[PATCH 3/5] media: vimc: Add the implementation for the configfs api

[Dafna Hirschfeld <dafna.hirschfeld@collabora.com>]

Add the code that implements the usage of configfs in order
to create and configure a device topology from userspace.
The code is only added in this patch but is not used.
It will be used in next patch in the series.

Signed-off-by: Helen Koike <helen.koike@collabora.com>
[refactored for upstream]
Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
---
 drivers/media/platform/vimc/Kconfig         |   9 +-
 drivers/media/platform/vimc/Makefile        |   2 +-
 drivers/media/platform/vimc/vimc-capture.c  |  21 +
 drivers/media/platform/vimc/vimc-common.h   |  46 ++
 drivers/media/platform/vimc/vimc-configfs.c | 656 ++++++++++++++++++++
 drivers/media/platform/vimc/vimc-configfs.h |  41 ++
 drivers/media/platform/vimc/vimc-core.c     |  21 +-
 drivers/media/platform/vimc/vimc-debayer.c  |  22 +
 drivers/media/platform/vimc/vimc-scaler.c   |  26 +-
 drivers/media/platform/vimc/vimc-sensor.c   |  21 +
 10 files changed, 856 insertions(+), 9 deletions(-)
 create mode 100644 drivers/media/platform/vimc/vimc-configfs.c
 create mode 100644 drivers/media/platform/vimc/vimc-configfs.h

diff --git a/drivers/media/platform/vimc/Kconfig b/drivers/media/platform/vimc/Kconfig
index bd221d3e1a4a..6d7836d58ef4 100644
--- a/drivers/media/platform/vimc/Kconfig
+++ b/drivers/media/platform/vimc/Kconfig
@@ -1,15 +1,14 @@
 # SPDX-License-Identifier: GPL-2.0-only
 config VIDEO_VIMC
 	tristate "Virtual Media Controller Driver (VIMC)"
-	depends on VIDEO_DEV && VIDEO_V4L2 && VIDEO_V4L2_SUBDEV_API
+	depends on VIDEO_DEV && VIDEO_V4L2 && VIDEO_V4L2_SUBDEV_API && CONFIGFS_FS
 	select VIDEOBUF2_VMALLOC
 	select VIDEO_V4L2_TPG
 	help
-	  Skeleton driver for Virtual Media Controller
+	  Virtual Media Controller Driver
 
-	  This driver can be compared to the vivid driver for emulating
+	  This driver emulates
 	  a media node that exposes a complex media topology. The topology
-	  is hard coded for now but is meant to be highly configurable in
-	  the future.
+	  is configurable through the configfs API.
 
 	  When in doubt, say N.
diff --git a/drivers/media/platform/vimc/Makefile b/drivers/media/platform/vimc/Makefile
index a53b2b532e9f..eb03d487f308 100644
--- a/drivers/media/platform/vimc/Makefile
+++ b/drivers/media/platform/vimc/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0
 vimc-y := vimc-core.o vimc-common.o vimc-streamer.o vimc-capture.o \
-		vimc-debayer.o vimc-scaler.o vimc-sensor.o
+		vimc-debayer.o vimc-scaler.o vimc-sensor.o  vimc-configfs.o
 
 obj-$(CONFIG_VIDEO_VIMC) += vimc.o
 
diff --git a/drivers/media/platform/vimc/vimc-capture.c b/drivers/media/platform/vimc/vimc-capture.c
index 602f80323031..5cc419e76ce7 100644
--- a/drivers/media/platform/vimc/vimc-capture.c
+++ b/drivers/media/platform/vimc/vimc-capture.c
@@ -9,6 +9,7 @@
 #include <media/videobuf2-core.h>
 #include <media/videobuf2-vmalloc.h>
 
+#include "vimc-configfs.h"
 #include "vimc-common.h"
 #include "vimc-streamer.h"
 
@@ -488,3 +489,23 @@ struct vimc_ent_device *vimc_cap_add(struct vimc_device *vimc,
 
 	return NULL;
 }
+
+static void vimc_cap_create_cfs_pads(struct config_group *ent_group)
+{
+	vimc_cfs_add_sink_pad_api(ent_group, 0, VIMC_CFS_SINK_PAD_NUM(0));
+}
+
+struct vimc_cfs_drv vimc_cap_cfs_drv = {
+	.name = VIMC_CAP_NAME,
+	.create_pads = vimc_cap_create_cfs_pads,
+};
+
+__exit void vimc_cap_exit(void)
+{
+	vimc_cfs_drv_unregister(&vimc_cap_cfs_drv);
+}
+
+__init void vimc_cap_init(void)
+{
+	vimc_cfs_drv_register(&vimc_cap_cfs_drv);
+}
diff --git a/drivers/media/platform/vimc/vimc-common.h b/drivers/media/platform/vimc/vimc-common.h
index 698db7c07645..e0e3b3ab7b19 100644
--- a/drivers/media/platform/vimc/vimc-common.h
+++ b/drivers/media/platform/vimc/vimc-common.h
@@ -14,6 +14,7 @@
 #include <media/v4l2-device.h>
 
 #define VIMC_PDEV_NAME "vimc"
+#define VIMC_MAX_NAME_LEN V4L2_SUBDEV_NAME_SIZE
 
 /* VIMC-specific controls */
 #define VIMC_CID_VIMC_BASE		(0x00f00000 | 0xf000)
@@ -31,6 +32,11 @@
 #define VIMC_IS_SRC(pad)	(pad)
 #define VIMC_IS_SINK(pad)	(!(pad))
 
