hyperv: Implement netvsc_get_channels() ethool op

This adds support for reporting the actual and maximum combined channels
count of the hv_netvsc driver via 'ethtool --show-channels'.

This required adding 'max_chn' to 'struct netvsc_device', and assigning
it 'rsscap.num_recv_que' in 'rndis_filter_device_add'. Now we can access
the combined maximum channel count via 'struct netvsc_device' in the
ethtool callback.

Signed-off-by: Andrew Schwartzmeyer <[e-mail]>
Signed-off-by: Haiyang Zhang <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/hyperv/hyperv_net.h

···
 
 	struct vmbus_channel *chn_table[NR_CPUS];
 	u32 send_table[VRSS_SEND_TAB_SIZE];
+	u32 max_chn;
 	u32 num_chn;
 	atomic_t queue_sends[NR_CPUS];
 

drivers/net/hyperv/netvsc_drv.c

···
 	strlcpy(info->fw_version, "N/A", sizeof(info->fw_version));
 }
 
+static void netvsc_get_channels(struct net_device *net,
+				struct ethtool_channels *channel)
+{
+	struct net_device_context *net_device_ctx = netdev_priv(net);
+	struct hv_device *dev = net_device_ctx->device_ctx;
+	struct netvsc_device *nvdev = hv_get_drvdata(dev);
+
+	if (nvdev) {
+		channel->max_combined	= nvdev->max_chn;
+		channel->combined_count = nvdev->num_chn;
+	}
+}
+
 static int netvsc_change_mtu(struct net_device *ndev, int mtu)
 {
 	struct net_device_context *ndevctx = netdev_priv(ndev);
···
 static const struct ethtool_ops ethtool_ops = {
 	.get_drvinfo	= netvsc_get_drvinfo,
 	.get_link	= ethtool_op_get_link,
+	.get_channels   = netvsc_get_channels,
 };
 
 static const struct net_device_ops device_ops = {

drivers/net/hyperv/rndis_filter.c

···
 
 	/* Initialize the rndis device */
 	net_device = hv_get_drvdata(dev);
+	net_device->max_chn = 1;
 	net_device->num_chn = 1;
 
 	net_device->extension = rndis_device;
···
 	if (ret || rsscap.num_recv_que < 2)
 		goto out;
 
+	net_device->max_chn = rsscap.num_recv_que;
 	net_device->num_chn = (num_online_cpus() < rsscap.num_recv_que) ?
 			       num_online_cpus() : rsscap.num_recv_que;
 	if (net_device->num_chn == 1)
···
 	ret = rndis_filter_set_rss_param(rndis_device, net_device->num_chn);
 
 out:
-	if (ret)
+	if (ret) {
+		net_device->max_chn = 1;
 		net_device->num_chn = 1;
+	}
 	return 0; /* return 0 because primary channel can be used alone */
 
 err_dev_remv: