vfio/mdev: consolidate all the device_api sysfs into the core code

Every driver just emits a static string, simply feed it through the ops
and provide a standard sysfs show function.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Tony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Eric Farman <farman@linux.ibm.com>
Link: https://lore.kernel.org/r/20220923092652.100656-11-hch@lst.de
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

Documentation/driver-api/vfio-mediated-device.rst

@@ -202,7 +202,7 @@ Directories and files under the sysfs for Each Physical Device
 
 * device_api
 
-  This attribute should show which device API is being created, for example,
+  This attribute shows which device API is being created, for example,
   "vfio-pci" for a PCI device.
 
 * available_instances

drivers/gpu/drm/i915/gvt/kvmgt.c

@@ -123,12 +123,6 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
 	return sprintf(buf, "%u\n", type->avail_instance);
 }
 
-static ssize_t device_api_show(struct mdev_type *mtype,
-			       struct mdev_type_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%s\n", VFIO_DEVICE_API_PCI_STRING);
-}
-
 static ssize_t description_show(struct mdev_type *mtype,
 				struct mdev_type_attribute *attr, char *buf)
 {
@@ -151,13 +145,11 @@ static ssize_t name_show(struct mdev_type *mtype,
 }
 
 static MDEV_TYPE_ATTR_RO(available_instances);
-static MDEV_TYPE_ATTR_RO(device_api);
 static MDEV_TYPE_ATTR_RO(description);
 static MDEV_TYPE_ATTR_RO(name);
 
 static const struct attribute *gvt_type_attrs[] = {
 	&mdev_type_attr_available_instances.attr,
-	&mdev_type_attr_device_api.attr,
 	&mdev_type_attr_description.attr,
 	&mdev_type_attr_name.attr,
 	NULL,
@@ -1550,6 +1542,7 @@ static void intel_vgpu_remove(struct mdev_device *mdev)
 }
 
 static struct mdev_driver intel_vgpu_mdev_driver = {
+	.device_api	= VFIO_DEVICE_API_PCI_STRING,
 	.driver = {
 		.name		= "intel_vgpu_mdev",
 		.owner		= THIS_MODULE,

drivers/s390/cio/vfio_ccw_ops.c

@@ -51,13 +51,6 @@ static ssize_t name_show(struct mdev_type *mtype,
 }
 static MDEV_TYPE_ATTR_RO(name);
 
-static ssize_t device_api_show(struct mdev_type *mtype,
-			       struct mdev_type_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%s\n", VFIO_DEVICE_API_CCW_STRING);
-}
-static MDEV_TYPE_ATTR_RO(device_api);
-
 static ssize_t available_instances_show(struct mdev_type *mtype,
 					struct mdev_type_attribute *attr,
 					char *buf)
@@ -70,7 +63,6 @@ static MDEV_TYPE_ATTR_RO(available_instances);
 
 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,
 };
@@ -628,6 +620,7 @@ static const struct vfio_device_ops vfio_ccw_dev_ops = {
 };
 
 struct mdev_driver vfio_ccw_mdev_driver = {
+	.device_api = VFIO_DEVICE_API_CCW_STRING,
 	.driver = {
 		.name = "vfio_ccw_mdev",
 		.owner = THIS_MODULE,

drivers/s390/crypto/vfio_ap_ops.c

@@ -808,17 +808,8 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
 
 static MDEV_TYPE_ATTR_RO(available_instances);
 
