cgroup/dmem: Introduce struct dmem_cgroup_init for region initialization

Replace the bare u64 size argument to dmem_cgroup_register_region() and
drmm_cgroup_register_region() with a const struct dmem_cgroup_init *
pointer. The struct currently carries only the size field, but using a
struct makes the API extensible: future callers can supply additional
initialization parameters without adding more positional arguments.

Update all in-tree callers (amdgpu, xe) to use a compound-literal
initializer.

v5:
- Commit introduced.

Assisted-by: GitHub_Copilot:claude-sonnet-4.6
Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Tested-by: Thadeu Lima de Souza Cascardo <cascardo@igalia.com>
Link: https://patch.msgid.link/20260725100036.2372-3-thomas.hellstrom@linux.intel.com
Acked-by: Dave Airlie <airlied@redhat.com>
Acked-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>

drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c

@@ -23,6 +23,7 @@
  */
 
 #include <linux/dma-mapping.h>
+#include <linux/cgroup_dmem.h>
 #include <drm/ttm/ttm_range_manager.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_buddy.h>
@@ -932,7 +933,10 @@ int amdgpu_vram_mgr_init(struct amdgpu_device *adev)
 	if (err)
 		return err;
 
-	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram", adev->gmc.real_vram_size);
+	man->cg = drmm_cgroup_register_region(adev_to_drm(adev), "vram",
+					      &(struct dmem_cgroup_init){
+						.size = adev->gmc.real_vram_size,
+					      });
 	if (IS_ERR(man->cg))
 		return PTR_ERR(man->cg);
 

drivers/gpu/drm/drm_drv.c

@@ -960,17 +960,19 @@ static void drmm_cg_unregister_region(struct drm_device *dev, void *arg)
  * drmm_cgroup_register_region - Register a region of a DRM device to cgroups
  * @dev: device for region
  * @region_name: Region name for registering
- * @size: Size of region in bytes
+ * @init: Initialization parameters for the region.
  *
  * This decreases the ref-count of @dev by one. The device is destroyed if the
  * ref-count drops to zero.
  */
-struct dmem_cgroup_region *drmm_cgroup_register_region(struct drm_device *dev, const char *region_name, u64 size)
+struct dmem_cgroup_region *
+drmm_cgroup_register_region(struct drm_device *dev, const char *region_name,
+			    const struct dmem_cgroup_init *init)
 {
 	struct dmem_cgroup_region *region;
 	int ret;
 
-	region = dmem_cgroup_register_region(size, "drm/%s/%s", dev->unique, region_name);
+	region = dmem_cgroup_register_region(init, "drm/%s/%s", dev->unique, region_name);
 	if (IS_ERR_OR_NULL(region))
 		return region;
 

drivers/gpu/drm/nouveau/nouveau_ttm.c

@@ -23,6 +23,7 @@
  * USE OR OTHER DEALINGS IN THE SOFTWARE.
  */
 
+#include <linux/cgroup_dmem.h>
 #include <linux/limits.h>
 
 #include <drm/ttm/ttm_range_manager.h>
@@ -189,7 +190,9 @@ nouveau_ttm_init_vram(struct nouveau_drm *drm)
 		man->func = &nouveau_vram_manager;
 
 		man->cg = drmm_cgroup_register_region(drm->dev, "vram",
-						      drm->gem.vram_available);
+						      &(struct dmem_cgroup_init){
+							      .size = drm->gem.vram_available
+						      });
 		if (IS_ERR(man->cg))
 			return PTR_ERR(man->cg);
 

drivers/gpu/drm/xe/xe_ttm_vram_mgr.c

@@ -4,6 +4,8 @@
  * Copyright (C) 2021-2022 Red Hat
  */
 
+#include <linux/cgroup_dmem.h>
+
 #include <drm/drm_managed.h>
 #include <drm/drm_drv.h>
 #include <drm/drm_buddy.h>
@@ -303,7 +305,10 @@ int __xe_ttm_vram_mgr_init(struct xe_device *xe, struct xe_ttm_vram_mgr *mgr,
 	int err;
 