+#define VIMC_DEB_NAME "vimc-debayer"
+#define VIMC_SEN_NAME "vimc-sensor"
+#define VIMC_SCA_NAME "vimc-scaler"
+#define VIMC_CAP_NAME "vimc-capture"
+
 /**
  * struct vimc_colorimetry_clamp - Adjust colorimetry parameters
  *
@@ -72,6 +78,18 @@ struct vimc_platform_data {
 	char entity_name[32];
 };
 
+/**
+ * struct vimc_platform_data_core - platform data to the core
+ *
+ * @ents: list of vimc_entity_data objects allocated by the configfs
+ * @links: list of vimc_links objects allocated by the configfs
+ *
+ */
+struct vimc_platform_data_core {
+	struct list_head *ents;
+	struct list_head *links;
+};
+
 /**
  * struct vimc_pix_map - maps media bus code with v4l2 pixel format
  *
@@ -92,6 +110,8 @@ struct vimc_pix_map {
 /**
  * struct vimc_ent_device - core struct that represents a node in the topology
  *
+ * @name:		the name of the entity
+ * @drv_name:		the name of the driver of the entity
  * @ent:		the pointer to struct media_entity for the node
  * @pads:		the list of pads of the node
  * @process_frame:	callback send a frame to that node
@@ -108,12 +128,30 @@ struct vimc_pix_map {
  * media_entity
  */
 struct vimc_ent_device {
+	char name[VIMC_MAX_NAME_LEN];
+	char drv_name[VIMC_MAX_NAME_LEN];
 	struct media_entity *ent;
 	struct media_pad *pads;
 	void * (*process_frame)(struct vimc_ent_device *ved,
 				const void *frame);
 	void (*vdev_get_format)(struct vimc_ent_device *ved,
 			      struct v4l2_pix_format *fmt);
+	struct list_head list;
+};
+
+struct vimc_entity_data {
+	char name[VIMC_MAX_NAME_LEN];
+	char drv_name[VIMC_MAX_NAME_LEN];
+	struct list_head list;
+};
+
+struct vimc_link {
+	char source_name[VIMC_MAX_NAME_LEN];
+	char sink_name[VIMC_MAX_NAME_LEN];
+	u16 source_pad;
+	u16 sink_pad;
+	u32 flags;
+	struct list_head list;
 };
 
 /**
@@ -156,18 +194,26 @@ struct vimc_ent_config {
 struct vimc_ent_device *vimc_cap_add(struct vimc_device *vimc,
 				     const char *vcfg_name);
 void vimc_cap_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
+void vimc_cap_init(void);
+void vimc_cap_exit(void);
 
 struct vimc_ent_device *vimc_deb_add(struct vimc_device *vimc,
 				     const char *vcfg_name);
 void vimc_deb_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
+void vimc_deb_init(void);
+void vimc_deb_exit(void);
 
 struct vimc_ent_device *vimc_sca_add(struct vimc_device *vimc,
 				     const char *vcfg_name);
 void vimc_sca_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
+void vimc_sca_init(void);
+void vimc_sca_exit(void);
 
 struct vimc_ent_device *vimc_sen_add(struct vimc_device *vimc,
 				     const char *vcfg_name);
 void vimc_sen_rm(struct vimc_device *vimc, struct vimc_ent_device *ved);
+void vimc_sen_init(void);
+void vimc_sen_exit(void);
 