-static ssize_t device_api_show(struct mdev_type *mtype,
-			       struct mdev_type_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%s\n", VFIO_DEVICE_API_AP_STRING);
-}
-
-static MDEV_TYPE_ATTR_RO(device_api);
-
 static const struct attribute *vfio_ap_mdev_type_attrs[] = {
 	&mdev_type_attr_name.attr,
-	&mdev_type_attr_device_api.attr,
 	&mdev_type_attr_available_instances.attr,
 	NULL,
 };
@@ -1799,6 +1790,7 @@ static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
 };
 
 static struct mdev_driver vfio_ap_matrix_driver = {
+	.device_api = VFIO_DEVICE_API_AP_STRING,
 	.driver = {
 		.name = "vfio_ap_mdev",
 		.owner = THIS_MODULE,

drivers/vfio/mdev/mdev_driver.c

@@ -55,8 +55,10 @@ struct bus_type mdev_bus_type = {
  **/
 int mdev_register_driver(struct mdev_driver *drv)
 {
-	if (!drv->types_attrs)
+	if (!drv->types_attrs || !drv->device_api)
 		return -EINVAL;
+
+	/* initialize common driver fields */
 	drv->driver.bus = &mdev_bus_type;
 	return driver_register(&drv->driver);
 }

drivers/vfio/mdev/mdev_sysfs.c

@@ -72,9 +72,30 @@ static ssize_t create_store(struct mdev_type *mtype,
 
 	return count;
 }
-
 static MDEV_TYPE_ATTR_WO(create);
 
+static ssize_t device_api_show(struct mdev_type *mtype,
+			       struct mdev_type_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%s\n", mtype->parent->mdev_driver->device_api);
+}
+static MDEV_TYPE_ATTR_RO(device_api);
+
+static struct attribute *mdev_types_core_attrs[] = {
+	&mdev_type_attr_create.attr,
+	&mdev_type_attr_device_api.attr,
+	NULL,
+};
+
+static struct attribute_group mdev_type_core_group = {
+	.attrs = mdev_types_core_attrs,
+};
+
+static const struct attribute_group *mdev_type_groups[] = {
+	&mdev_type_core_group,
+	NULL,
+};
+
 static void mdev_type_release(struct kobject *kobj)
 {
 	struct mdev_type *type = to_mdev_type(kobj);
@@ -87,6 +108,7 @@ static void mdev_type_release(struct kobject *kobj)
 static struct kobj_type mdev_type_ktype = {
 	.sysfs_ops	= &mdev_type_sysfs_ops,
 	.release	= mdev_type_release,
+	.default_groups	= mdev_type_groups,
 };
 
 static int mdev_type_add(struct mdev_parent *parent, struct mdev_type *type)
@@ -106,10 +128,6 @@ static int mdev_type_add(struct mdev_parent *parent, struct mdev_type *type)
 		return ret;
 	}
 
-	ret = sysfs_create_file(&type->kobj, &mdev_type_attr_create.attr);
-	if (ret)
-		goto attr_create_failed;
-
 	type->devices_kobj = kobject_create_and_add("devices", &type->kobj);
 	if (!type->devices_kobj) {
 		ret = -ENOMEM;
@@ -124,8 +142,6 @@ static int mdev_type_add(struct mdev_parent *parent, struct mdev_type *type)
 attrs_failed:
 	kobject_put(type->devices_kobj);
 attr_devices_failed:
-	sysfs_remove_file(&type->kobj, &mdev_type_attr_create.attr);
-attr_create_failed:
 	kobject_del(&type->kobj);
 	kobject_put(&type->kobj);
 	return ret;
@@ -136,7 +152,6 @@ static void mdev_type_remove(struct mdev_type *type)
 	sysfs_remove_files(&type->kobj, type->parent->mdev_driver->types_attrs);
 
 	kobject_put(type->devices_kobj);
-	sysfs_remove_file(&type->kobj, &mdev_type_attr_create.attr);
 	kobject_del(&type->kobj);
 	kobject_put(&type->kobj);
 }

include/linux/mdev.h

@@ -61,11 +61,6 @@ struct mdev_type_attribute {
 			 size_t count);
 };
 
