[PATCH 2/2] drm/vkms: Introduce configfs for enabling/disabling connectors

[Rodrigo Siqueira]

This patch introduces an implementation of vkms subsystems through
configfs; we want to be able to reconfigure vkms instance without having
to reload the module. This commit adds the primary support for configfs
by allowing vkms to expose the ability to enable/disable its connectors.

Signed-off-by: Rodrigo Siqueira <rodrigosiqueiramelo@xxxxxxxxx>
---
 drivers/gpu/drm/vkms/Makefile        |   3 +-
 drivers/gpu/drm/vkms/vkms_configfs.c | 229 +++++++++++++++++++++++++++
 drivers/gpu/drm/vkms/vkms_drv.c      |   6 +
 drivers/gpu/drm/vkms/vkms_drv.h      |  12 ++
 4 files changed, 249 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/vkms/vkms_configfs.c

diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
index 333d3cead0e3..f90c016cd9fe 100644
--- a/drivers/gpu/drm/vkms/Makefile
+++ b/drivers/gpu/drm/vkms/Makefile
@@ -6,6 +6,7 @@ vkms-y := \
 	vkms_crtc.o \
 	vkms_gem.o \
 	vkms_composer.o \
-	vkms_writeback.o
+	vkms_writeback.o \
+	vkms_configfs.o
 
 obj-$(CONFIG_DRM_VKMS) += vkms.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..5d1a30517cca
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -0,0 +1,229 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include "vkms_drv.h"
+
+static struct config_group *connector_group;
+static struct vkms_device *vkms_device;
+
+static char *available_connectors[] = {
+	"Virtual",
+	"Writeback",
+};
+
+struct connectors_fs {
+	struct config_item item;
+	bool enable;
+};
+
+static int enable_connector(const char *name)
+{
+	int ret = 0;
+
+	if (!strcmp(name, "Writeback"))
+		ret = enable_writeback_connector(vkms_device);
+	else if (!strcmp(name, "Virtual"))
+		ret = enable_virtual_connector(vkms_device);
+
+	if (ret)
+		return ret;
+
+	drm_mode_config_reset(&vkms_device->drm);
+	return 0;
+}
+
+static void disable_connector(const char *name)
+{
+	if (!strcmp(name, "Writeback"))
+		disable_writeback_connector(vkms_device);
+	else if (!strcmp(name, "Virtual"))
+		disable_virtual_connector(vkms_device);
+}
+
+static inline struct connectors_fs *to_conn_item(struct config_item *item)
+{
+	return item ? container_of(item, struct connectors_fs, item) : NULL;
+}
+
+static ssize_t conn_fs_enable_show(struct config_item *item, char *page)
+{
+	struct connectors_fs *conn_item = to_conn_item(item);
+
+	return sprintf(page, "%d\n", conn_item->enable);
+}
+
+static ssize_t conn_fs_enable_store(struct config_item *item,
+				    const char *page, size_t count)
+{
+	struct connectors_fs *conn_item = to_conn_item(item);
+	char *p = (char *)page;
+	unsigned int enable;
+	int ret;
+
+	ret = kstrtouint(p, 10, &enable);
+	if (ret)
+		return -EINVAL;
+
+	if (enable > 1)
+		return -EINVAL;
+
+	if (enable == conn_item->enable)
+		return count;
+
+	if (enable) {
+		ret = enable_connector(item->ci_name);
+		if (ret)
+			return ret;
+	} else {
+		disable_connector(item->ci_name);
+	}
+
+	conn_item->enable = enable ? true : false;
+	return count;
+}
+
+CONFIGFS_ATTR(conn_fs_, enable);
+
+static struct configfs_attribute *connectors_fs_attrs[] = {
+	&conn_fs_attr_enable,
+	NULL,
+};
+
+static void connectors_fs_release(struct config_item *item)
+{
+	kfree(to_conn_item(item));
+}
+
+static struct configfs_item_operations connectors_fs_ops = {
+	.release = connectors_fs_release,
+};
+
+static const struct config_item_type connectors_fs_type = {
+	.ct_item_ops	= &connectors_fs_ops,
+	.ct_attrs	= connectors_fs_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct config_item *make_connector_item(struct config_group *group,
+					       const char *name)
+{
+	struct connectors_fs *conn_item;
+	int i, ret, total_conn = ARRAY_SIZE(available_connectors);
+
+	for (i = 0; i < total_conn; i++)
+		if (!strcmp(name, available_connectors[i]))
+			break;
+
+	if (i == total_conn)
+		return ERR_PTR(-EINVAL);
+
+	ret = enable_connector(name);
+	if (ret)
+		return ERR_PTR(ret);
+
+	conn_item = kzalloc(sizeof(*conn_item), GFP_KERNEL);
+	if (!conn_item)
+		return ERR_PTR(-ENOMEM);
+
+	config_item_init_type_name(&conn_item->item, name,
+				   &connectors_fs_type);
+
+	conn_item->enable = true;
+
+	return &conn_item->item;
+}
+
+static void drop_connector_item(struct config_group *group,
+				struct config_item *item)
+{
+	char *name = item->ci_name;
+
+	disable_connector(name);
+
+	config_item_put(item);
+}
+
+static struct configfs_group_operations connector_group_ops = {
+	.make_item	= make_connector_item,
+	.drop_item	= drop_connector_item,
+};
+
+static const struct config_item_type connector_type = {
+	.ct_group_ops	= &connector_group_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+static const struct config_item_type vkms_subsystem_type = {
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct configfs_subsystem vkms_subsystem = {
+	.su_group = {
+		.cg_item = {
+			.ci_namebuf = "vkms",
+			.ci_type = &vkms_subsystem_type,
+		},
+	},
+	.su_mutex = __MUTEX_INITIALIZER(vkms_subsystem.su_mutex),
+};
+
+static void init_default_conn_configfs(struct config_group *root)
+{
+	struct vkms_config_state *config_state = &vkms_device->config_state;
+	int i, ret;
+
+	connector_group = configfs_register_default_group(root, "connectors",
+							  &connector_type);
+	if (IS_ERR(connector_group)) {
+		ret = PTR_ERR(connector_group);
+		pr_err("Error %d while registering functions group\n", ret);
+		return;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(available_connectors); i++) {
+		struct config_group *group = config_state->connectors[i];
+
+		if (!strcmp(available_connectors[i], "Writeback") &&
+		    !enable_writeback)
+			continue;
+
+		group = configfs_register_default_group(connector_group,
+							available_connectors[i],
+							&connectors_fs_type);
+		if (IS_ERR(connector_group)) {
+			ret = PTR_ERR(config_state->connectors[i]);
+			DRM_ERROR("Error %d while trying to register %s\n",
+				  ret, available_connectors[i]);
+			continue;
+		}
+
+		to_conn_item(&group->cg_item)->enable = true;
+	}
+}
+
+int vkms_configfs_init(struct vkms_device *vkmsdev)
+{
+	struct config_group *root = &vkms_subsystem.su_group;
+	int ret;
+
+	vkms_device = vkmsdev;
+
+	config_group_init(root);
+	ret = configfs_register_subsystem(&vkms_subsystem);
+	if (ret) {
+		pr_err("Error %d while registering subsystem %s\n", ret,
+		       root->cg_item.ci_namebuf);
+		goto err;
+	}
+
+	init_default_conn_configfs(root);
+
+	return 0;
+
+err:
+	return ret;
+}
+
+void vkms_configfs_exit(void)
+{
+	configfs_unregister_subsystem(&vkms_subsystem);
+}
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index 152d7de24a76..a930a5a52ce4 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -166,6 +166,10 @@ static int __init vkms_init(void)
 	if (ret)
 		goto out_fini;
 
