linuxkpi: Add <linux/cgroup_dmem.h>

In this header, we declare empty stubs for all functions, as if
`CONFIG_CGROUP_DMEM` was disabled is Linux.

The DRM TTM memory manager started to use this in Linux 6.14.

Reviewed by:	emaste
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D57702

1 files changed, 58 insertions, 0 deletions

diff --git a/sys/compat/linuxkpi/common/include/linux/cgroup_dmem.h b/sys/compat/linuxkpi/common/include/linux/cgroup_dmem.h
new file mode 100644
index 000000000000..03c0600c1bee
--- /dev/null
+++ b/sys/compat/linuxkpi/common/include/linux/cgroup_dmem.h
@@ -0,0 +1,58 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2026 The FreeBSD Foundation
+ */
+
+#ifndef _LINUXKPI_LINUX_CGROUP_DMEM_H_
+#define	_LINUXKPI_LINUX_CGROUP_DMEM_H_
+
+#include <linux/types.h>
+#include <linux/llist.h>
+
+struct dmem_cgroup_pool_state;
+struct dmem_cgroup_region;
+
+static inline __printf(2,3) struct dmem_cgroup_region *
+dmem_cgroup_register_region(uint64_t size, const char *name_fmt, ...)
+{
+	return (NULL);
+}
+
+static inline void
+dmem_cgroup_unregister_region(struct dmem_cgroup_region *region)
+{
+}
+
+static inline int
+dmem_cgroup_try_charge(struct dmem_cgroup_region *region, u64 size,
+    struct dmem_cgroup_pool_state **ret_pool,
+    struct dmem_cgroup_pool_state **ret_limit_pool)
+{
+	*ret_pool = NULL;
+
+	if (ret_limit_pool)
+		*ret_limit_pool = NULL;
+
+	return (0);
+}
+
+static inline void
+dmem_cgroup_uncharge(struct dmem_cgroup_pool_state *pool, uint64_t size)
+{
+}
+
+static inline
+bool dmem_cgroup_state_evict_valuable(struct dmem_cgroup_pool_state *limit_pool,
+    struct dmem_cgroup_pool_state *test_pool,
+    bool ignore_low, bool *ret_hit_low)
+{
+	return (true);
+}
+
+static inline void
+dmem_cgroup_pool_state_put(struct dmem_cgroup_pool_state *pool)
+{
+}
+
+#endif /* _LINUXKPI_LINUX_CGROUP_DMEM_H_ */