-#define MDEV_TYPE_ATTR(_name, _mode, _show, _store)		\
-struct mdev_type_attribute mdev_type_attr_##_name =		\
-	__ATTR(_name, _mode, _show, _store)
-#define MDEV_TYPE_ATTR_RW(_name) \
-	struct mdev_type_attribute mdev_type_attr_##_name = __ATTR_RW(_name)
 #define MDEV_TYPE_ATTR_RO(_name) \
 	struct mdev_type_attribute mdev_type_attr_##_name = __ATTR_RO(_name)
 #define MDEV_TYPE_ATTR_WO(_name) \
@@ -73,12 +68,14 @@ struct mdev_type_attribute mdev_type_attr_##_name =		\
 
 /**
  * struct mdev_driver - Mediated device driver
+ * @device_api: string to return for the device_api sysfs
  * @probe: called when new device created
  * @remove: called when device removed
  * @types_attrs: attributes to the type kobjects.
  * @driver: device driver structure
  **/
 struct mdev_driver {
+	const char *device_api;
 	int (*probe)(struct mdev_device *dev);
 	void (*remove)(struct mdev_device *dev);
 	const struct attribute * const *types_attrs;

samples/vfio-mdev/mbochs.c

@@ -1384,17 +1384,9 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
 }
 static MDEV_TYPE_ATTR_RO(available_instances);
 
-static ssize_t device_api_show(struct mdev_type *mtype,
-			       struct mdev_type_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%s\n", VFIO_DEVICE_API_PCI_STRING);
-}
-static MDEV_TYPE_ATTR_RO(device_api);
-
 static const struct attribute *mdev_types_attrs[] = {
 	&mdev_type_attr_name.attr,
 	&mdev_type_attr_description.attr,
-	&mdev_type_attr_device_api.attr,
 	&mdev_type_attr_available_instances.attr,
 	NULL,
 };
@@ -1410,6 +1402,7 @@ static const struct vfio_device_ops mbochs_dev_ops = {
 };
 
 static struct mdev_driver mbochs_driver = {
+	.device_api = VFIO_DEVICE_API_PCI_STRING,
 	.driver = {
 		.name = "mbochs",
 		.owner = THIS_MODULE,

samples/vfio-mdev/mdpy.c

@@ -689,17 +689,9 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
 }
 static MDEV_TYPE_ATTR_RO(available_instances);
 
-static ssize_t device_api_show(struct mdev_type *mtype,
-			       struct mdev_type_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%s\n", VFIO_DEVICE_API_PCI_STRING);
-}
-static MDEV_TYPE_ATTR_RO(device_api);
-
 static const struct attribute *mdev_types_attrs[] = {
 	&mdev_type_attr_name.attr,
 	&mdev_type_attr_description.attr,
-	&mdev_type_attr_device_api.attr,
 	&mdev_type_attr_available_instances.attr,
 	NULL,
 };
@@ -714,6 +706,7 @@ static const struct vfio_device_ops mdpy_dev_ops = {
 };
 
 static struct mdev_driver mdpy_driver = {
+	.device_api = VFIO_DEVICE_API_PCI_STRING,
 	.driver = {
 		.name = "mdpy",
 		.owner = THIS_MODULE,

samples/vfio-mdev/mtty.c

@@ -1277,17 +1277,8 @@ static ssize_t available_instances_show(struct mdev_type *mtype,
 
 static MDEV_TYPE_ATTR_RO(available_instances);
 
-static ssize_t device_api_show(struct mdev_type *mtype,
-			       struct mdev_type_attribute *attr, char *buf)
-{
-	return sprintf(buf, "%s\n", VFIO_DEVICE_API_PCI_STRING);
-}
-
-static MDEV_TYPE_ATTR_RO(device_api);
-
 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,
 };
@@ -1302,6 +1293,7 @@ static const struct vfio_device_ops mtty_dev_ops = {
 };
 
 static struct mdev_driver mtty_driver = {
+	.device_api = VFIO_DEVICE_API_PCI_STRING,
 	.driver = {
 		.name = "mtty",
 		.owner = THIS_MODULE,