Re: [PATCH 3/8] vfio/mdev: simplify mdev_type handling

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<snip...>

  static ssize_t remove_store(struct device *dev, struct device_attribute *attr,
  			    const char *buf, size_t count)
diff --git a/include/linux/mdev.h b/include/linux/mdev.h
index 327ce3e5c6b5f..cbb53dcd20d9d 100644
--- a/include/linux/mdev.h
+++ b/include/linux/mdev.h
@@ -23,12 +23,17 @@ struct mdev_device {
  	bool active;
  };
+struct mdev_type {
+	struct kobject kobj;
+	struct kobject *devices_kobj;
+	struct mdev_parent *parent;
+};
+
  /* embedded into the struct device that the mdev devices hang off */
  struct mdev_parent {
  	struct device *dev;
  	struct mdev_driver *mdev_driver;
  	struct kset *mdev_types_kset;
-	struct list_head type_list;
  	/* Synchronize device creation/removal with parent unregistration */
  	struct rw_semaphore unreg_sem;
  };
@@ -38,8 +43,11 @@ static inline struct mdev_device *to_mdev_device(struct device *dev)
  	return container_of(dev, struct mdev_device, dev);
  }
-unsigned int mdev_get_type_group_id(struct mdev_device *mdev);
-unsigned int mtype_get_type_group_id(struct mdev_type *mtype);
+int mdev_type_add(struct mdev_parent *parent, struct mdev_type *type,
+		const char *name, const struct attribute * const *attrs);
+void mdev_type_remove(struct mdev_type *type,
+		const struct attribute * const *attrs);
+
  struct device *mtype_get_parent_dev(struct mdev_type *mtype);
/* interface for exporting mdev supported type attributes */
@@ -66,15 +74,12 @@ struct mdev_type_attribute mdev_type_attr_##_name =		\
   * struct mdev_driver - Mediated device driver
   * @probe: called when new device created
   * @remove: called when device removed
- * @supported_type_groups: Attributes to define supported types. It is mandatory
- *			to provide supported types.
   * @driver: device driver structure
   *
   **/
  struct mdev_driver {
  	int (*probe)(struct mdev_device *dev);
  	void (*remove)(struct mdev_device *dev);
-	struct attribute_group **supported_type_groups;
  	struct device_driver driver;
  };

mdev_type should be part of mdev_parent, separating it from mdev_parent could result in more errors while using mdev framework. Similarly it should be added as part of mdev_register_device. Below adding types is separated from mdev_register_device which is more error prone. What if driver registering to mdev doesn't add mdev_types? - mdev framework is un-usable in that case. We had kept it together with mdev registration so that mdev_types should be mandatory to be defined by driver during registration. How would you mandate mdev_type by such separation?

Thanks,
Kirti


diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c
index f0967a81eabe7..32fd6f385fafd 100644
--- a/samples/vfio-mdev/mbochs.c
+++ b/samples/vfio-mdev/mbochs.c
@@ -100,23 +100,28 @@ MODULE_PARM_DESC(mem, "megabytes available to " MBOCHS_NAME " devices");
  #define MBOCHS_TYPE_2 "medium"
  #define MBOCHS_TYPE_3 "large"
-static const struct mbochs_type {
+static struct mbochs_type {
+	struct mdev_type type;
+	const char *fname;
  	const char *name;
  	u32 mbytes;
  	u32 max_x;
  	u32 max_y;
  } mbochs_types[] = {
  	{
+		.fname	= MBOCHS_TYPE_1,
  		.name	= MBOCHS_CLASS_NAME "-" MBOCHS_TYPE_1,
  		.mbytes = 4,
  		.max_x  = 800,
  		.max_y  = 600,
  	}, {
+		.fname	= MBOCHS_TYPE_2,
  		.name	= MBOCHS_CLASS_NAME "-" MBOCHS_TYPE_2,
  		.mbytes = 16,
  		.max_x  = 1920,
