[PATCH RFC v2 03/16] drm/vkms: Introduce ConfigFS interface

[Louis Chauvet <louis.chauvet@bootlin.com>]

VKMS is manly used to test userspace program and its behavior. The current
implementation is not very configurable as you can only have one device,
with few specific planes.

This is the introduction of a basic interface to dynamically create new
devices.

The new interface is:
/config/vkms
  DEVICE_1
  ┗━ enable
  DEVICE_2
  ┗━ enable

Signed-off-by: Louis Chauvet <louis.chauvet@bootlin.com>
---
 drivers/gpu/drm/vkms/Kconfig         |   1 +
 drivers/gpu/drm/vkms/Makefile        |   1 +
 drivers/gpu/drm/vkms/vkms_configfs.c | 144 +++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/vkms/vkms_configfs.h |  35 +++++++++
 drivers/gpu/drm/vkms/vkms_drv.c      |  15 +++-
 5 files changed, 194 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/vkms/Kconfig b/drivers/gpu/drm/vkms/Kconfig
index d4665e913de7702fbd5c0f047876dad9715c690a..71fe9124bf18dd5b17b0989077e1cf1f8f1ee963 100644
--- a/drivers/gpu/drm/vkms/Kconfig
+++ b/drivers/gpu/drm/vkms/Kconfig
@@ -6,6 +6,7 @@ config DRM_VKMS
 	select DRM_CLIENT_SELECTION
 	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 2b6db5870b977f6e5013982af89a48aec6c11983..9ecf6bc4779f81cac2677a3595c0bf4ebd1448bd 100644
--- a/drivers/gpu/drm/vkms/Makefile
+++ b/drivers/gpu/drm/vkms/Makefile
@@ -1,5 +1,6 @@
 # SPDX-License-Identifier: GPL-2.0-only
 vkms-y := \
+	vkms_configfs.o \
 	vkms_drv.o \
 	vkms_plane.o \
 	vkms_output.o \
diff --git a/drivers/gpu/drm/vkms/vkms_configfs.c b/drivers/gpu/drm/vkms/vkms_configfs.c
new file mode 100644
index 0000000000000000000000000000000000000000..6535672f008401cf1ae008ff2ef74452b2575eab
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_configfs.c
@@ -0,0 +1,144 @@
+// SPDX-License-Identifier: GPL-2.0+
+
+#include <linux/configfs.h>
+#include <linux/mutex.h>
+#include <drm/drm_print.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+#include "vkms_configfs.h"
+#include "vkms_drv.h"
+#include "vkms_config.h"
+
+static ssize_t device_enable_show(struct config_item *item, char *page)
+{
+	return sprintf(page, "%d\n",
+		       config_item_to_vkms_configfs_device(item)->enabled);
+}
+
+static ssize_t device_enable_store(struct config_item *item,
+				   const char *page, size_t count)
+{
+	struct vkms_configfs_device *vkms_configfs_device =
+		config_item_to_vkms_configfs_device(item);
+
+	bool value;
+	int ret;
+
+	ret = kstrtobool(page, &value);
+	if (ret)
+		return -EINVAL;
+
+	mutex_lock(&vkms_configfs_device->lock);
+
+	vkms_configfs_device->enabled = value;
+
+	if (value)
+		vkms_create(vkms_configfs_device->vkms_config);
+	else
+		vkms_destroy(vkms_configfs_device->vkms_config);
+
+	mutex_unlock(&vkms_configfs_device->lock);
+
+	return (ssize_t)count;
+}
+
+CONFIGFS_ATTR(device_, enable);
+
+static struct configfs_attribute *device_attrs[] = {
+	&device_attr_enable,
+	NULL,
+};
+
+static void device_release(struct config_item *item)
+{
+	struct vkms_configfs_device *vkms_configfs_device =
+					    config_item_to_vkms_configfs_device(item);
+
+	mutex_destroy(&vkms_configfs_device->lock);
+	vkms_config_destroy(vkms_configfs_device->vkms_config);
+
+	kfree(vkms_configfs_device);
+}
+
+static struct configfs_item_operations device_item_operations = {
+	.release	= &device_release,
+};
+
+static const struct config_item_type device_item_type = {
+	.ct_attrs	= device_attrs,
+	.ct_item_ops	= &device_item_operations,
+	.ct_owner	= THIS_MODULE,
+};
+
+/* Top directory management. Each new directory here is a new device */
+static struct config_group *root_make_group(struct config_group *group,
+					    const char *name)
+{
+	struct vkms_config_plane *plane;
+	struct vkms_config_crtc *crtc;
+	struct vkms_config_encoder *encoder;
+	struct vkms_configfs_device *configfs = kzalloc(sizeof(*configfs), GFP_KERNEL);
+
+	if (!configfs)
+		return ERR_PTR(-ENOMEM);
+
+	mutex_init(&configfs->lock);
+
+	configfs->vkms_config = vkms_config_create();
+
+	if (!configfs->vkms_config) {
+		kfree(configfs);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	plane = vkms_config_create_plane(configfs->vkms_config);
+	crtc = vkms_config_create_crtc(configfs->vkms_config);
+	encoder = vkms_config_create_encoder(configfs->vkms_config);
+
+	if (!plane || !crtc || !encoder ||
+	    vkms_config_plane_attach_crtc(plane, crtc) ||
+	    vkms_config_encoder_attach_crtc(encoder, crtc)) {
+		vkms_config_destroy(configfs->vkms_config);
+		kfree(configfs);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	plane->type = DRM_PLANE_TYPE_PRIMARY;
+
+	config_group_init_type_name(&configfs->group, name,
+				    &device_item_type);
+
+	return &configfs->group;
+}
+
+static struct configfs_group_operations root_group_operations = {
+	.make_group	= &root_make_group,
+};
+
+static struct config_item_type root_item_type = {
+	.ct_group_ops	= &root_group_operations,
+	.ct_owner	= THIS_MODULE,
+};
+
+static struct configfs_subsystem vkms_subsys = {
+	.su_group = {
+		.cg_item = {
+			.ci_name = "vkms",
+			.ci_type = &root_item_type,
+		},
+	},
+	.su_mutex = __MUTEX_INITIALIZER(vkms_subsys.su_mutex),
+};
+
+int vkms_init_configfs(void)
+{
+	config_group_init(&vkms_subsys.su_group);
+
+	return configfs_register_subsystem(&vkms_subsys);
+}
+
+void vkms_unregister_configfs(void)
+{
+	configfs_unregister_subsystem(&vkms_subsys);
+}
diff --git a/drivers/gpu/drm/vkms/vkms_configfs.h b/drivers/gpu/drm/vkms/vkms_configfs.h
new file mode 100644
index 0000000000000000000000000000000000000000..3de89c9c552c6603396f38a98ad35263f04bce26
--- /dev/null
+++ b/drivers/gpu/drm/vkms/vkms_configfs.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+
+#include <linux/configfs.h>
+#include <linux/mutex.h>
+
+#ifndef _VKMS_CONFIGFS_H
+#define _VKMS_CONFIGFS_H
+
+/**
+ * struct vkms_configfs_device - Internal object to manage all the configfs items related to one
+ * device
+ *
+ * @group: Main configfs group for a device
+ * @platform_device: If a device was created (@enabled = true), stores a pointer to it
+ * @lock: Mutex used to avoid conflicting edition of @vkms_config
+ * @enabled: Store if the device was created or not
+ * @vkms_config: Current vkms configuration
+ */
+struct vkms_configfs_device {
+	struct config_group group;
+
+	struct mutex lock;
+	bool enabled;
+
+	struct vkms_config *vkms_config;
+};
+
+#define config_item_to_vkms_configfs_device(item) \
+	container_of(to_config_group((item)), struct vkms_configfs_device, group)
+
+/* ConfigFS Support */
+int vkms_init_configfs(void);
+void vkms_unregister_configfs(void);
+
+#endif /* _VKMS_CONFIGFS_H */
diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
index 8ffbd5fc65350ba03f870726b669d189f62bad6f..cdf51df78802cd096b71cfc76678a9ebdd06df1a 100644
--- a/drivers/gpu/drm/vkms/vkms_drv.c
+++ b/drivers/gpu/drm/vkms/vkms_drv.c
@@ -29,6 +29,7 @@
 
