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From:   Jim Shargo <jshargo@chromium.org>
To:     jshargo@google.com,
        Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
        Melissa Wen <melissa.srw@gmail.com>,
        Haneen Mohammed <hamohammed.sa@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        David Airlie <airlied@linux.ie>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Jonathan Corbet <corbet@lwn.net>
Cc:     Jim Shargo <jshargo@chromium.org>, dri-devel@lists.freedesktop.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 4/5] drm/vkms: Add ConfigFS scaffolding to VKMS
Date:   Fri, 22 Jul 2022 17:32:12 -0400
Message-Id: <20220722213214.1377835-5-jshargo@chromium.org>
In-Reply-To: <20220722213214.1377835-1-jshargo@chromium.org>
References: <20220722213214.1377835-1-jshargo@chromium.org>
MIME-Version: 1.0
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Precedence: bulk

This change adds the basic scaffolding for ConfigFS, including setting
up the default directories. It does not allow for the registration of
configfs-backed devices, which is complex and provided in a follow-up
commit.

This CL includes docs about using ConfigFS with VKMS, but I'll summarize
in brief here as well (assuming ConfigFS is mounted at /config/):

To create a new configuration, you can do so via `mkdir
/config/vkms/my-device`.

This will create a number of directories and files automatically:

	/config
	`-- vkms
	    `-- my-device
		|-- connectors
		|-- crtcs
		|-- encoders
		|-- planes
		`-- is_registered

You can then configure objects by mkdir'ing in each of the directories.

When you're satisfied, you can `echo 1 > /config/vkms/my-device/is_registered`.
This will create a new device according to your configuration.

For now, this will fail, but the next change will add support for it.

Signed-off-by: Jim Shargo <jshargo@chromium.org>
---
 Documentation/gpu/vkms.rst           |  76 ++++
 drivers/gpu/drm/Kconfig              |   1 +
 drivers/gpu/drm/vkms/Makefile        |   1 +
 drivers/gpu/drm/vkms/vkms_configfs.c | 527 +++++++++++++++++++++++++++
 drivers/gpu/drm/vkms/vkms_drv.c      |  28 +-
 drivers/gpu/drm/vkms/vkms_drv.h      |  75 +++-
 drivers/gpu/drm/vkms/vkms_output.c   |  11 +-
 7 files changed, 711 insertions(+), 8 deletions(-)
 create mode 100644 drivers/gpu/drm/vkms/vkms_configfs.c

diff --git a/Documentation/gpu/vkms.rst b/Documentation/gpu/vkms.rst
index 9c873c3912cc..f5f8ea0de5bc 100644
--- a/Documentation/gpu/vkms.rst
+++ b/Documentation/gpu/vkms.rst
@@ -51,6 +51,82 @@ To disable the driver, use ::
 
