firewire: reread config ROM when device reset the bus

When a device changes its configuration ROM, it announces this with a
bus reset.  firewire-core has to check which node initiated a bus reset
and whether any unit directories went away or were added on this node.

Tested with an IOI FWB-IDE01AB which has its link-on bit set if bus
power is available but does not respond to ROM read requests if self
power is off.  This implements
  - recognition of the units if self power is switched on after fw-core
    gave up the initial attempt to read the config ROM,
  - shutdown of the units when self power is switched off.

Also tested with a second PC running Linux/ieee1394.  When the eth1394
driver is inserted and removed on that node, fw-core now notices the
addition and removal of the IPv4 unit on the ieee1394 node.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/fw-card.c

@@ -331,7 +331,7 @@ fw_card_bm_work(struct work_struct *work)
 		 */
 		spin_unlock_irqrestore(&card->lock, flags);
 		goto out;
-	} else if (root_device->config_rom[2] & BIB_CMC) {
+	} else if (root_device->cmc) {
 		/*
 		 * FIXME: I suppose we should set the cmstr bit in the
 		 * STATE_CLEAR register of this node, as described in

drivers/firewire/fw-cdev.c

@@ -269,21 +269,28 @@ static int ioctl_get_info(struct client *client, void *buffer)
 {
 	struct fw_cdev_get_info *get_info = buffer;
 	struct fw_cdev_event_bus_reset bus_reset;
+	unsigned long ret = 0;
 
 	client->version = get_info->version;
 	get_info->version = FW_CDEV_VERSION;
 
+	down_read(&fw_device_rwsem);
+
 	if (get_info->rom != 0) {
 		void __user *uptr = u64_to_uptr(get_info->rom);
 		size_t want = get_info->rom_length;
 		size_t have = client->device->config_rom_length * 4;
 
-		if (copy_to_user(uptr, client->device->config_rom,
-				 min(want, have)))
-			return -EFAULT;
+		ret = copy_to_user(uptr, client->device->config_rom,
+				   min(want, have));
 	}
 	get_info->rom_length = client->device->config_rom_length * 4;
 
+	up_read(&fw_device_rwsem);
+
+	if (ret != 0)
+		return -EFAULT;
+
 	client->bus_reset_closure = get_info->bus_reset_closure;
 	if (get_info->bus_reset != 0) {
 		void __user *uptr = u64_to_uptr(get_info->bus_reset);