ipmi: allow dynamic BMC version information

Currently, it's up to the IPMI SMIs to provide the product & version
details of BMCs behind registered IPMI SMI interfaces. This device ID is
provided on SMI regsitration, and kept around for all future queries.

However, this version information isn't always static. For example, a
BMC may be upgraded at runtime, making the old version information
stale.

This change allows querying the BMC device ID & version information
dynamically. If no static device_id argument is provided to
ipmi_register_smi, then the IPMI core code will perform a Get Device ID
IPMI command to query the version information when needed. We keep a
short-term cache of this information so we don't need to re-query
for every attribute access.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>

I basically rewrote this, I fixed some locking issues and simplified
things.  Same functional change, though.

Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/ipmi_msghandler.c

@@ -159,6 +159,9 @@ static struct proc_dir_entry *proc_ipmi_root;
  */
 #define IPMI_REQUEST_EV_TIME	(1000 / (IPMI_TIMEOUT_TIME))
 
+/* How long should we cache dynamic device IDs? */
+#define IPMI_DYN_DEV_ID_EXPIRY	(10 * HZ)
+
 /*
  * The main "user" data structure.
  */
@@ -264,8 +267,12 @@ struct ipmi_proc_entry {
 
 struct bmc_device {
 	struct platform_device pdev;
-	struct ipmi_device_id  id;
 	struct list_head       intfs;
+	struct ipmi_device_id  id;
+	struct ipmi_device_id  fetch_id;
+	int                    dyn_id_set;
+	unsigned long          dyn_id_expiry;
+	struct mutex           dyn_mutex; /* protects id & dyn* fields */
 	unsigned char          guid[16];
 	int                    guid_set;
 	struct kref	       usecount;
@@ -402,6 +409,13 @@ struct ipmi_smi {
 	/* Used for wake ups at startup. */
 	wait_queue_head_t waitq;
 
+	/*
+	 * Prevents the interface from being unregistered when the
+	 * interface is used by being looked up through the BMC
+	 * structure.
+	 */
+	struct mutex bmc_reg_mutex;
+
 	struct bmc_device *bmc;
 	bool bmc_registered;
 	struct list_head bmc_link;
@@ -491,6 +505,11 @@ struct ipmi_smi {
 	 * interface comes in with a NULL user, call this routine with
 	 * it.  Note that the message will still be freed by the
 	 * caller.  This only works on the system interface.
+	 *
+	 * The only user outside of initialization an panic handling is
+	 * the dynamic device id fetching, so no mutex is currently
+	 * required on this.  If more users come along, some sort of
+	 * mutex will be required.
 	 */
 	void (*null_user_handler)(ipmi_smi_t intf, struct ipmi_recv_msg *msg);
 
@@ -2081,14 +2100,158 @@ int ipmi_request_supply_msgs(ipmi_user_t          user,
 }
 EXPORT_SYMBOL(ipmi_request_supply_msgs);
 