   sudo modprobe -r vkms
 
+Configuration With ConfigFS
+===========================
+
+VKMS is instrumented with support for configuration via `ConfigFS`. With VKMS
+installed, you can mount ConfigFS at /config/ like so::
+
+  mkdir -p /config/
+  sudo mount -t configfs none /config
+
+This allows you to configure multiple virtual cards in addition to an immutable
+"default" card created by the driver at initialization time.
+
+To set up a new card, create a new directory under the vkms configfs 
+directory::
+
+  $ mkdir /config/vkms/test
+
+With your card created you'll find an new directory ready to be configured::
+
+  /config
+  `-- vkms
+      |-- default
+      |   `-- is_registered
+      `-- test
+          |-- connectors
+          |-- crtcs
+          |-- encoders
+          |-- planes
+          `-- is_registered
+
+Each directory you add within the connectors, crtcs, encoders, and planes
+directories will let you configure a new object of that type. Adding new
+objects will automatically create a set of default files and folders you can
+use to configure that object.
+
+For instance, we can set up a very basic driver like so::
+
+  DRM_PLANE_TYPE_PRIMARY=1
+  DRM_PLANE_TYPE_CURSOR=2
+  DRM_PLANE_TYPE_OVERLAY=0
+
+  mkdir /config/vkms/test/planes/primary
+  echo $DRM_PLANE_TYPE_PRIMARY > /config/vkms/test/planes/primary/type
+
+  mkdir /config/vkms/test/planes/other_primary
+  echo $DRM_PLANE_TYPE_PRIMARY > /config/vkms/test/planes/other_primary/type
+
+  mkdir /config/vkms/test/planes/cursor
+  echo $DRM_PLANE_TYPE_CURSOR > /config/vkms/test/planes/cursor/type
+
+  mkdir /config/vkms/test/planes/overlay
+  echo $DRM_PLANE_TYPE_OVERLAY > /config/vkms/test/planes/overlay/type
+
+  mkdir /config/vkms/test/crtcs/crtc
+  mkdir /config/vkms/test/crtcs/crtc_other
+  mkdir /config/vkms/test/encoders/encoder
+  mkdir /config/vkms/test/connectors/connector
+
+  ln -s /config/vkms/test/encoders/encoder /config/vkms/test/connectors/connector/possible_encoders
+  ln -s /config/vkms/test/crtcs/crtc /config/vkms/test/encoders/encoder/possible_crtcs/
+  ln -s /config/vkms/test/crtcs/crtc /config/vkms/test/planes/primary/possible_crtcs/
+  ln -s /config/vkms/test/crtcs/crtc /config/vkms/test/planes/cursor/possible_crtcs/
+  ln -s /config/vkms/test/crtcs/crtc /config/vkms/test/planes/overlay/possible_crtcs/
+  ln -s /config/vkms/test/crtcs/crtc_other /config/vkms/test/planes/overlay/possible_crtcs/
+
+You can see that specific attributes, such as `.../<plane>/type`, can be
+configured by writing into them. Associating objects together can be done via
+symlinks.
+
+Finally, to register your newly configured objects with DRM so you can use your
+virtual device, all you need to do is write `1` into the special file 
+`/config/vkms/test/is_registered``, which will return non-zero on error.
+
+When you're done with the virtual card, all you need to do is `rmdir` the root
+directory.
+
 Testing With IGT
 ================
 