 /**
  * vimc_pads_init - initialize pads
diff --git a/drivers/media/platform/vimc/vimc-configfs.c b/drivers/media/platform/vimc/vimc-configfs.c
new file mode 100644
index 000000000000..933aece0bb5f
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-configfs.c
@@ -0,0 +1,656 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * vimc-configfs.c Virtual Media Controller Driver
+ *
+ * Copyright (C) 2018 Helen Koike <helen.koike@collabora.com>
+ */
+
+#include <linux/platform_device.h>
+
+#include "vimc-common.h"
+#include "vimc-configfs.h"
+
+#define CHAR_SEPARATOR ':'
+#define CFS_SUBSYS_NAME "vimc"
+#define MAX_PAD_DIGI_NUM 4
+
+#define ci_err(ci, fmt, ...) \
+	pr_err("vimc: %s: " pr_fmt(fmt), (ci)->ci_name, ##__VA_ARGS__)
+#define cg_err(cg, ...) ci_err(&(cg)->cg_item, ##__VA_ARGS__)
+#define ci_warn(ci, fmt, ...) \
+	pr_warn("vimc: %s: " pr_fmt(fmt), (ci)->ci_name, ##__VA_ARGS__)
+#define cg_warn(cg, ...) ci_warn(&(cg)->cg_item, ##__VA_ARGS__)
+#define ci_dbg(ci, fmt, ...) \
+	pr_debug("vimc: %s: %s:" pr_fmt(fmt), (ci)->ci_name, __func__, ##__VA_ARGS__)
+#define cg_dbg(cg, ...) ci_dbg(&(cg)->cg_item, ##__VA_ARGS__)
+
+#define IS_PLUGGED(cfs) (!!(cfs)->pdev)
+
+// currently there is no entity with more than two pads, this will
+// change when adding the splitter entity
+#define VIMC_ENT_MAX_PADS 2
+
+enum vimc_cfs_hotplug_state {
+	VIMC_CFS_HOTPLUG_STATE_UNPLUGGED = 0,
+	VIMC_CFS_HOTPLUG_STATE_PLUGGED = 1,
+};
+
+const static char *vimc_cfs_hotplug_values[2][3] = {
+	[VIMC_CFS_HOTPLUG_STATE_UNPLUGGED] = {"unplugged\n", "unplug\n", "0\n"},
+	[VIMC_CFS_HOTPLUG_STATE_PLUGGED] = {"plugged\n", "plug\n", "1\n"},
+};
+
+/* --------------------------------------------------------------------------
+ * Pipeline structures
+ */
+
+static struct vimc_cfs_subsystem {
+	struct configfs_subsystem subsys;
+	struct list_head drvs;
+} vimc_cfs_subsys;
+
+/* Structure which describes the whole topology */
+struct vimc_cfs_device {
+	struct list_head ents;
+	struct list_head links;
+	struct platform_device *pdev;
+	struct vimc_platform_data_core pdata;
+	struct config_group gdev;
+};
+
+/* Structure which describes individual configuration for each entity */
+struct vimc_cfs_ent {
+	struct vimc_entity_data ent;
+	struct config_group cg;
+	struct config_group pad_groups[VIMC_ENT_MAX_PADS];
+};
+
+struct vimc_cfs_link {
+	struct vimc_link link;
+	struct config_item ci;
+};
+
+void vimc_cfs_drv_register(struct vimc_cfs_drv *c_drv)
+{
+	pr_debug("%s: adding driver %s\n", __func__, c_drv->name);
+	list_add(&c_drv->list, &vimc_cfs_subsys.drvs);
+}
+EXPORT_SYMBOL_GPL(vimc_cfs_drv_register);
+
+void vimc_cfs_drv_unregister(struct vimc_cfs_drv *c_drv)
+{
+	pr_debug("%s: removing driver %s\n", __func__, c_drv->name);
+	list_del(&c_drv->list);
+}
+EXPORT_SYMBOL_GPL(vimc_cfs_drv_unregister);
+
+/* --------------------------------------------------------------------------
+ * Platform Device builders
+ */
+
+static void vimc_cfs_device_unplug(struct vimc_cfs_device *cfs)
+{
+	dev_dbg(&cfs->pdev->dev, "Unplugging device\n");
+	platform_device_unregister(cfs->pdev);
+
+	cfs->pdev = NULL;
+}
+
+static int vimc_cfs_device_plug(struct vimc_cfs_device *cfs)
+{
+	cg_dbg(&cfs->gdev, "Plugging device\n");
+
+	if (list_empty(&cfs->ents)) {
+		cg_warn(&cfs->gdev,
+			"At least one entity is required to plug the device\n");
+		return -EINVAL;
+	}
+
+	cfs->pdev = platform_device_register_data(NULL, "vimc-core",
+						  PLATFORM_DEVID_AUTO,
+						  &cfs->pdata,
+						  sizeof(cfs->pdata));
+	if (IS_ERR(cfs->pdev)) {
+		int ret = PTR_ERR(cfs->pdev);
+
+		cfs->pdev = NULL;
+		return ret;
+	}
+
+	return 0;
+}
+
+/* --------------------------------------------------------------------------
+ * Links
+ */
+
+static ssize_t vimc_cfs_link_store_flag(struct config_item *item,
+					const char *buf,
+					size_t size, u32 flag)
+{
+	struct vimc_cfs_link *c_link =
+		container_of(item, struct vimc_cfs_link, ci);
+
+	if (!strncmp(buf, "on\n", 4) || !strncmp(buf, "1\n", 3)) {
+		c_link->link.flags |= MEDIA_LNK_FL_ENABLED;
+		return strlen(buf);
+	} else if (!strncmp(buf, "off\n", 5) || !strncmp(buf, "0\n", 3)) {