  		.max_y  = 1440,
  	}, {
+		.fname	= MBOCHS_TYPE_3,
  		.name	= MBOCHS_CLASS_NAME "-" MBOCHS_TYPE_3,
  		.mbytes = 64,
  		.max_x  = 0,
@@ -509,8 +514,8 @@ static int mbochs_reset(struct mdev_state *mdev_state)
  static int mbochs_probe(struct mdev_device *mdev)
  {
  	int avail_mbytes = atomic_read(&mbochs_avail_mbytes);
-	const struct mbochs_type *type =
-		&mbochs_types[mdev_get_type_group_id(mdev)];
+	struct mbochs_type *type =
+		container_of(mdev->type, struct mbochs_type, type);
  	struct device *dev = mdev_dev(mdev);
  	struct mdev_state *mdev_state;
  	int ret = -ENOMEM;
@@ -1329,8 +1334,8 @@ static const struct attribute_group *mdev_dev_groups[] = {
  static ssize_t name_show(struct mdev_type *mtype,
  			 struct mdev_type_attribute *attr, char *buf)
  {
-	const struct mbochs_type *type =
-		&mbochs_types[mtype_get_type_group_id(mtype)];
+	struct mbochs_type *type =
+		container_of(mtype, struct mbochs_type, type);
return sprintf(buf, "%s\n", type->name);
  }
@@ -1339,8 +1344,8 @@ static MDEV_TYPE_ATTR_RO(name);
  static ssize_t description_show(struct mdev_type *mtype,
  				struct mdev_type_attribute *attr, char *buf)
  {
-	const struct mbochs_type *type =
-		&mbochs_types[mtype_get_type_group_id(mtype)];
+	struct mbochs_type *type =
+		container_of(mtype, struct mbochs_type, type);
return sprintf(buf, "virtual display, %d MB video memory\n",
  		       type ? type->mbytes  : 0);
@@ -1351,8 +1356,8 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
  					struct mdev_type_attribute *attr,
  					char *buf)
  {
-	const struct mbochs_type *type =
-		&mbochs_types[mtype_get_type_group_id(mtype)];
+	struct mbochs_type *type =
+		container_of(mtype, struct mbochs_type, type);
  	int count = atomic_read(&mbochs_avail_mbytes) / type->mbytes;
return sprintf(buf, "%d\n", count);
@@ -1366,7 +1371,7 @@ static ssize_t device_api_show(struct mdev_type *mtype,
  }
  static MDEV_TYPE_ATTR_RO(device_api);
-static struct attribute *mdev_types_attrs[] = {
+static const struct attribute *mdev_types_attrs[] = {
  	&mdev_type_attr_name.attr,
  	&mdev_type_attr_description.attr,
  	&mdev_type_attr_device_api.attr,
@@ -1374,28 +1379,6 @@ static struct attribute *mdev_types_attrs[] = {
  	NULL,
  };
-static struct attribute_group mdev_type_group1 = {
-	.name  = MBOCHS_TYPE_1,
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group mdev_type_group2 = {
-	.name  = MBOCHS_TYPE_2,
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group mdev_type_group3 = {
-	.name  = MBOCHS_TYPE_3,
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group *mdev_type_groups[] = {
-	&mdev_type_group1,
-	&mdev_type_group2,
-	&mdev_type_group3,
-	NULL,
-};
-
  static const struct vfio_device_ops mbochs_dev_ops = {
  	.close_device = mbochs_close_device,
  	.read = mbochs_read,
@@ -1413,7 +1396,6 @@ static struct mdev_driver mbochs_driver = {
  	},
  	.probe = mbochs_probe,
  	.remove	= mbochs_remove,
-	.supported_type_groups = mdev_type_groups,
  };
static const struct file_operations vd_fops = {
@@ -1427,7 +1409,7 @@ static void mbochs_device_release(struct device *dev)
static int __init mbochs_dev_init(void)
  {
-	int ret = 0;
+	int i, ret = 0;
atomic_set(&mbochs_avail_mbytes, max_mbytes); @@ -1461,9 +1443,19 @@ static int __init mbochs_dev_init(void)
  	ret = mdev_register_parent(&mbochs_parent, &mbochs_dev, &mbochs_driver);
  	if (ret)
  		goto err_device;
+	for (i = 0; i < ARRAY_SIZE(mbochs_types); i++) {