diff --git a/drivers/gpu/drm/Kconfig b/drivers/gpu/drm/Kconfig
index f1422bee3dcc..5c90c82fab6d 100644
--- a/drivers/gpu/drm/Kconfig
+++ b/drivers/gpu/drm/Kconfig
@@ -307,6 +307,7 @@ config DRM_VKMS
 	depends on DRM && MMU
 	select DRM_KMS_HELPER
 	select DRM_GEM_SHMEM_HELPER
+	select CONFIGFS_FS
 	select CRC32
 	default n
 	help
diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
index 72f779cbfedd..3efb7b0f5319 100644
--- a/drivers/gpu/drm/vkms/Makefile
+++ b/drivers/gpu/drm/vkms/Makefile
@@ -3,6 +3,7 @@ vkms-y := \
 	vkms_drv.o \
 	vkms_plane.o \
 	vkms_output.o \
+	vkms_configfs.o \
 	vkms_crtc.o \
 	vkms_composer.o \
 	vkms_writeback.o
diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
new file mode 100644
index 000000000000..fa0d8700258e
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -0,0 +1,527 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/configfs.h>
+#include <linux/kernel.h>
+#include <linux/mutex.h>
+
+#include <drm/drm_plane.h>
+#include <drm/drm_print.h>
+
+#include "vkms_drv.h"
+
+/**
+ * DOC: ConfigFS Support for VKMS
+ *
+ * When ConfigFS is mounted, say at /config/, we add a /config/vkms/
+ * directory. Each folder in this directory represents a different
+ * virtual driver. Drivers can be "registered", meaning that they're
+ * available to use as a DRM driver. Initially, this just contains a
+ * registered "default" device.
+ *
+ * Users can mkdir in this the VKMS directory to begin the process of
+ * configuring a new device. Users can mkdir in the automatically
+ * created "connectors", "crtcs", "encoders", and "planes" folders to
+ * set up those objects.
+ *
+ * In order to create associations between objects, users can symlink
+ * the object's directory. For instance, to make a plane work with a
+ * CRTC, the user will add a symlink like so:
+ * /config/vkms/card/planes/<plane>/possible_crtcs/<crtc_symlink>
+ *
+ * Objects may have files (in ConfigFS-speak, attributes) that allow
+ * for additional configuration. For instance, a user can set the
+ * plane type by writing the appropriate value to the "type" property
+ * in the plane's directory.
+ *
+ * Once the driver is configured, the user can write a "1" to the
+ * "is_registered" file/attribute in the driver's directory. Until a
+ * virtual driver is registered, nothing DRM-related is set up.
+ */
+
+static struct config_item_type card_group_type;
+static struct config_item_type connectors_group_type;
+static struct config_item_type crtcs_group_type;
+static struct config_item_type encoders_group_type;
+static struct config_item_type planes_group_type;
+
+static void vkms_configfs_setup_default_groups(struct vkms_configfs *configfs,
+					       const char *name)
+{
+	config_group_init_type_name(&configfs->card_group, name,
+				    &card_group_type);
+
+	config_group_init_type_name(&configfs->connectors_group, "connectors",
+				    &connectors_group_type);
+	configfs_add_default_group(&configfs->connectors_group,
+				   &configfs->card_group);
+
+	config_group_init_type_name(&configfs->crtcs_group, "crtcs",
+				    &crtcs_group_type);
+	configfs_add_default_group(&configfs->crtcs_group,
+				   &configfs->card_group);
+
+	config_group_init_type_name(&configfs->encoders_group, "encoders",
+				    &encoders_group_type);
+	configfs_add_default_group(&configfs->encoders_group,
+				   &configfs->card_group);
+
+	config_group_init_type_name(&configfs->planes_group, "planes",
+				    &planes_group_type);
+	configfs_add_default_group(&configfs->planes_group,
+				   &configfs->card_group);
+}
+
+/* Root directory group and subsystem, e.g. /config/vkms/ */
+
+static struct config_group *make_root_group(struct config_group *group,
+					    const char *name)
+{
+	struct vkms_configfs *configfs =
+		kzalloc(sizeof(struct vkms_configfs), GFP_KERNEL);
+
+	if (!configfs)
+		return ERR_PTR(ENOMEM);
+
+	vkms_configfs_setup_default_groups(configfs, name);
+
+	return &configfs->card_group;
+}