+		c_link->link.flags &= ~MEDIA_LNK_FL_ENABLED;
+		return strlen(buf);
+	}
+	return -EINVAL;
+}
+
+static ssize_t vimc_cfs_link_show_flag(struct config_item *item,
+				       char *buf, u32 flag)
+{
+	struct vimc_cfs_link *c_link = container_of(item,
+						    struct vimc_cfs_link, ci);
+
+	if (c_link->link.flags & flag)
+		strscpy(buf, "on\n", 4);
+	else
+		strscpy(buf, "off\n", 5);
+	return strlen(buf);
+}
+
+static ssize_t vimc_cfs_link_enabled_store(struct config_item *item,
+					   const char *buf,
+					   size_t size)
+{
+	return vimc_cfs_link_store_flag(item, buf, size, MEDIA_LNK_FL_ENABLED);
+}
+
+
+static ssize_t vimc_cfs_link_enabled_show(struct config_item *item,
+					  char *buf)
+{
+	return vimc_cfs_link_show_flag(item, buf, MEDIA_LNK_FL_ENABLED);
+}
+
+CONFIGFS_ATTR(vimc_cfs_link_, enabled);
+
+static ssize_t vimc_cfs_link_immutable_show(struct config_item *item,
+						 char *buf)
+{
+	return vimc_cfs_link_show_flag(item, buf, MEDIA_LNK_FL_IMMUTABLE);
+}
+
+static ssize_t vimc_cfs_link_immutable_store(struct config_item *item,
+						   const char *buf, size_t size)
+{
+	return vimc_cfs_link_store_flag(item, buf, size,
+					MEDIA_LNK_FL_IMMUTABLE);
+}
+
+CONFIGFS_ATTR(vimc_cfs_link_, immutable);
+
+static void vimc_cfs_fill_link_data(struct config_item *src,
+				struct config_item *target)
+{
+	struct config_item *src_ent_ci = src->ci_parent->ci_parent;
+	struct config_item *trgt_ent_ci = target->ci_parent;
+	struct vimc_cfs_link *c_link =
+			container_of(src, struct vimc_cfs_link, ci);
+	struct vimc_cfs_ent *vimc_src_ent = container_of(src_ent_ci,
+							 struct vimc_cfs_ent,
+							 cg.cg_item);
+	struct vimc_cfs_ent *vimc_trgt_ent = container_of(trgt_ent_ci,
+							 struct vimc_cfs_ent,
+							 cg.cg_item);
+	struct vimc_cfs_device *cfs = container_of(src_ent_ci->ci_parent,
+							 struct vimc_cfs_device,
+							 gdev.cg_item);
+
+	if (IS_PLUGGED(cfs))
+		vimc_cfs_device_unplug(cfs);
+
+	/* src and target validation already done in the allow_link callback,
+	 * so there is no need to check sscanf result
+	 */
+	sscanf(src->ci_parent->ci_name, VIMC_CFS_SRC_PAD "%hu",
+	       &c_link->link.source_pad);
+	sscanf(target->ci_parent->ci_name, VIMC_CFS_SINK_PAD "%hu",
+	       &c_link->link.sink_pad);
+
+	strscpy(c_link->link.source_name, vimc_src_ent->ent.name,
+		sizeof(c_link->link.source_name));
+	strscpy(c_link->link.sink_name, vimc_trgt_ent->ent.name,
+		sizeof(c_link->link.sink_name));
+
+	cg_dbg(&cfs->gdev, "creating link %s:%u->%s:%u\n",
+			c_link->link.source_name, c_link->link.source_pad,
+			c_link->link.sink_name, c_link->link.sink_pad);
+
+	list_add(&c_link->link.list, &cfs->links);
+}
+
+static void vimc_cfs_drop_link(struct config_item *src,
+			       struct config_item *target)
+{
+	struct vimc_cfs_link *c_link = container_of(src,
+						    struct vimc_cfs_link, ci);
+
+	ci_dbg(&c_link->ci, "dropping link %s:%u->%s:%u\n",
+	       c_link->link.source_name, c_link->link.source_pad,
+	       c_link->link.sink_name, c_link->link.sink_pad);
+
+	c_link->link.source_pad = 0;
+	c_link->link.sink_pad = 0;
+	memset(c_link->link.source_name, 0, sizeof(c_link->link.source_name));
+	memset(c_link->link.sink_name, 0, sizeof(c_link->link.sink_name));
+	list_del(&c_link->link.list);
+}
+
+int vimc_cfs_allow_link(struct config_item *src, struct config_item *target)
+{
+	struct config_item *s = src;
+	struct config_item *t = target;
+	struct config_item *src_ent_ci, *trgt_ent_ci;
+	int i;
+	int ret = 0;
+	struct configfs_subsystem *subsys = &vimc_cfs_subsys.subsys;
+
+	if (strncmp(target->ci_name, VIMC_CFS_SINK_PAD,
+		    sizeof(VIMC_CFS_SINK_PAD) - 1)) {
+		ci_warn(src, "link target (%s) does not start with '%s'\n",
+			target->ci_name, VIMC_CFS_SINK_PAD);
+		return -EINVAL;
+	}
+
+	mutex_lock(&subsys->su_mutex);
+	for (i = 0; i < 3; i++)
+		s = s->ci_parent;
+
+	for (i = 0; i < 2; i++) {
+		t = t->ci_parent;
+		if (!t) {
+			ci_warn(src, "link target (%s) is not a sink pad\n",
+				target->ci_name);
+			ret = -EINVAL;
+			goto end;
+		}
+	}
+
+	if (s != t) {