+		ret = mdev_type_add(&mbochs_parent, &mbochs_types[i].type,
+				    mbochs_types[i].fname, mdev_types_attrs);
+		if (ret)
+			goto err_types;
+	}
return 0; +err_types:
+	while (--i >= 0)
+		mdev_type_remove(&mbochs_types[i].type, mdev_types_attrs);
+	mdev_unregister_parent(&mbochs_parent);
  err_device:
  	device_unregister(&mbochs_dev);
  err_class:
@@ -1478,7 +1470,11 @@ static int __init mbochs_dev_init(void)
static void __exit mbochs_dev_exit(void)
  {
+	int i;
+
  	mbochs_dev.bus = NULL;
+	for (i = 0; i < ARRAY_SIZE(mbochs_types); i++)
+		mdev_type_remove(&mbochs_types[i].type, mdev_types_attrs);
  	mdev_unregister_parent(&mbochs_parent);
device_unregister(&mbochs_dev);
diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c
index 8ab88a1d149cb..a6aa7f6f97095 100644
--- a/samples/vfio-mdev/mdpy.c
+++ b/samples/vfio-mdev/mdpy.c
@@ -52,7 +52,9 @@ MODULE_PARM_DESC(count, "number of " MDPY_NAME " devices");
  #define MDPY_TYPE_2 "xga"
  #define MDPY_TYPE_3 "hd"
-static const struct mdpy_type {
+static struct mdpy_type {
+	struct mdev_type type;
+	const char *fname;
  	const char *name;
  	u32 format;
  	u32 bytepp;
@@ -60,18 +62,21 @@ static const struct mdpy_type {
  	u32 height;
  } mdpy_types[] = {
  	{
+		.fname 	= MDPY_TYPE_1,
  		.name	= MDPY_CLASS_NAME "-" MDPY_TYPE_1,
  		.format = DRM_FORMAT_XRGB8888,
  		.bytepp = 4,
  		.width	= 640,
  		.height = 480,
  	}, {
+		.fname 	= MDPY_TYPE_2,
  		.name	= MDPY_CLASS_NAME "-" MDPY_TYPE_2,
  		.format = DRM_FORMAT_XRGB8888,
  		.bytepp = 4,
  		.width	= 1024,
  		.height = 768,
  	}, {
+		.fname 	= MDPY_TYPE_3,
  		.name	= MDPY_CLASS_NAME "-" MDPY_TYPE_3,
  		.format = DRM_FORMAT_XRGB8888,
  		.bytepp = 4,
@@ -220,7 +225,7 @@ static int mdpy_reset(struct mdev_state *mdev_state)
  static int mdpy_probe(struct mdev_device *mdev)
  {
  	const struct mdpy_type *type =
-		&mdpy_types[mdev_get_type_group_id(mdev)];
+		container_of(mdev->type, struct mdpy_type, type);
  	struct device *dev = mdev_dev(mdev);
  	struct mdev_state *mdev_state;
  	u32 fbsize;
@@ -645,8 +650,7 @@ static const struct attribute_group *mdev_dev_groups[] = {
  static ssize_t name_show(struct mdev_type *mtype,
  			 struct mdev_type_attribute *attr, char *buf)
  {
-	const struct mdpy_type *type =
-		&mdpy_types[mtype_get_type_group_id(mtype)];
+	struct mdpy_type *type = container_of(mtype, struct mdpy_type, type);
return sprintf(buf, "%s\n", type->name);
  }
@@ -655,8 +659,7 @@ static MDEV_TYPE_ATTR_RO(name);
  static ssize_t description_show(struct mdev_type *mtype,
  				struct mdev_type_attribute *attr, char *buf)
  {
-	const struct mdpy_type *type =
-		&mdpy_types[mtype_get_type_group_id(mtype)];
+	struct mdpy_type *type = container_of(mtype, struct mdpy_type, type);
return sprintf(buf, "virtual display, %dx%d framebuffer\n",
  		       type->width, type->height);
@@ -678,7 +681,7 @@ static ssize_t device_api_show(struct mdev_type *mtype,
  }
  static MDEV_TYPE_ATTR_RO(device_api);
-static struct attribute *mdev_types_attrs[] = {
+static const struct attribute *mdev_types_attrs[] = {
  	&mdev_type_attr_name.attr,
  	&mdev_type_attr_description.attr,
  	&mdev_type_attr_device_api.attr,
@@ -686,28 +689,6 @@ static struct attribute *mdev_types_attrs[] = {
  	NULL,
  };
-static struct attribute_group mdev_type_group1 = {
-	.name  = MDPY_TYPE_1,
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group mdev_type_group2 = {
-	.name  = MDPY_TYPE_2,
