{
	static const char *candidates[] = {
		"/dev/drm0", "/dev/drm1", "/dev/dri/card0", "/dev/dri/card1",
		"/dev/dri/renderD128", NULL
	};
	int i, fd = -1;

	for (i = 0; candidates[i]; i++) {
		fd = open(candidates[i], O_RDWR);
		if (fd >= 0) {
			printf("opened %s\n", candidates[i]);
			break;
		}
		printf("%s: %s\n", candidates[i], strerror(errno));
	}
	if (fd < 0) {
		printf("RESULT: no DRM device node available on this system\n");
		printf("RESULT: DF-4439 race (nonblocking atomic commit vs driver\n");
		printf("RESULT: unload) is NOT exercisable on this guest\n");
		return 1;
	}

	struct drm_version_ v;
	char name[64] = {0};
	memset(&v, 0, sizeof(v));
	v.name = name; v.name_len = sizeof(name);
	if (ioctl(fd, DRM_IOCTL_VERSION_, &v) == 0)
		printf("DRM version: %d.%d driver=%s\n",
		       v.version_major, v.version_minor, name);
	else
		printf("DRM_IOCTL_VERSION: %s\n", strerror(errno));

	int res[8] = {0};
	if (ioctl(fd, DRM_IOCTL_MODE_GETRESOURCES_, res) == 0)
		printf("KMS present: crtcs=%d connectors=%d fb=%d\n",
		       res[0], res[2], res[4]);
	else
		printf("DRM_IOCTL_MODE_GETRESOURCES: %s\n", strerror(errno));

	printf("RESULT: DRM present; DF-4439 race harness would run here\n");
	close(fd);
	return 0;
}