+
+static void drop_root_group(struct config_group *group,
+			    struct config_item *item)
+{
+	struct vkms_configfs *configfs = item_to_configfs(item);
+
+	if (configfs->card)
+		vkms_card_destroy(configfs->card);
+
+	kfree(configfs);
+}
+
+static struct configfs_group_operations root_group_ops = {
+	.make_group = &make_root_group,
+	.drop_item = &drop_root_group,
+};
+
+static struct config_item_type vkms_type = {
+	.ct_group_ops = &root_group_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+static struct configfs_subsystem vkms_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_name = "vkms",
+			.ci_type = &vkms_type,
+		},
+	},
+};
+
+int vkms_init_configfs(void)
+{
+	config_group_init(&vkms_subsys.su_group);
+	mutex_init(&vkms_subsys.su_mutex);
+	return configfs_register_subsystem(&vkms_subsys);
+}
+
+void vkms_unregister_configfs(void)
+{
+	configfs_unregister_subsystem(&vkms_subsys);
+}
+
+/*
+ * Common helpers (common sub-groups)
+ */
+
+/* Possible CRTCs, e.g. /config/vkms/card/<object>/possible_crtcs/<symlink> */
+
+static struct config_item_type crtc_type;
+
+static int possible_crtcs_allow_link(struct config_item *src,
+				     struct config_item *target)
+{
+	struct vkms_config_links *links = item_to_config_links(src);
+	struct vkms_config_crtc *crtc;
+
+	if (target->ci_type != &crtc_type) {
+		DRM_ERROR("Unable to link non-CRTCs.");
+		return -EINVAL;
+	}
+
+	crtc = item_to_config_crtc(target);
+
+	if (links->linked_object_bitmap & (1 << crtc->crtc_config_idx)) {
+		DRM_ERROR(
+			"Tried to add two symlinks to the same CRTC from the same object");
+		return -EINVAL;
+	}
+
+	links->linked_object_bitmap |= 1 << crtc->crtc_config_idx;
+
+	return 0;
+}
+
+static void possible_crtcs_drop_link(struct config_item *src,
+				     struct config_item *target)
+{
+	struct vkms_config_links *links = item_to_config_links(src);
+	struct vkms_config_crtc *crtc = item_to_config_crtc(target);
+
+	links->linked_object_bitmap &= ~(1 << crtc->crtc_config_idx);
+}
+
+static struct configfs_item_operations possible_crtcs_item_ops = {
+	.allow_link = &possible_crtcs_allow_link,
+	.drop_link = &possible_crtcs_drop_link,
+};
+
+static struct config_item_type possible_crtcs_group_type = {
+	.ct_item_ops = &possible_crtcs_item_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+static void add_possible_crtcs(struct config_group *parent,
+			       struct config_group *possible_crtcs)
+{
+	config_group_init_type_name(possible_crtcs, "possible_crtcs",
+				    &possible_crtcs_group_type);
+	configfs_add_default_group(possible_crtcs, parent);
+}
+
+/* Possible encoders, e.g. /config/vkms/card/connector/possible_encoders/<symlink> */
+
+static struct config_item_type encoder_type;
+
+static int possible_encoders_allow_link(struct config_item *src,
+					struct config_item *target)
+{
+	struct vkms_config_links *links = item_to_config_links(src);
+	struct vkms_config_encoder *encoder;
+
+	if (target->ci_type != &encoder_type) {
+		DRM_ERROR("Unable to link non-encoders.");
+		return -EINVAL;
+	}
+
+	encoder = item_to_config_encoder(target);
+
+	if (links->linked_object_bitmap & (1 << encoder->encoder_config_idx)) {
+		DRM_ERROR(
+			"Tried to add two symlinks to the same encoder from the same object");
+		return -EINVAL;
+	}
+
+	links->linked_object_bitmap |= 1 << encoder->encoder_config_idx;
+
+	return 0;
+}
+
+static void possible_encoders_drop_link(struct config_item *src,
+					struct config_item *target)
+{
+	struct vkms_config_links *links = item_to_config_links(src);
+	struct vkms_config_encoder *encoder = item_to_config_encoder(target);
+
+	links->linked_object_bitmap &= ~(1 << encoder->encoder_config_idx);
+}
+
+static struct configfs_item_operations possible_encoders_item_ops = {
+	.allow_link = &possible_encoders_allow_link,
+	.drop_link = &possible_encoders_drop_link,
+};
+
+static struct config_item_type possible_encoders_group_type = {
