[IB] uverbs: Add device-specific ABI version attribute

Add abi_version attribute to uverbs class devices to allow for
ABI versioning of device-specific interfaces.
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/core/uverbs_main.c

@@ -598,6 +598,15 @@ static ssize_t show_ibdev(struct class_device *class_dev, char *buf)
 }
 static CLASS_DEVICE_ATTR(ibdev, S_IRUGO, show_ibdev, NULL);
 
+static ssize_t show_dev_abi_version(struct class_device *class_dev, char *buf)
+{
+	struct ib_uverbs_device *dev =
+		container_of(class_dev, struct ib_uverbs_device, class_dev);
+
+	return sprintf(buf, "%d\n", dev->ib_dev->uverbs_abi_ver);
+}
+static CLASS_DEVICE_ATTR(abi_version, S_IRUGO, show_dev_abi_version, NULL);
+
 static void ib_uverbs_release_class_dev(struct class_device *class_dev)
 {
 	struct ib_uverbs_device *dev =
@@ -662,6 +671,8 @@ static void ib_uverbs_add_one(struct ib_device *device)
 
 	if (class_device_create_file(&uverbs_dev->class_dev, &class_device_attr_ibdev))
 		goto err_class;
+	if (class_device_create_file(&uverbs_dev->class_dev, &class_device_attr_abi_version))
+		goto err_class;
 
 	ib_set_client_data(device, &uverbs_client, uverbs_dev);
 

drivers/infiniband/hw/mthca/mthca_provider.c

@@ -1060,6 +1060,7 @@ int mthca_register_device(struct mthca_dev *dev)
 	strlcpy(dev->ib_dev.name, "mthca%d", IB_DEVICE_NAME_MAX);
 	dev->ib_dev.owner                = THIS_MODULE;
 
+	dev->ib_dev.uverbs_abi_ver	 = MTHCA_UVERBS_ABI_VERSION;
 	dev->ib_dev.node_type            = IB_NODE_CA;
 	dev->ib_dev.phys_port_cnt        = dev->limits.num_ports;
 	dev->ib_dev.dma_device           = &dev->pdev->dev;

drivers/infiniband/hw/mthca/mthca_user.h

@@ -37,6 +37,12 @@
 
 #include <linux/types.h>
 
+/*
+ * Increment this value if any changes that break userspace ABI
+ * compatibility are made.
+ */
+#define MTHCA_UVERBS_ABI_VERSION	1
+
 /*
  * Make sure that all structs defined in this file remain laid out so
  * that they pack the same way on 32-bit and 64-bit architectures (to

include/rdma/ib_verbs.h

@@ -951,6 +951,8 @@ struct ib_device {
 		IB_DEV_UNREGISTERED
 	}                            reg_state;
 
+	int			     uverbs_abi_ver;
+
 	u8                           node_type;
 	u8                           phys_port_cnt;
 };