From 321c78384ee14fa8641d6ee0d556dd4286b69b7c Mon Sep 17 00:00:00 2001
From: jsg <jsg@openbsd.org>
Date: Tue, 7 Apr 2026 09:11:15 +0000
Subject: [PATCH] add idr_alloc_cyclic() for 6.18.21 drm

---
 sys/dev/pci/drm/drm_linux.c         | 41 ++++++++++++++++++++++++++++-
 sys/dev/pci/drm/include/linux/idr.h |  5 +++-
 2 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/sys/dev/pci/drm/drm_linux.c b/sys/dev/pci/drm/drm_linux.c
index 2cad5cf4f0b..a96342d2f4a 100644
--- a/sys/dev/pci/drm/drm_linux.c
+++ b/sys/dev/pci/drm/drm_linux.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: drm_linux.c,v 1.134 2026/03/31 08:54:14 jsg Exp $	*/
+/*	$OpenBSD: drm_linux.c,v 1.135 2026/04/07 09:11:15 jsg Exp $	*/
 /*
  * Copyright (c) 2013 Jonathan Gray <jsg@openbsd.org>
  * Copyright (c) 2015, 2016 Mark Kettenis <kettenis@openbsd.org>
@@ -810,6 +810,7 @@ void
 idr_init(struct idr *idr)
 {
 	SPLAY_INIT(&idr->tree);
+	idr->next = 0;
 }
 
 void
@@ -867,6 +868,44 @@ idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
 	return id->id;
 }
 
+/* [start, end) */
+int
+idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
+{
+	int flags = (gfp_mask & GFP_NOWAIT) ? PR_NOWAIT : PR_WAITOK;
+	struct idr_entry *id;
+
+	KERNEL_ASSERT_LOCKED();
+
+	if (idr_entry_cache) {
+		id = idr_entry_cache;
+		idr_entry_cache = NULL;
+	} else {
+		id = pool_get(&idr_pool, flags);
+		if (id == NULL)
+			return -ENOMEM;
+	}
+
+	if (end <= 0)
+		end = INT_MAX;
+
+	id->id = idr->next;
+	while (SPLAY_INSERT(idr_tree, &idr->tree, id)) {
+		id->id++;
+		if (id->id == end) {
+			id->id = start;
+		} else if (id->id == idr->next) {
+			pool_put(&idr_pool, id);
+			return -ENOSPC;
+		}
+	}
+	id->ptr = ptr;
+	idr->next = id->id + 1;
+	if (idr->next == end)
+		idr->next = start;
+	return id->id;
+}
+
 void *
 idr_replace(struct idr *idr, void *ptr, unsigned long id)
 {
diff --git a/sys/dev/pci/drm/include/linux/idr.h b/sys/dev/pci/drm/include/linux/idr.h
index 169f326dc25..c39f568282f 100644
--- a/sys/dev/pci/drm/include/linux/idr.h
+++ b/sys/dev/pci/drm/include/linux/idr.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: idr.h,v 1.9 2026/04/07 09:04:16 jsg Exp $	*/
+/*	$OpenBSD: idr.h,v 1.10 2026/04/07 09:11:15 jsg Exp $	*/
 /*
  * Copyright (c) 2016 Mark Kettenis
  *
@@ -31,16 +31,19 @@ struct idr_entry {
 
 struct idr {
 	SPLAY_HEAD(idr_tree, idr_entry) tree;
+	unsigned long next;
 };
 
 #define DEFINE_IDR(name)					\
 	struct idr name = {					\
 		.tree = SPLAY_INITIALIZER(&name.idr.tree),	\
+		.next = 0					\
 	}
 
 void idr_init(struct idr *);
 void idr_preload(unsigned int);
 int idr_alloc(struct idr *, void *, int, int, gfp_t);
+int idr_alloc_cyclic(struct idr *, void *, int, int, gfp_t);
 void *idr_find(struct idr *, unsigned long);
 void *idr_replace(struct idr *, void *, unsigned long);
 void *idr_remove(struct idr *, unsigned long);