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group mdev_type_group3 = {
-	.name  = MDPY_TYPE_3,
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group *mdev_type_groups[] = {
-	&mdev_type_group1,
-	&mdev_type_group2,
-	&mdev_type_group3,
-	NULL,
-};
-
  static const struct vfio_device_ops mdpy_dev_ops = {
  	.read = mdpy_read,
  	.write = mdpy_write,
@@ -724,7 +705,6 @@ static struct mdev_driver mdpy_driver = {
  	},
  	.probe = mdpy_probe,
  	.remove	= mdpy_remove,
-	.supported_type_groups = mdev_type_groups,
  };
static const struct file_operations vd_fops = {
@@ -738,7 +718,7 @@ static void mdpy_device_release(struct device *dev)
static int __init mdpy_dev_init(void)
  {
-	int ret = 0;
+	int i, ret = 0;
ret = alloc_chrdev_region(&mdpy_devt, 0, MINORMASK + 1, MDPY_NAME);
  	if (ret < 0) {
@@ -770,9 +750,19 @@ static int __init mdpy_dev_init(void)
  	ret = mdev_register_parent(&mdpy_parent, &mdpy_dev, &mdpy_driver);
  	if (ret)
  		goto err_device;
+	for (i = 0; i < ARRAY_SIZE(mdpy_types); i++) {
+		ret = mdev_type_add(&mdpy_parent, &mdpy_types[i].type,
+				    mdpy_types[i].fname, mdev_types_attrs);
+		if (ret)
+			goto err_types;
+	}
return 0; +err_types:
+	while (--i >= 0)
+		mdev_type_remove(&mdpy_types[i].type, mdev_types_attrs);
+	mdev_unregister_parent(&mdpy_parent);
  err_device:
  	device_unregister(&mdpy_dev);
  err_class:
@@ -787,7 +777,11 @@ static int __init mdpy_dev_init(void)
static void __exit mdpy_dev_exit(void)
  {
+	int i;
+
  	mdpy_dev.bus = NULL;
+	for (i = 0; i < ARRAY_SIZE(mdpy_types); i++)
+		mdev_type_remove(&mdpy_types[i].type, mdev_types_attrs);
  	mdev_unregister_parent(&mdpy_parent);
device_unregister(&mdpy_dev);
diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c
index 20136def93fdb..28c0811cf2312 100644
--- a/samples/vfio-mdev/mtty.c
+++ b/samples/vfio-mdev/mtty.c
@@ -145,6 +145,16 @@ struct mdev_state {
  	int nr_ports;
  };
+static struct mtty_type {
+	struct mdev_type type;
+	int nr_ports;
+	const char *fname;
+	const char *name;
+} mtty_types[2] = {
+	{ .nr_ports = 1, .fname = "1", .name = "Single port serial" },
+	{ .nr_ports = 2, .fname = "2", .name = "Dual port serial" },
+};
+
  static atomic_t mdev_avail_ports = ATOMIC_INIT(MAX_MTTYS);
static const struct file_operations vd_fops = {
@@ -706,16 +716,18 @@ static ssize_t mdev_access(struct mdev_state *mdev_state, u8 *buf, size_t count,
static int mtty_probe(struct mdev_device *mdev)
  {
+	struct mtty_type *type =
+		container_of(mdev->type, struct mtty_type, type);
  	struct mdev_state *mdev_state;
-	int nr_ports = mdev_get_type_group_id(mdev) + 1;
  	int avail_ports = atomic_read(&mdev_avail_ports);
  	int ret;
do {
-		if (avail_ports < nr_ports)
+		if (avail_ports < type->nr_ports)
  			return -ENOSPC;
  	} while (!atomic_try_cmpxchg(&mdev_avail_ports,
-				     &avail_ports, avail_ports - nr_ports));
+				     &avail_ports,
+				     avail_ports - type->nr_ports));
mdev_state = kzalloc(sizeof(struct mdev_state), GFP_KERNEL);
  	if (mdev_state == NULL) {
@@ -725,13 +737,13 @@ static int mtty_probe(struct mdev_device *mdev)
vfio_init_group_dev(&mdev_state->vdev, &mdev->dev, &mtty_dev_ops); - mdev_state->nr_ports = nr_ports;
+	mdev_state->nr_ports = type->nr_ports;
  	mdev_state->irq_index = -1;
  	mdev_state->s[0].max_fifo_size = MAX_FIFO_SIZE;
  	mdev_state->s[1].max_fifo_size = MAX_FIFO_SIZE;
  	mutex_init(&mdev_state->rxtx_lock);
-	mdev_state->vconfig = kzalloc(MTTY_CONFIG_SPACE_SIZE, GFP_KERNEL);