+static void bmc_device_id_handler(ipmi_smi_t intf, struct ipmi_recv_msg *msg)
+{
+	int rv;
+
+	if ((msg->addr.addr_type != IPMI_SYSTEM_INTERFACE_ADDR_TYPE)
+			|| (msg->msg.netfn != IPMI_NETFN_APP_RESPONSE)
+			|| (msg->msg.cmd != IPMI_GET_DEVICE_ID_CMD)) {
+		pr_warn(PFX "invalid device_id msg: addr_type=%d netfn=%x cmd=%x\n",
+			msg->addr.addr_type, msg->msg.netfn, msg->msg.cmd);
+		return;
+	}
+
+	rv = ipmi_demangle_device_id(msg->msg.netfn, msg->msg.cmd,
+			msg->msg.data, msg->msg.data_len, &intf->bmc->fetch_id);
+	if (rv) {
+		pr_warn(PFX "device id demangle failed: %d\n", rv);
+		intf->bmc->dyn_id_set = 0;
+	} else {
+		/*
+		 * Make sure the id data is available before setting
+		 * dyn_id_set.
+		 */
+		smp_wmb();
+		intf->bmc->dyn_id_set = 1;
+	}
+
+	wake_up(&intf->waitq);
+}
+
+static int
+send_get_device_id_cmd(ipmi_smi_t intf)
+{
+	struct ipmi_system_interface_addr si;
+	struct kernel_ipmi_msg msg;
+
+	si.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
+	si.channel = IPMI_BMC_CHANNEL;
+	si.lun = 0;
+
+	msg.netfn = IPMI_NETFN_APP_REQUEST;
+	msg.cmd = IPMI_GET_DEVICE_ID_CMD;
+	msg.data = NULL;
+	msg.data_len = 0;
+
+	return i_ipmi_request(NULL,
+			      intf,
+			      (struct ipmi_addr *) &si,
+			      0,
+			      &msg,
+			      intf,
+			      NULL,
+			      NULL,
+			      0,
+			      intf->channels[0].address,
+			      intf->channels[0].lun,
+			      -1, 0);
+}
+
+static int __get_device_id(ipmi_smi_t intf, struct bmc_device *bmc)
+{
+	int rv;
+
+	bmc->dyn_id_set = 2;
+
+	intf->null_user_handler = bmc_device_id_handler;
+
+	rv = send_get_device_id_cmd(intf);
+	if (rv)
+		return rv;
+
+	wait_event(intf->waitq, bmc->dyn_id_set != 2);
+
+	if (!bmc->dyn_id_set)
+		rv = -EIO; /* Something went wrong in the fetch. */
+
+	/* dyn_id_set makes the id data available. */
+	smp_rmb();
+
+	intf->null_user_handler = NULL;
+
+	return rv;
+}
+
+/*
+ * Fetch the device id for the bmc/interface.  You must pass in either
+ * bmc or intf, this code will get the other one.  If the data has
+ * been recently fetched, this will just use the cached data.  Otherwise
+ * it will run a new fetch.
+ *
+ * Except for the first time this is called (in ipmi_register_smi()),
+ * this will always return good data;
+ */
 static int bmc_get_device_id(ipmi_smi_t intf, struct bmc_device *bmc,
 			     struct ipmi_device_id *id)
 {
-	if (!bmc)
+	int rv = 0;
+	int prev_dyn_id_set;
+
+	if (!intf) {
+		mutex_lock(&bmc->dyn_mutex);
+retry_bmc_lock:
+		if (list_empty(&bmc->intfs)) {
+			mutex_unlock(&bmc->dyn_mutex);
+			return -ENOENT;
+		}
+		intf = list_first_entry(&bmc->intfs, struct ipmi_smi,
+					bmc_link);
+		kref_get(&intf->refcount);
+		mutex_unlock(&bmc->dyn_mutex);
+		mutex_lock(&intf->bmc_reg_mutex);
+		mutex_lock(&bmc->dyn_mutex);
+		if (intf != list_first_entry(&bmc->intfs, struct ipmi_smi,
+					     bmc_link)) {
+			mutex_unlock(&intf->bmc_reg_mutex);
+			kref_put(&intf->refcount, intf_free);
+			goto retry_bmc_lock;
+		}
+	} else {
+		mutex_lock(&intf->bmc_reg_mutex);
 		bmc = intf->bmc;
+		mutex_lock(&bmc->dyn_mutex);
+		kref_get(&intf->refcount);
+	}
 
-	*id = bmc->id;
-	return 0;
+	/* If we have a valid and current ID, just return that. */
+	if (bmc->dyn_id_set && time_is_after_jiffies(bmc->dyn_id_expiry))
+		goto out;
+
+	prev_dyn_id_set = bmc->dyn_id_set;
+
+	rv = __get_device_id(intf, bmc);
+	if (rv)
+		goto out;
+
+	memcpy(&bmc->id, &bmc->fetch_id, sizeof(bmc->id));
+
+	bmc->dyn_id_expiry = jiffies + IPMI_DYN_DEV_ID_EXPIRY;
+
+out:
+	if (rv && prev_dyn_id_set) {
+		rv = 0; /* Ignore failures if we have previous data. */
+		bmc->dyn_id_set = prev_dyn_id_set;
+	}
+
+	if (id)
+		*id = bmc->id;
+
+	mutex_unlock(&bmc->dyn_mutex);
+	mutex_unlock(&intf->bmc_reg_mutex);
+
+	kref_put(&intf->refcount, intf_free);
+	return rv;
 }
 