+	.ct_item_ops = &possible_encoders_item_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+static void add_possible_encoders(struct config_group *parent,
+				  struct config_group *possible_encoders)
+{
+	config_group_init_type_name(possible_encoders, "possible_encoders",
+				    &possible_encoders_group_type);
+	configfs_add_default_group(possible_encoders, parent);
+}
+
+/*
+ * Individual objects (connectors, crtcs, encoders, planes):
+ */
+
+/*  Connector item, e.g. /config/vkms/card/connectors/ID */
+
+static struct config_item_type connector_type = {
+	.ct_owner = THIS_MODULE,
+};
+
+/*  Crtc item, e.g. /config/vkms/card/crtcs/ID */
+
+static int crtc_allow_link(struct config_item *src, struct config_item *target)
+{
+	// TODO delete?
+	return 0;
+}
+
+static struct configfs_item_operations crtc_item_ops = {
+	.allow_link = &crtc_allow_link,
+};
+
+static struct config_item_type crtc_type = {
+	.ct_item_ops = &crtc_item_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+/*  Encoder item, e.g. /config/vkms/card/encoder/ID */
+
+static struct config_item_type encoder_type = {
+	.ct_owner = THIS_MODULE,
+};
+
+/*  Plane item, e.g. /config/vkms/card/planes/ID */
+
+static ssize_t plane_type_show(struct config_item *item, char *buf)
+{
+	struct vkms_config_plane *plane = item_to_config_plane(item);
+	return sprintf(buf, "%u", plane->type);
+}
+
+static ssize_t plane_type_store(struct config_item *item, const char *buf,
+				size_t len)
+{
+	struct vkms_config_plane *plane = item_to_config_plane(item);
+	int val, ret;
+
+	ret = kstrtouint(buf, 10, &val);
+	if (ret) {
+		return -ret;
+	}
+
+	if (val != DRM_PLANE_TYPE_PRIMARY && val != DRM_PLANE_TYPE_CURSOR &&
+	    val != DRM_PLANE_TYPE_OVERLAY) {
+		return -EINVAL;
+	}
+
+	plane->type = val;
+
+	return len;
+}
+
+CONFIGFS_ATTR(plane_, type);
+
+static struct configfs_attribute *plane_attrs[] = {
+	&plane_attr_type,
+	NULL,
+};
+
+static struct config_item_type plane_type = {
+	.ct_attrs = plane_attrs,
+	.ct_owner = THIS_MODULE,
+};
+
+/*
+ * Directory groups, e.g. /config/vkms/card/{planes, crtcs, ...}
+ */
+
+/* Connectors group: /config/vkms/card/connectors/ */
+
+static struct config_group *connectors_group_make(struct config_group *group,
+						  const char *name)
+{
+	struct vkms_config_connector *connector =
+		kzalloc(sizeof(struct vkms_config_connector), GFP_KERNEL);
+	if (!connector)
+		return ERR_PTR(ENOMEM);
+
+	config_group_init_type_name(&connector->config_group, name,
+				    &connector_type);
+	add_possible_encoders(&connector->config_group,
+			      &connector->possible_encoders.group);
+
+	return &connector->config_group;
+}
+
+static void connectors_group_drop(struct config_group *group,
+				  struct config_item *item)
+{
+	struct vkms_config_connector *connector =
+		item_to_config_connector(item);
+	kfree(connector);
+}
+
+static struct configfs_group_operations connectors_group_ops = {
+	.make_group = &connectors_group_make,
+	.drop_item = &connectors_group_drop,
+};
+
+static struct config_item_type connectors_group_type = {
+	.ct_group_ops = &connectors_group_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+/* CRTCs group: /config/vkms/card/crtcs/ */
+
+static struct config_group *crtcs_group_make(struct config_group *group,
+					     const char *name)
+{
+	struct vkms_configfs *configfs =
+		container_of(group, struct vkms_configfs, crtcs_group);
+	unsigned long next_idx = find_first_zero_bit(&configfs->allocated_crtcs,
+						     VKMS_MAX_OUTPUT_OBJECTS);
+	struct vkms_config_crtc *crtc;
+
+	if (next_idx == VKMS_MAX_OUTPUT_OBJECTS) {
+		DRM_ERROR("Unable to allocate another CRTC.");
+		return ERR_PTR(ENOMEM);
+	}
+
+	crtc = kzalloc(sizeof(struct vkms_config_crtc), GFP_KERNEL);
+	if (!crtc)
+		return ERR_PTR(ENOMEM);
+
+	config_group_init_type_name(&crtc->config_group, name, &crtc_type);
+	crtc->crtc_config_idx = next_idx;
+
+	set_bit(next_idx, &configfs->allocated_crtcs);
+
+	return &crtc->config_group;
+}
+