+ mdev_state->vconfig = kzalloc(MTTY_CONFIG_SPACE_SIZE, GFP_KERNEL);
  	if (mdev_state->vconfig == NULL) {
  		ret = -ENOMEM;
  		goto err_state;
@@ -754,7 +766,7 @@ static int mtty_probe(struct mdev_device *mdev)
  	vfio_uninit_group_dev(&mdev_state->vdev);
  	kfree(mdev_state);
  err_nr_ports:
-	atomic_add(nr_ports, &mdev_avail_ports);
+	atomic_add(type->nr_ports, &mdev_avail_ports);
  	return ret;
  }
@@ -1235,11 +1247,9 @@ static const struct attribute_group *mdev_dev_groups[] = {
  static ssize_t name_show(struct mdev_type *mtype,
  			 struct mdev_type_attribute *attr, char *buf)
  {
-	static const char *name_str[2] = { "Single port serial",
-					   "Dual port serial" };
+	struct mtty_type *type = container_of(mtype, struct mtty_type, type);
- return sysfs_emit(buf, "%s\n",
-			  name_str[mtype_get_type_group_id(mtype)]);
+	return sysfs_emit(buf, "%s\n", type->name);
  }
static MDEV_TYPE_ATTR_RO(name);
@@ -1248,9 +1258,10 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
  					struct mdev_type_attribute *attr,
  					char *buf)
  {
-	unsigned int ports = mtype_get_type_group_id(mtype) + 1;
+	struct mtty_type *type = container_of(mtype, struct mtty_type, type);
- return sprintf(buf, "%d\n", atomic_read(&mdev_avail_ports) / ports);
+	return sprintf(buf, "%d\n", atomic_read(&mdev_avail_ports) /
+			type->nr_ports);
  }
static MDEV_TYPE_ATTR_RO(available_instances);
@@ -1263,29 +1274,13 @@ static ssize_t device_api_show(struct mdev_type *mtype,
static MDEV_TYPE_ATTR_RO(device_api); -static struct attribute *mdev_types_attrs[] = {
+static const struct attribute *mdev_types_attrs[] = {
  	&mdev_type_attr_name.attr,
  	&mdev_type_attr_device_api.attr,
  	&mdev_type_attr_available_instances.attr,
  	NULL,
  };
-static struct attribute_group mdev_type_group1 = {
-	.name  = "1",
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group mdev_type_group2 = {
-	.name  = "2",
-	.attrs = mdev_types_attrs,
-};
-
-static struct attribute_group *mdev_type_groups[] = {
-	&mdev_type_group1,
-	&mdev_type_group2,
-	NULL,
-};
-
  static const struct vfio_device_ops mtty_dev_ops = {
  	.name = "vfio-mtty",
  	.read = mtty_read,
@@ -1302,7 +1297,6 @@ static struct mdev_driver mtty_driver = {
  	},
  	.probe = mtty_probe,
  	.remove	= mtty_remove,
-	.supported_type_groups = mdev_type_groups,
  };
static void mtty_device_release(struct device *dev)
@@ -1312,7 +1306,7 @@ static void mtty_device_release(struct device *dev)
static int __init mtty_dev_init(void)
  {
-	int ret = 0;
+	int i, ret = 0;
pr_info("mtty_dev: %s\n", __func__); @@ -1357,8 +1351,19 @@ static int __init mtty_dev_init(void)
  				   &mtty_driver);
  	if (ret)
  		goto err_device;
+	for (i = 0; i < ARRAY_SIZE(mtty_types); i++) {
+		ret = mdev_type_add(&mtty_dev.parent, &mtty_types[i].type,
+				    mtty_types[i].fname, mdev_types_attrs);
+		if (ret)
+			goto err_types;
+	}
+
  	return 0;
+err_types:
+	while (--i >= 0)
+		mdev_type_remove(&mtty_types[i].type, mdev_types_attrs);
+	mdev_unregister_parent(&mtty_dev.parent);
  err_device:
  	device_unregister(&mtty_dev.dev);
  err_class:
@@ -1373,7 +1378,11 @@ static int __init mtty_dev_init(void)
static void __exit mtty_dev_exit(void)
  {
+	int i;
+
  	mtty_dev.dev.bus = NULL;
+	for (i = 0; i < ARRAY_SIZE(mtty_types); i++)
+		mdev_type_remove(&mtty_types[i].type, mdev_types_attrs);
  	mdev_unregister_parent(&mtty_dev.parent);
device_unregister(&mtty_dev.dev);



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