 #include "vkms_drv.h"
 #include "vkms_config.h"
+#include "vkms_configfs.h"
 
 #include <drm/drm_print.h>
 #include <drm/drm_debugfs.h>
@@ -158,7 +159,7 @@ int vkms_create(struct vkms_config *config)
 	struct platform_device *pdev;
 	struct vkms_device *vkms_device;
 
-	pdev = platform_device_register_simple(DRIVER_NAME, -1, NULL, 0);
+	pdev = platform_device_register_simple(DRIVER_NAME, PLATFORM_DEVID_AUTO, NULL, 0);
 	if (IS_ERR(pdev))
 		return PTR_ERR(pdev);
 
@@ -219,9 +220,17 @@ static int __init vkms_init(void)
 	if (IS_ERR(default_config))
 		return PTR_ERR(default_config);
 
+	ret = vkms_init_configfs();
+	if (ret) {
+		DRM_ERROR("Unable to initialize configfs\n");
+		vkms_config_destroy(default_config);
+	}
+
 	ret = vkms_create(default_config);
-	if (ret)
+	if (ret) {
+		vkms_unregister_configfs();
 		vkms_config_destroy(default_config);
+	}
 
 	return ret;
 }
@@ -251,6 +260,8 @@ static void __exit vkms_exit(void)
 		vkms_destroy(default_config);
 
 	vkms_config_destroy(default_config);
+
+	vkms_unregister_configfs();
 }
 
 module_init(vkms_init);

-- 
2.47.0