+		ci_warn(src, "not allow linking between different vimcs devices: (%s) and (%s)\n",
+			s->ci_name, t->ci_name);
+		ret = -EINVAL;
+		goto end;
+	}
+	src_ent_ci = src->ci_parent->ci_parent;
+	trgt_ent_ci = target->ci_parent;
+	if (src_ent_ci == trgt_ent_ci) {
+		ci_warn(src, "both pads belong to the same entity (%s) - this is not allowed\n",
+				src_ent_ci->ci_name);
+		ret = -EINVAL;
+		goto end;
+	}
+
+	vimc_cfs_fill_link_data(src, target);
+end:
+	mutex_unlock(&subsys->su_mutex);
+	return ret;
+}
+
+static void vimc_cfs_prepare_link_release(struct config_item *item)
+{
+	struct vimc_cfs_link *c_link = container_of(item,
+						    struct vimc_cfs_link, ci);
+
+	ci_dbg(item, "releasing link '%s'", item->ci_name);
+	kfree(c_link);
+}
+
+static struct configfs_attribute *vimc_cfs_link_attrs[] = {
+	&vimc_cfs_link_attr_enabled,
+	&vimc_cfs_link_attr_immutable,
+	NULL,
+};
+
+static struct configfs_item_operations vimc_cfs_allow_link_item_ops = {
+	.allow_link = vimc_cfs_allow_link,
+	.drop_link = vimc_cfs_drop_link,
+	.release = vimc_cfs_prepare_link_release,
+};
+
+struct config_item_type vimc_cfs_allow_link_type = {
+	.ct_owner = THIS_MODULE,
+	.ct_item_ops = &vimc_cfs_allow_link_item_ops,
+	.ct_attrs = vimc_cfs_link_attrs,
+};
+
+/* --------------------------------------------------------------------------
+ * Source pad instance
+ */
+
+static void vimc_cfs_src_pad_prepare_link_drop_item(
+		struct config_group *src_pad_group,
+		struct config_item *link_item)
+{
+
+	struct config_item *cfs_item;
+	struct vimc_cfs_device *cfs;
+
+	cfs_item = src_pad_group->cg_item.ci_parent->ci_parent;
+	cfs = container_of(cfs_item->ci_parent, struct vimc_cfs_device,
+			   gdev.cg_item);
+	cg_dbg(&cfs->gdev, "dropping prepared link '%s'\n",
+	       link_item->ci_name);
+	if (IS_PLUGGED(cfs))
+		vimc_cfs_device_unplug(cfs);
+	config_item_put(link_item);
+}
+
+static struct config_item *vimc_cfs_src_pad_prepare_link_make_item(
+			   struct config_group *group,
+			   const char *name)
+{
+	struct vimc_cfs_link *c_link = kzalloc(sizeof(*c_link), GFP_KERNEL);
+
+	cg_dbg(group, "link name is '%s'\n", name);
+	config_item_init_type_name(&c_link->ci, name,
+				   &vimc_cfs_allow_link_type);
+	return &c_link->ci;
+}
+struct config_item_type vimc_cfs_empty_type = {
+	.ct_owner = THIS_MODULE,
+};
+
+static struct configfs_group_operations vimc_cfs_src_pad_ops = {
+	.make_item = vimc_cfs_src_pad_prepare_link_make_item,
+	.drop_item = vimc_cfs_src_pad_prepare_link_drop_item
+};
+
+struct config_item_type vimc_cfs_src_pad_type = {
+	.ct_owner = THIS_MODULE,
+	.ct_group_ops = &vimc_cfs_src_pad_ops,
+};
+
+/* --------------------------------------------------------------------------
+ * Device instance
+ */
+
+static void vimc_cfs_ent_release(struct config_item *item)
+{
+	struct vimc_cfs_ent *c_ent = container_of(item, struct vimc_cfs_ent,
+	cg.cg_item);
+
+	ci_dbg(item, "releasing entity '%s' of driver '%s'",
+	       c_ent->ent.name,
+	       c_ent->ent.drv_name);
+	kfree(c_ent);
+}
+
+static struct configfs_item_operations vimc_cfs_ent_item_ops = {
+	.release	= vimc_cfs_ent_release,
+};
+
+struct config_item_type vimc_cfs_ent_type = {
+	.ct_owner = THIS_MODULE,
+	.ct_item_ops = &vimc_cfs_ent_item_ops,
+};
+
+void vimc_cfs_add_sink_pad_api(struct config_group *ent_group,
+					int pad_idx, const char *name)
+{
+	struct vimc_cfs_ent *c_ent = container_of(ent_group,
+						  struct vimc_cfs_ent, cg);
+
+	config_group_init_type_name(&c_ent->pad_groups[pad_idx], name,
+				    &vimc_cfs_empty_type);
+	configfs_add_default_group(&c_ent->pad_groups[pad_idx], ent_group);
+}
+EXPORT_SYMBOL_GPL(vimc_cfs_add_sink_pad_api);
+
+void vimc_cfs_add_source_pad_api(struct config_group *ent_group,
+					  int pad_idx, const char *name)
+{
+	struct vimc_cfs_ent *c_ent = container_of(ent_group,
+						  struct vimc_cfs_ent, cg);
+
+	config_group_init_type_name(&c_ent->pad_groups[pad_idx], name,
+				    &vimc_cfs_src_pad_type);
+	configfs_add_default_group(&c_ent->pad_groups[pad_idx], ent_group);
+}
+EXPORT_SYMBOL_GPL(vimc_cfs_add_source_pad_api);
+
+static void vimc_cfs_dev_drop_ent_item(struct config_group *dev_group,