+	ret = vkms_configfs_init(vkms_device);
+	if (ret)
+		DRM_ERROR("Could not initialize configfs");
+
 	ret = drm_dev_register(&vkms_device->drm, 0);
 	if (ret)
 		goto out_fini;
@@ -194,6 +198,8 @@ static void __exit vkms_exit(void)
 	drm_dev_put(&vkms_device->drm);
 
 	kfree(vkms_device);
+
+	vkms_configfs_exit();
 }
 
 module_init(vkms_init);
diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
index a1ca5c658355..c811bc192606 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.h
+++ b/drivers/gpu/drm/vkms/vkms_drv.h
@@ -9,6 +9,7 @@
 #include <drm/drm_encoder.h>
 #include <drm/drm_writeback.h>
 #include <linux/hrtimer.h>
+#include <linux/configfs.h>
 
 #define XRES_MIN    20
 #define YRES_MIN    20
@@ -83,10 +84,17 @@ struct vkms_output {
 	spinlock_t composer_lock;
 };
 
+#define MAX_CONN_CONFIGFS 10
+
+struct vkms_config_state {
+	struct config_group *connectors[MAX_CONN_CONFIGFS];
+};
+
 struct vkms_device {
 	struct drm_device drm;
 	struct platform_device *platform;
 	struct vkms_output output;
+	struct vkms_config_state config_state;
 };
 
 struct vkms_gem_object {
@@ -160,4 +168,8 @@ void disable_virtual_connector(struct vkms_device *vkmsdev);
 int enable_writeback_connector(struct vkms_device *vkmsdev);
 void disable_writeback_connector(struct vkms_device *connector);
 
+/* Configfs */
+int vkms_configfs_init(struct vkms_device *vkmsdev);
+void vkms_configfs_exit(void);
+
 #endif /* _VKMS_DRV_H_ */
-- 
2.21.0