+static void crtcs_group_drop(struct config_group *group,
+			     struct config_item *item)
+{
+	struct vkms_config_crtc *crtc = item_to_config_crtc(item);
+	kfree(crtc);
+}
+
+static struct configfs_group_operations crtcs_group_ops = {
+	.make_group = &crtcs_group_make,
+	.drop_item = &crtcs_group_drop,
+};
+
+static struct config_item_type crtcs_group_type = {
+	.ct_group_ops = &crtcs_group_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+/* Encoders group: /config/vkms/card/encoders/ */
+
+static struct config_group *encoders_group_make(struct config_group *group,
+						const char *name)
+{
+	struct vkms_configfs *configfs =
+		container_of(group, struct vkms_configfs, encoders_group);
+	unsigned long next_idx = find_first_zero_bit(
+		&configfs->allocated_encoders, VKMS_MAX_OUTPUT_OBJECTS);
+	struct vkms_config_encoder *encoder;
+
+	if (next_idx == VKMS_MAX_OUTPUT_OBJECTS) {
+		DRM_ERROR("Unable to allocate another encoder.");
+		return ERR_PTR(ENOMEM);
+	}
+
+	encoder = kzalloc(sizeof(struct vkms_config_encoder), GFP_KERNEL);
+	if (!encoder)
+		return ERR_PTR(ENOMEM);
+
+	config_group_init_type_name(&encoder->config_group, name,
+				    &encoder_type);
+	add_possible_crtcs(&encoder->config_group,
+			   &encoder->possible_crtcs.group);
+	encoder->encoder_config_idx = next_idx;
+	set_bit(next_idx, &configfs->allocated_encoders);
+
+	return &encoder->config_group;
+}
+
+static void encoders_group_drop(struct config_group *group,
+				struct config_item *item)
+{
+	struct vkms_config_encoder *encoder = item_to_config_encoder(item);
+	kfree(encoder);
+}
+
+static struct configfs_group_operations encoders_group_ops = {
+	.make_group = &encoders_group_make,
+	.drop_item = &encoders_group_drop,
+};
+
+static struct config_item_type encoders_group_type = {
+	.ct_group_ops = &encoders_group_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+/* Planes group: /config/vkms/card/planes/ */
+
+static struct config_group *make_plane_group(struct config_group *group,
+					     const char *name)
+{
+	struct vkms_config_plane *plane =
+		kzalloc(sizeof(struct vkms_config_plane), GFP_KERNEL);
+	if (!plane)
+		return ERR_PTR(ENOMEM);
+
+	config_group_init_type_name(&plane->config_group, name, &plane_type);
+	add_possible_crtcs(&plane->config_group, &plane->possible_crtcs.group);
+
+	return &plane->config_group;
+}
+
+static void drop_plane_group(struct config_group *group,
+			     struct config_item *item)
+{
+	struct vkms_config_plane *plane = item_to_config_plane(item);
+	kfree(plane);
+}
+
+static struct configfs_group_operations plane_group_ops = {
+	.make_group = &make_plane_group,
+	.drop_item = &drop_plane_group,
+};
+
+static struct config_item_type planes_group_type = {
+	.ct_group_ops = &plane_group_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+/* Root directory group, e.g. /config/vkms/card */
+
+static ssize_t card_is_registered_show(struct config_item *item, char *buf)
+{
+	struct vkms_configfs *configfs = item_to_configfs(item);
+	return sprintf(buf, "%d", configfs->card != NULL);
+}
+
+static ssize_t card_is_registered_store(struct config_item *item,
+					const char *buf, size_t len)
+{
+	struct vkms_configfs *configfs = item_to_configfs(item);
+	struct vkms_card *card;
+	int value, ret;
+
+	ret = kstrtoint(buf, 0, &value);
+	if (ret)
+		return ret;
+
+	if (value != 1)
+		return -EINVAL;
+
+	if (configfs->card)
+		return len;
+
+	card = vkms_card_init(item->ci_name, configfs);
+	if (IS_ERR(card))
+		return -PTR_ERR(card);
+
+	return len;
+}
+
+CONFIGFS_ATTR(card_, is_registered);
+
+static struct configfs_attribute *card_group_attrs[] = {
+	&card_attr_is_registered,
+	NULL,
+};
+
+static struct config_item_type card_group_type = {
+	.ct_attrs = card_group_attrs,
+	.ct_owner = THIS_MODULE,
+};
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index 266c9f643f70..37b95ca28672 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -9,6 +9,9 @@
  * the GPU in DRM API tests.
  */
 