+					   struct config_item *ent_item)
+{
+	struct vimc_cfs_ent *c_ent = container_of(ent_item, struct vimc_cfs_ent,
+						  cg.cg_item);
+	struct vimc_cfs_device *cfs = container_of(dev_group,
+						   struct vimc_cfs_device,
+						   gdev);
+
+	if (IS_PLUGGED(cfs))
+		vimc_cfs_device_unplug(cfs);
+
+	cg_dbg(&cfs->gdev, "dropping entity '%s' of driver '%s'",
+	       c_ent->ent.name, c_ent->ent.drv_name);
+	list_del(&c_ent->ent.list);
+	config_item_put(ent_item);
+}
+
+static struct config_group *vimc_cfs_dev_make_ent_group(
+			struct config_group *group, const char *name)
+{
+	struct vimc_cfs_device *cfs = container_of(group,
+						   struct vimc_cfs_device,
+						   gdev);
+	char *ent_name, *sep = strchr(name, CHAR_SEPARATOR);
+	struct vimc_cfs_ent *c_ent;
+	struct vimc_entity_data *ent;
+	size_t drv_namelen;
+	struct vimc_cfs_drv *c_drv = NULL;
+
+	cg_dbg(group, "trying to make entity '%s'\n", name);
+	if (IS_PLUGGED(cfs))
+		vimc_cfs_device_unplug(cfs);
+
+	/* Parse format "drv_name:ent_name" */
+	if (!sep) {
+		cg_warn(&cfs->gdev,
+			"Could not find separator '%c'\n", CHAR_SEPARATOR);
+		goto syntax_error;
+	}
+	drv_namelen = (size_t)(sep - name);
+	ent_name = &sep[1];
+	if (!*ent_name || !drv_namelen) {
+		cg_warn(&cfs->gdev,
+			"%s: Driver name and entity name can't be empty.\n",
+		       name);
+		goto syntax_error;
+	}
+	if (drv_namelen >= VIMC_MAX_NAME_LEN) {
+		cg_err(&cfs->gdev,
+		       "%s: Driver name length should be less than %u.\n",
+		       name, VIMC_MAX_NAME_LEN);
+		goto syntax_error;
+	}
+	list_for_each_entry(ent, &cfs->ents, list) {
+		if (!strncmp(ent->name, ent_name, sizeof(ent->name))) {
+			cg_err(&cfs->gdev, "entity `%s` already exist\n",
+			       ent->name);
+			goto syntax_error;
+		}
+	}
+
+	c_ent = kzalloc(sizeof(*c_ent), GFP_KERNEL);
+	if (!c_ent)
+		return ERR_PTR(-ENOMEM);
+
+	strscpy(c_ent->ent.drv_name, name, drv_namelen + 1);
+	strscpy(c_ent->ent.name, ent_name, sizeof(c_ent->ent.name));
+
+	/* Configure group */
+
+	/* TODO: add support for hotplug at entity level */
+	list_for_each_entry(c_drv, &vimc_cfs_subsys.drvs, list) {
+		if (!strcmp(c_ent->ent.drv_name, c_drv->name)) {
+			config_group_init_type_name(&c_ent->cg, name,
+						    &vimc_cfs_ent_type);
+			if (c_drv->create_pads)
+				c_drv->create_pads(&c_ent->cg);
+			list_add(&c_ent->ent.list, &cfs->ents);
+			return &c_ent->cg;
+		}
+	}
+	cg_warn(&cfs->gdev, "entity type %s not found\n", c_ent->ent.drv_name);
+	kfree(c_ent);
+	return ERR_PTR(-EINVAL);
+
+syntax_error:
+	cg_err(&cfs->gdev,
+		"couldn't create entity %s, wrong syntax.", name);
+	return ERR_PTR(-EINVAL);
+}
+
+static int vimc_cfs_decode_state(const char *buf, size_t size)
+{
+	unsigned int i, j;
+
+	for (i = 0; i < ARRAY_SIZE(vimc_cfs_hotplug_values); i++) {
+		for (j = 0; j < ARRAY_SIZE(vimc_cfs_hotplug_values[0]); j++) {
+			if (!strncmp(buf, vimc_cfs_hotplug_values[i][j], size))
+				return i;
+		}
+	}
+	return -EINVAL;
+}
+
+static ssize_t vimc_cfs_dev_hotplug_show(struct config_item *item,
+					      char *buf)
+{
+	struct vimc_cfs_device *cfs = container_of(item, struct vimc_cfs_device,
+						   gdev.cg_item);
+
+	strcpy(buf, vimc_cfs_hotplug_values[IS_PLUGGED(cfs)][0]);
+	return strlen(buf);
+}
+
+static int vimc_cfs_hotplug_set(struct vimc_cfs_device *cfs,
+				enum vimc_cfs_hotplug_state state)
+{
+	if (state == IS_PLUGGED(cfs)) {
+		return 0;
+	} else if (state == VIMC_CFS_HOTPLUG_STATE_UNPLUGGED) {
+		vimc_cfs_device_unplug(cfs);
+		return 0;
+	} else if (state == VIMC_CFS_HOTPLUG_STATE_PLUGGED) {
+		return vimc_cfs_device_plug(cfs);
+	}
+	return -EINVAL;
+}
+
+static ssize_t vimc_cfs_dev_hotplug_store(struct config_item *item,
+					       const char *buf, size_t size)
+{
+	struct vimc_cfs_device *cfs = container_of(item, struct vimc_cfs_device,
+						   gdev.cg_item);
+	int state = vimc_cfs_decode_state(buf, size);
+
+	if (vimc_cfs_hotplug_set(cfs, state))
+		return -EINVAL;
+	return size;
+}
+
+CONFIGFS_ATTR(vimc_cfs_dev_, hotplug);
+
+static void vimc_cfs_dev_release(struct config_item *item)
+{
