render/allocator: use empty DRM lease to re-open node
This allows us to obtain a new DRM file description without relying
on filesystem permissions.
#include <unistd.h>
#include <wlr/util/log.h>
#include <xf86drm.h>
+#include <xf86drmMode.h>
#include "backend/backend.h"
#include "render/allocator/allocator.h"
#include "render/allocator/drm_dumb.h"
@@ -22,10 +23,22 @@ void wlr_allocator_init(struct wlr_allocator *alloc,
/* Re-open the DRM node to avoid GEM handle ref'counting issues. See:
* https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/110
- * TODO: don't assume we have the permission to just open the DRM node,
- * find another way to re-open it.
*/
static int reopen_drm_node(int drm_fd, bool allow_render_node) {
+ if (drmIsMaster(drm_fd)) {
+ // Only recent kernels support empty leases
+ uint32_t lessee_id;
+ int lease_fd = drmModeCreateLease(drm_fd, NULL, 0, 0, &lessee_id);
+ if (lease_fd >= 0) {
+ return lease_fd;
+ } else if (lease_fd != -EINVAL && lease_fd != -EOPNOTSUPP) {
+ wlr_log_errno(WLR_ERROR, "drmModeCreateLease failed");
+ return -1;
+ }
+ wlr_log(WLR_DEBUG, "drmModeCreateLease failed, "
+ "falling back to plain open");
+ }
+
char *name = NULL;
if (allow_render_node) {
name = drmGetRenderDeviceNameFromFd(drm_fd);