+#include <linux/configfs.h>
+#include <linux/device.h>
+#include <linux/dma-mapping.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
@@ -152,7 +155,7 @@ static int vkms_modeset_init(struct vkms_card *card)
 	dev->mode_config.preferred_depth = 0;
 	dev->mode_config.helper_private = &vkms_mode_config_helpers;
 
-	return card->is_default ? vkms_output_init_default(card, 0) : -ENOTSUPP;
+	return card->is_default ? vkms_output_init_default(card, 0) : vkms_output_init(card, 0);
 }
 
 static void vkms_device_destroy(void)
@@ -166,7 +169,7 @@ static void vkms_device_destroy(void)
 	memset(&vkms_device, 0, sizeof(struct vkms_device));
 }
 
-struct vkms_card *vkms_card_init(const char *name, bool is_default)
+struct vkms_card *vkms_card_init(const char *name, struct vkms_configfs *configfs)
 {
 	char unique_name[64] = { 0 };
 	struct platform_device *pdev;
@@ -190,7 +193,7 @@ struct vkms_card *vkms_card_init(const char *name, bool is_default)
 		ret = ENOMEM;
 		goto out_platform_device;
 	}
-
+	
 	card = devm_drm_dev_alloc(&pdev->dev, &vkms_driver, struct vkms_card,
 				  drm);
 	if (IS_ERR(card)) {
@@ -202,7 +205,8 @@ struct vkms_card *vkms_card_init(const char *name, bool is_default)
 	card->platform = pdev;
 	card->drm.unique = card->name_buf;
 	card->vkms_device = &vkms_device;
-	card->is_default = is_default;
+	card->configfs = configfs;
+	card->is_default = configfs == NULL;
 	card->is_registered = false;
 	card->resource_group_id = grp;
 
@@ -235,7 +239,10 @@ struct vkms_card *vkms_card_init(const char *name, bool is_default)
 
 	devres_close_group(&pdev->dev, grp);
 	list_add_tail(&card->node, &vkms_device.cards);
-	
+
+	if (configfs)
+		configfs->card = card;
+
 	return card;
 
 out_release_group:
@@ -260,16 +267,24 @@ void vkms_card_destroy(struct vkms_card *card)
 static int __init vkms_init(void)
 {
 	struct vkms_card *card;
+	int ret;
 
 	vkms_device.config.cursor = enable_cursor;
 	vkms_device.config.writeback = enable_writeback;
 	vkms_device.config.overlay = enable_overlay;
 	INIT_LIST_HEAD(&vkms_device.cards);
+	
+	ret = vkms_init_configfs();
+	if (ret) {
+		DRM_ERROR("Unable to initialize configfs\n");
+		return ret;
+	}
 
 	card = vkms_card_init("default", /* configfs */ NULL);
 	if (IS_ERR(card)) {
-		DRM_ERROR("Unable to init default card");
+		DRM_ERROR("Unable to init default card\n");
 		vkms_device_destroy();
+		vkms_unregister_configfs();
 		return PTR_ERR(card);
 	}
 
@@ -279,6 +294,7 @@ static int __init vkms_init(void)
 static void __exit vkms_exit(void)
 {
 	vkms_device_destroy();
+	vkms_unregister_configfs();
 }
 
 module_init(vkms_init);
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index 30ae06d7af71..f43e4c563863 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -3,6 +3,7 @@
 #ifndef _VKMS_DRV_H_
 #define _VKMS_DRV_H_
 
+#include <linux/configfs.h>
 #include <linux/hrtimer.h>
 #include <linux/kernel.h>
 
@@ -10,6 +11,7 @@
 #include <drm/drm_gem.h>
 #include <drm/drm_gem_atomic_helper.h>
 #include <drm/drm_encoder.h>
+#include <drm/drm_plane.h>
 #include <drm/drm_writeback.h>
 
 #define XRES_MIN    20
@@ -116,11 +118,59 @@ struct vkms_config {
 	bool overlay;
 };
 
+struct vkms_config_links {
+	struct config_group group;
+	unsigned long linked_object_bitmap;
+};
+
+struct vkms_config_connector {
+	struct config_group config_group;
+	struct vkms_config_links possible_encoders;
+};
+
+struct vkms_config_crtc {
+	struct config_group config_group;
+	unsigned long crtc_config_idx;
+};
+
+struct vkms_config_encoder {
+	struct config_group config_group;
+	struct vkms_config_links possible_crtcs;
+	unsigned long encoder_config_idx;
+};
+
+struct vkms_config_plane {
+	struct config_group config_group;
+	struct vkms_config_links possible_crtcs;
+	enum drm_plane_type type;
+};
+
+struct vkms_card;
+
+struct vkms_configfs {
+	/* Directory group containing connector configs, e.g. /config/vkms/card/ */
+	struct config_group card_group;
+	/* Directory group containing connector configs, e.g. /config/vkms/card/connectors/ */
+	struct config_group connectors_group;
+	/* Directory group containing CRTC configs, e.g. /config/vkms/card/crtcs/ */
+	struct config_group crtcs_group;
+	/* Directory group containing encoder configs, e.g. /config/vkms/card/encoders/ */
+	struct config_group encoders_group;
+	/* Directory group containing plane configs, e.g. /config/vkms/card/planes/ */
+	struct config_group planes_group;
+	
+	unsigned long allocated_crtcs;
+	unsigned long allocated_encoders;
+
+	struct vkms_card *card;
+};
+
 struct vkms_card {
 	struct platform_device *platform;
 	struct drm_device drm;
 	struct list_head node;
 	struct vkms_output output;
+	struct vkms_configfs *configfs;
 	struct vkms_device *vkms_device;
 	/* storage for the value of drm->unique, giving this dev a unique busid */
 	char name_buf[64];
@@ -149,8 +199,27 @@ struct vkms_device {
 #define to_vkms_plane_state(target)\
 	container_of(target, struct vkms_plane_state, base.base)
 
+#define item_to_configfs(item)\
+	container_of(to_config_group(item), struct vkms_configfs, card_group)
+
+#define item_to_config_connector(item)\
+	container_of(to_config_group(item), struct vkms_config_connector, config_group)
+
+#define item_to_config_crtc(item) \
+	container_of(to_config_group(item), struct vkms_config_crtc, config_group)
+
+#define item_to_config_encoder(item) \
+	container_of(to_config_group(item), struct vkms_config_encoder, config_group)
+
+#define item_to_config_plane(item) \
+	container_of(to_config_group(item), struct vkms_config_plane, config_group)
+
+#define item_to_config_links(item) \
+	container_of(to_config_group(item), struct vkms_config_links, group)
+
 /* Cards */
-struct vkms_card *vkms_card_init(const char *name, bool is_default);
+struct vkms_card *vkms_card_init(const char *name,
+				 struct vkms_configfs *configfs);
 void vkms_card_destroy(struct vkms_card *card);
 
 /* CRTC */
@@ -176,4 +245,8 @@ void vkms_set_composer(struct vkms_crtc *vkms_crtc, bool enabled);
 /* Writeback */
 int vkms_enable_writeback_connector(struct vkms_card *card, struct vkms_crtc *vkms_crtc);
 
+/* ConfigFS Support */
+int vkms_init_configfs(void);
+void vkms_unregister_configfs(void);
+
 #endif /* _VKMS_DRV_H_ */
diff --git a/drivers/gpu/drm/vkms/vkms_output.c b/drivers/gpu/drm/vkms/vkms_output.c
index 2b72d8e763a8..e343a9c1f311 100644
--- a/drivers/gpu/drm/vkms/vkms_output.c
+++ b/drivers/gpu/drm/vkms/vkms_output.c
@@ -1,10 +1,14 @@
 // SPDX-License-Identifier: GPL-2.0+
 
-#include "vkms_drv.h"
+#include <linux/configfs.h>
+#include <linux/kernel.h>
+
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_probe_helper.h>
 #include <drm/drm_simple_kms_helper.h>
 
+#include "vkms_drv.h"
+
 static void vkms_connector_destroy(struct drm_connector *connector)
 {
 	drm_connector_cleanup(connector);
@@ -171,3 +175,8 @@ int vkms_output_init_default(struct vkms_card *card, int index)
 
 	return ret;
 }
+
+int vkms_output_init(struct vkms_card *card, int index)
+{
+	return -ENOTSUPP;
+}
-- 
2.37.1.359.gd136c6c3e2-goog