+	struct vimc_cfs_device *cfs = container_of(item, struct vimc_cfs_device,
+						   gdev.cg_item);
+
+	ci_dbg(item, "releasing dev %s\n", item->ci_name);
+	kfree(cfs);
+}
+
+static struct configfs_group_operations vimc_cfs_dev_group_ops = {
+	.make_group = vimc_cfs_dev_make_ent_group,
+	.drop_item = vimc_cfs_dev_drop_ent_item,
+};
+
+static struct configfs_item_operations vimc_cfs_dev_item_ops = {
+	.release = vimc_cfs_dev_release,
+};
+
+static struct configfs_attribute *vimc_cfs_dev_attrs[] = {
+	&vimc_cfs_dev_attr_hotplug,
+	NULL,
+};
+
+static struct config_item_type vimc_cfs_dev_type = {
+	.ct_group_ops = &vimc_cfs_dev_group_ops,
+	.ct_item_ops = &vimc_cfs_dev_item_ops,
+	.ct_attrs = vimc_cfs_dev_attrs,
+	.ct_owner = THIS_MODULE,
+};
+
+/* --------------------------------------------------------------------------
+ * Subsystem
+ * --------------------------------------------------------------------------
+ */
+
+static void vimc_cfs_subsys_drop_dev_item(struct config_group *group,
+				   struct config_item *item)
+{
+	struct vimc_cfs_device *cfs = container_of(to_config_group(item),
+						   struct vimc_cfs_device,
+						   gdev);
+
+	if (IS_PLUGGED(cfs))
+		vimc_cfs_device_unplug(cfs);
+	cg_dbg(&cfs->gdev, "dropping subsys '%s'", item->ci_name);
+	config_item_put(item);
+}
+
+static struct config_group *vimc_cfs_subsys_make_dev_group(
+				struct config_group *group, const char *name)
+{
+	struct vimc_cfs_device *cfs = kzalloc(sizeof(*cfs), GFP_KERNEL);
+
+	if (!cfs)
+		return ERR_PTR(-ENOMEM);
+
+	cg_dbg(&cfs->gdev, "making dev group '%s'", name);
+	/* Configure platform data */
+	INIT_LIST_HEAD(&cfs->ents);
+	INIT_LIST_HEAD(&cfs->links);
+	cfs->pdata.links = &cfs->links;
+	cfs->pdata.ents = &cfs->ents;
+
+	config_group_init_type_name(&cfs->gdev, name, &vimc_cfs_dev_type);
+
+	return &cfs->gdev;
+}
+
+static struct configfs_group_operations vimc_cfs_subsys_group_ops = {
+	.make_group	= vimc_cfs_subsys_make_dev_group,
+	.drop_item	= vimc_cfs_subsys_drop_dev_item,
+};
+
+static struct config_item_type vimc_cfs_subsys_type = {
+	.ct_group_ops = &vimc_cfs_subsys_group_ops,
+	.ct_owner = THIS_MODULE,
+};
+
+int vimc_cfs_subsys_register(void)
+{
+	struct configfs_subsystem *subsys = &vimc_cfs_subsys.subsys;
+	int ret;
+
+	INIT_LIST_HEAD(&vimc_cfs_subsys.drvs);
+	config_group_init_type_name(&subsys->su_group, CFS_SUBSYS_NAME,
+				    &vimc_cfs_subsys_type);
+	mutex_init(&subsys->su_mutex);
+	ret = configfs_register_subsystem(subsys);
+
+	return ret;
+}
+
+void vimc_cfs_subsys_unregister(void)
+{
+	configfs_unregister_subsystem(&vimc_cfs_subsys.subsys);
+}
diff --git a/drivers/media/platform/vimc/vimc-configfs.h b/drivers/media/platform/vimc/vimc-configfs.h
new file mode 100644
index 000000000000..0d3afdb31fdd
--- /dev/null
+++ b/drivers/media/platform/vimc/vimc-configfs.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * vimc-configfs.h Virtual Media Controller Driver
+ *
+ * Copyright (C) 2018 Helen Koike <helen.koike@collabora.com>
+ */
+
+#ifndef _VIMC_CONFIGFS_H_
+#define _VIMC_CONFIGFS_H_
+
+#include <linux/configfs.h>
+
+#define VIMC_CFS_SRC_PAD "pad:source:"
+#define VIMC_CFS_SINK_PAD "pad:sink:"
+
+#define VIMC_CFS_SRC_PAD_NUM(n) "pad:source:" #n
+#define VIMC_CFS_SINK_PAD_NUM(n) "pad:sink:" #n
+
+extern struct config_item_type vimc_default_cfs_pad_type;
+
+void vimc_cfs_add_source_pad_api(struct config_group *ent_group,
+					int pad_idx, const char *name);
+
+void vimc_cfs_add_sink_pad_api(struct config_group *ent_group,
+				      int pad_idx, const char *name);
+struct vimc_cfs_drv {
+	const char *name;
+	struct list_head list;
+
+	void (*const create_pads)(struct config_group *parent);
+};
+
+int vimc_cfs_subsys_register(void);
+
+void vimc_cfs_subsys_unregister(void);
+
+void vimc_cfs_drv_register(struct vimc_cfs_drv *c_drv);
+
+void vimc_cfs_drv_unregister(struct vimc_cfs_drv *c_drv);
+
+#endif
diff --git a/drivers/media/platform/vimc/vimc-core.c b/drivers/media/platform/vimc/vimc-core.c
index 6e3e5c91ae39..476bad2cb2de 100644
--- a/drivers/media/platform/vimc/vimc-core.c
+++ b/drivers/media/platform/vimc/vimc-core.c
@@ -15,6 +15,8 @@
 
