IB/umad: Increase maximum devices supported

Some large systems may support more than IB_UMAD_MAX_PORTS
(currently 64).

This change allows us to support more ports in a backwards-compatible
manner.  The first IB_UMAD_MAX_PORTS keep the same major/minor device
numbers they've always had.

If there are more than IB_UMAD_MAX_PORTS, we then dynamically request
a new major device number (new minors start at 0).

Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 44 insertions, 6 deletions

diff --git a/drivers/infiniband/core/user_mad.c b/drivers/infiniband/core/user_mad.c
index 5a66bd062389..57818aea9967 100644
--- a/drivers/infiniband/core/user_mad.c
+++ b/drivers/infiniband/core/user_mad.c
@@ -971,6 +971,28 @@ static ssize_t show_abi_version(struct class *class, char *buf)
 }
 static CLASS_ATTR(abi_version, S_IRUGO, show_abi_version, NULL);
 
+static dev_t overflow_maj;
+static DECLARE_BITMAP(overflow_map, IB_UMAD_MAX_PORTS);
+static int find_overflow_devnum(void)
+{
+        int ret;
+
+        if (!overflow_maj) {
+                ret = alloc_chrdev_region(&overflow_maj, 0, IB_UMAD_MAX_PORTS * 2,
+                                          "infiniband_mad");
+                if (ret) {
+                        printk(KERN_ERR "user_mad: couldn't register dynamic device number\n");
+                        return ret;
+                }
+        }
+
+        ret = find_first_zero_bit(overflow_map, IB_UMAD_MAX_PORTS);
+        if (ret >= IB_UMAD_MAX_PORTS)
+                return -1;
+
+        return ret;
+}
+
 static int ib_umad_init_port(struct ib_device *device, int port_num,
                              struct ib_umad_port *port)
 {
@@ -981,11 +1003,19 @@ static int ib_umad_init_port(struct ib_device *device, int port_num,
         devnum = find_first_zero_bit(dev_map, IB_UMAD_MAX_PORTS);
         if (devnum >= IB_UMAD_MAX_PORTS) {
                 spin_unlock(&port_lock);
-                return -1;
+                devnum = find_overflow_devnum();
+                if (devnum < 0)
+                        return -1;
+
+                spin_lock(&port_lock);
+                port->dev_num = devnum + IB_UMAD_MAX_PORTS;
+                base = devnum + overflow_maj;
+                set_bit(devnum, overflow_map);
+        } else {
+                port->dev_num = devnum;
+                base = devnum + base_dev;
+                set_bit(devnum, dev_map);
         }
-        port->dev_num = devnum;
-        base = devnum + base_dev;
-        set_bit(devnum, dev_map);
         spin_unlock(&port_lock);
 
         port->ib_dev   = device;
@@ -1042,7 +1072,10 @@ err_dev:
 
 err_cdev:
         cdev_del(&port->cdev);
-        clear_bit(devnum, dev_map);
+        if (port->dev_num < IB_UMAD_MAX_PORTS)
+                clear_bit(devnum, dev_map);
+        else
+                clear_bit(devnum, overflow_map);
 
         return -1;
 }
@@ -1079,7 +1112,10 @@ static void ib_umad_kill_port(struct ib_umad_port *port)
 
         mutex_unlock(&port->file_mutex);
 
-        clear_bit(port->dev_num, dev_map);
+        if (port->dev_num < IB_UMAD_MAX_PORTS)
+                clear_bit(port->dev_num, dev_map);
+        else
+                clear_bit(port->dev_num - IB_UMAD_MAX_PORTS, overflow_map);
 }
 
 static void ib_umad_add_one(struct ib_device *device)
@@ -1187,6 +1223,8 @@ static void __exit ib_umad_cleanup(void)
         ib_unregister_client(&umad_client);
         class_destroy(umad_class);
         unregister_chrdev_region(base_dev, IB_UMAD_MAX_PORTS * 2);
+        if (overflow_maj)
+                unregister_chrdev_region(overflow_maj, IB_UMAD_MAX_PORTS * 2);
 }
 
 module_init(ib_umad_init);