[PATCH V3,net-next, 2/3] Drivers: hv: vmbus: Add dev_num to sysfs

[Haiyang Zhang <haiyangz@microsoft.com>]

It's a number based on the VMBus device offer sequence.
Useful for device naming when using Async probing.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>

---
Changes
V3:
 Use "VMBus" instead of vmbus in text.
---
 Documentation/ABI/stable/sysfs-bus-vmbus |  8 ++++++++
 drivers/hv/vmbus_drv.c                   | 13 +++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/Documentation/ABI/stable/sysfs-bus-vmbus b/Documentation/ABI/stable/sysfs-bus-vmbus
index 8e8d167..4c4dc86 100644
--- a/Documentation/ABI/stable/sysfs-bus-vmbus
+++ b/Documentation/ABI/stable/sysfs-bus-vmbus
@@ -49,6 +49,14 @@ Contact:	Stephen Hemminger <sthemmin@microsoft.com>
 Description:	This NUMA node to which the VMBUS device is
 		attached, or -1 if the node is unknown.
 
+What:           /sys/bus/vmbus/devices/<UUID>/dev_num
+Date:		Dec 2019
+KernelVersion:	5.5
+Contact:	Haiyang Zhang <haiyangz@microsoft.com>
+Description:	A number based on the VMBus device offer sequence.
+		Useful for device naming when using Async probing.
+Users:		Debugging tools and userspace drivers
+
 What:		/sys/bus/vmbus/devices/<UUID>/channels/<N>
 Date:		September. 2017
 KernelVersion:	4.14
diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c
index 4ef5a66..fe7aefa 100644
--- a/drivers/hv/vmbus_drv.c
+++ b/drivers/hv/vmbus_drv.c
@@ -214,6 +214,18 @@ static ssize_t numa_node_show(struct device *dev,
 static DEVICE_ATTR_RO(numa_node);
 #endif
 
+static ssize_t dev_num_show(struct device *dev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct hv_device *hv_dev = device_to_hv_device(dev);
+
+	if (!hv_dev->channel)
+		return -ENODEV;
+
+	return sprintf(buf, "%d\n", hv_dev->channel->dev_num);
+}
+static DEVICE_ATTR_RO(dev_num);
+
 static ssize_t server_monitor_pending_show(struct device *dev,
 					   struct device_attribute *dev_attr,
 					   char *buf)
@@ -598,6 +610,7 @@ static ssize_t driver_override_show(struct device *dev,
 #ifdef CONFIG_NUMA
 	&dev_attr_numa_node.attr,
 #endif
+	&dev_attr_dev_num.attr,
 	&dev_attr_server_monitor_pending.attr,
 	&dev_attr_client_monitor_pending.attr,
 	&dev_attr_server_monitor_latency.attr,
-- 
1.8.3.1