 	name = mem_type == XE_PL_VRAM0 ? "vram0" : "vram1";
-	man->cg = drmm_cgroup_register_region(&xe->drm, name, size);
+	man->cg = drmm_cgroup_register_region(&xe->drm, name,
+					      &(struct dmem_cgroup_init){
+						.size = size,
+					      });
 	if (IS_ERR(man->cg))
 		return PTR_ERR(man->cg);
 

include/drm/drm_drv.h

@@ -34,6 +34,7 @@
 
 #include <drm/drm_device.h>
 
+struct dmem_cgroup_init;
 struct dmem_cgroup_region;
 struct drm_fb_helper;
 struct drm_fb_helper_surface_size;
@@ -433,7 +434,8 @@ void *__devm_drm_dev_alloc(struct device *parent,
 
 struct dmem_cgroup_region *
 drmm_cgroup_register_region(struct drm_device *dev,
-			    const char *region_name, u64 size);
+			    const char *region_name,
+			    const struct dmem_cgroup_init *init);
 
 /**
  * devm_drm_dev_alloc - Resource managed allocation of a &drm_device instance

include/linux/cgroup_dmem.h

@@ -14,8 +14,18 @@ struct dmem_cgroup_pool_state;
 /* Opaque definition of a cgroup region, used internally */
 struct dmem_cgroup_region;
 
+/**
+ * struct dmem_cgroup_init - Initialization parameters for a dmem cgroup region.
+ * @size: Size of the region in bytes.
+ */
+struct dmem_cgroup_init {
+	u64 size;
+};
+
 #if IS_ENABLED(CONFIG_CGROUP_DMEM)
-struct dmem_cgroup_region *dmem_cgroup_register_region(u64 size, const char *name_fmt, ...) __printf(2,3);
+struct dmem_cgroup_region *
+dmem_cgroup_register_region(const struct dmem_cgroup_init *init,
+			    const char *name_fmt, ...) __printf(2, 3);
 void dmem_cgroup_unregister_region(struct dmem_cgroup_region *region);
 int dmem_cgroup_try_charge(struct dmem_cgroup_region *region, u64 size,
 			   struct dmem_cgroup_pool_state **ret_pool,
@@ -33,8 +43,8 @@ struct dmem_cgroup_pool_state *dmem_cgroup_get_common_ancestor(struct dmem_cgrou
 
 void dmem_cgroup_pool_state_put(struct dmem_cgroup_pool_state *pool);
 #else
-static inline __printf(2,3) struct dmem_cgroup_region *
-dmem_cgroup_register_region(u64 size, const char *name_fmt, ...)
+static inline __printf(2, 3) struct dmem_cgroup_region *
+dmem_cgroup_register_region(const struct dmem_cgroup_init *init, const char *name_fmt, ...)
 {
 	return NULL;
 }

kernel/cgroup/dmem.c

@@ -502,7 +502,7 @@ EXPORT_SYMBOL_GPL(dmem_cgroup_unregister_region);
 
 /**
  * dmem_cgroup_register_region() - Register a regions for dev cgroup.
- * @size: Size of region to register, in bytes.
+ * @init: Initialization parameters for the region.
  * @fmt: Region parameters to register
  *
  * This function registers a node in the dmem cgroup with the
@@ -511,13 +511,15 @@ EXPORT_SYMBOL_GPL(dmem_cgroup_unregister_region);
  *
  * Return: NULL or a struct on success, PTR_ERR on failure.
  */
-struct dmem_cgroup_region *dmem_cgroup_register_region(u64 size, const char *fmt, ...)
+struct dmem_cgroup_region *
+dmem_cgroup_register_region(const struct dmem_cgroup_init *init,
+			    const char *fmt, ...)
 {
 	struct dmem_cgroup_region *ret;
 	char *region_name;
 	va_list ap;
 
-	if (!size)
+	if (!init || !init->size)
 		return NULL;
 
 	va_start(ap, fmt);
@@ -534,7 +536,7 @@ struct dmem_cgroup_region *dmem_cgroup_register_region(u64 size, const char *fmt
 
 	INIT_LIST_HEAD(&ret->pools);
 	ret->name = region_name;
-	ret->size = size;
+	ret->size = init->size;
 	kref_init(&ret->ref);
 
 	spin_lock(&dmemcg_lock);