 #define VIMC_MDEV_MODEL_NAME "VIMC MDEV"
 
+#include "vimc-configfs.h"
+
 #define VIMC_ENT_LINK(src, srcpad, sink, sinkpad, link_flags) {	\
 	.src_ent = src,						\
 	.src_pad = srcpad,					\
@@ -335,13 +337,30 @@ static int __init vimc_init(void)
 		return ret;
 	}
 
+	ret = vimc_cfs_subsys_register();
+	if (ret) {
+		pr_err("%s: configfs subsys registration failed (%d)\n",
+		       __func__, ret);
+		platform_driver_unregister(&vimc_pdrv);
+		return ret;
+	}
+
+	vimc_sen_init();
+	vimc_deb_init();
+	vimc_sca_init();
+	vimc_cap_init();
 	return 0;
 }
 
 static void __exit vimc_exit(void)
 {
-	platform_driver_unregister(&vimc_pdrv);
+	vimc_sen_exit();
+	vimc_deb_exit();
+	vimc_sca_exit();
+	vimc_cap_exit();
 
+	vimc_cfs_subsys_unregister();
+	platform_driver_unregister(&vimc_pdrv);
 	platform_device_unregister(&vimc_dev.pdev);
 }
 
diff --git a/drivers/media/platform/vimc/vimc-debayer.c b/drivers/media/platform/vimc/vimc-debayer.c
index feac47d79449..e461b155e514 100644
--- a/drivers/media/platform/vimc/vimc-debayer.c
+++ b/drivers/media/platform/vimc/vimc-debayer.c
@@ -12,6 +12,7 @@
 #include <media/v4l2-subdev.h>
 
 #include "vimc-common.h"
+#include "vimc-configfs.h"
 
 static unsigned int deb_mean_win_size = 3;
 module_param(deb_mean_win_size, uint, 0000);
@@ -533,3 +534,24 @@ struct vimc_ent_device *vimc_deb_add(struct vimc_device *vimc,
 
 	return &vdeb->ved;
 }
+
+static void vimc_deb_create_cfs_pads(struct config_group *ent_group)
+{
+	vimc_cfs_add_source_pad_api(ent_group, 0, VIMC_CFS_SRC_PAD_NUM(1));
+	vimc_cfs_add_sink_pad_api(ent_group, 1, VIMC_CFS_SINK_PAD_NUM(0));
+}
+
+struct vimc_cfs_drv vimc_deb_cfs_drv = {
+	.name = VIMC_DEB_NAME,
+	.create_pads = vimc_deb_create_cfs_pads,
+};
+
+__exit void vimc_deb_exit(void)
+{
+	vimc_cfs_drv_unregister(&vimc_deb_cfs_drv);
+}
+
+__init void vimc_deb_init(void)
+{
+	vimc_cfs_drv_register(&vimc_deb_cfs_drv);
+}
diff --git a/drivers/media/platform/vimc/vimc-scaler.c b/drivers/media/platform/vimc/vimc-scaler.c
index a6a3cc5be872..e5cf0073d68a 100644
--- a/drivers/media/platform/vimc/vimc-scaler.c
+++ b/drivers/media/platform/vimc/vimc-scaler.c
@@ -10,6 +10,7 @@
 #include <linux/v4l2-mediabus.h>
 #include <media/v4l2-subdev.h>
 
+#include "vimc-configfs.h"
 #include "vimc-common.h"
 
 static unsigned int sca_mult = 3;
@@ -373,14 +374,35 @@ struct vimc_ent_device *vimc_sca_add(struct vimc_device *vimc,
 				   &vimc_sca_int_ops, &vimc_sca_ops);
 	if (ret) {
 		kfree(vsca);
-		return NULL;
+		return ERR_PTR(ret);
 	}
 
 	vsca->ved.process_frame = vimc_sca_process_frame;
-	vsca->dev = &vimc->pdev.dev;
+	vsca->dev = vimc->mdev.dev;
 
 	/* Initialize the frame format */
 	vsca->sink_fmt = sink_fmt_default;
 
 	return &vsca->ved;
 }
+
+static void vimc_sca_create_cfs_pads(struct config_group *ent_group)
+{
+	vimc_cfs_add_source_pad_api(ent_group, 0, VIMC_CFS_SRC_PAD_NUM(1));
+	vimc_cfs_add_sink_pad_api(ent_group, 1, VIMC_CFS_SINK_PAD_NUM(0));
+}
+
+struct vimc_cfs_drv vimc_sca_cfs_drv = {
+	.name = VIMC_SCA_NAME,
+	.create_pads = vimc_sca_create_cfs_pads,
+};
+
+__exit void vimc_sca_exit(void)
+{
+	vimc_cfs_drv_unregister(&vimc_sca_cfs_drv);
+}
+
+__init void vimc_sca_init(void)
+{
+	vimc_cfs_drv_register(&vimc_sca_cfs_drv);
+}
diff --git a/drivers/media/platform/vimc/vimc-sensor.c b/drivers/media/platform/vimc/vimc-sensor.c
index 46dc6a535abe..22e3ad98c818 100644
--- a/drivers/media/platform/vimc/vimc-sensor.c
+++ b/drivers/media/platform/vimc/vimc-sensor.c
@@ -12,6 +12,7 @@
 #include <media/v4l2-subdev.h>
 #include <media/tpg/v4l2-tpg.h>
 
+#include "vimc-configfs.h"
 #include "vimc-common.h"
 
 struct vimc_sen_device {
@@ -391,3 +392,23 @@ struct vimc_ent_device *vimc_sen_add(struct vimc_device *vimc,
 
 	return NULL;
 }
+
+static void vimc_sen_create_cfs_pads(struct config_group *ent_group)
+{
+	vimc_cfs_add_source_pad_api(ent_group, 0, VIMC_CFS_SRC_PAD_NUM(0));
+}
+
+struct vimc_cfs_drv vimc_sen_cfs_drv = {
+	.name = VIMC_SEN_NAME,
+	.create_pads = vimc_sen_create_cfs_pads,
+};
+
+__exit void vimc_sen_exit(void)
+{
+	vimc_cfs_drv_unregister(&vimc_sen_cfs_drv);
+}
+
+__init void vimc_sen_init(void)
+{
+	vimc_cfs_drv_register(&vimc_sen_cfs_drv);
+}
-- 
2.20.1