 #ifdef CONFIG_PROC_FS
@@ -2615,17 +2778,23 @@ static void ipmi_bmc_unregister(ipmi_smi_t intf)
 	if (!intf->bmc_registered)
 		return;
 
+	mutex_lock(&intf->bmc_reg_mutex);
+
 	sysfs_remove_link(&intf->si_dev->kobj, "bmc");
 	sysfs_remove_link(&bmc->pdev.dev.kobj, intf->my_dev_name);
 	kfree(intf->my_dev_name);
 	intf->my_dev_name = NULL;
 
-	mutex_lock(&ipmidriver_mutex);
+	mutex_lock(&bmc->dyn_mutex);
 	list_del(&intf->bmc_link);
+	mutex_unlock(&bmc->dyn_mutex);
 	intf->bmc = NULL;
+	mutex_lock(&ipmidriver_mutex);
 	kref_put(&bmc->usecount, cleanup_bmc_device);
 	mutex_unlock(&ipmidriver_mutex);
 	intf->bmc_registered = false;
+
+	mutex_unlock(&intf->bmc_reg_mutex);
 }
 
 static int ipmi_bmc_register(ipmi_smi_t intf, int ifnum)
@@ -2653,11 +2822,11 @@ static int ipmi_bmc_register(ipmi_smi_t intf, int ifnum)
 	 */
 	if (old_bmc) {
 		kfree(bmc);
-		mutex_lock(&ipmidriver_mutex);
+		bmc = old_bmc;
 		intf->bmc = old_bmc;
+		mutex_lock(&bmc->dyn_mutex);
 		list_add_tail(&intf->bmc_link, &bmc->intfs);
-		mutex_unlock(&ipmidriver_mutex);
-		bmc = old_bmc;
+		mutex_unlock(&bmc->dyn_mutex);
 
 		printk(KERN_INFO
 		       "ipmi: interfacing existing BMC (man_id: 0x%6.6x,"
@@ -2677,10 +2846,12 @@ static int ipmi_bmc_register(ipmi_smi_t intf, int ifnum)
 		bmc->pdev.dev.type = &bmc_device_type;
 		kref_init(&bmc->usecount);
 
-		rv = platform_device_register(&bmc->pdev);
-		mutex_lock(&ipmidriver_mutex);
+		intf->bmc = bmc;
+		mutex_lock(&bmc->dyn_mutex);
 		list_add_tail(&intf->bmc_link, &bmc->intfs);
-		mutex_unlock(&ipmidriver_mutex);
+		mutex_unlock(&bmc->dyn_mutex);
+
+		rv = platform_device_register(&bmc->pdev);
 		if (rv) {
 			printk(KERN_ERR
 			       "ipmi_msghandler:"
@@ -2743,18 +2914,20 @@ out_unlink1:
 	sysfs_remove_link(&intf->si_dev->kobj, "bmc");
 
 out_put_bmc:
-	mutex_lock(&ipmidriver_mutex);
+	mutex_lock(&bmc->dyn_mutex);
 	list_del(&intf->bmc_link);
+	mutex_unlock(&bmc->dyn_mutex);
 	intf->bmc = NULL;
+	mutex_lock(&ipmidriver_mutex);
 	kref_put(&bmc->usecount, cleanup_bmc_device);
 	mutex_unlock(&ipmidriver_mutex);
 	goto out;
 
 out_list_del:
-	mutex_lock(&ipmidriver_mutex);
+	mutex_lock(&bmc->dyn_mutex);
 	list_del(&intf->bmc_link);
+	mutex_unlock(&bmc->dyn_mutex);
 	intf->bmc = NULL;
-	mutex_unlock(&ipmidriver_mutex);
 	put_device(&bmc->pdev.dev);
 	goto out;
 }
@@ -2976,9 +3149,11 @@ int ipmi_register_smi(const struct ipmi_smi_handlers *handlers,
 		return -ENOMEM;
 	}
 	INIT_LIST_HEAD(&intf->bmc->intfs);
+	mutex_init(&intf->bmc->dyn_mutex);
+	INIT_LIST_HEAD(&intf->bmc_link);
+	mutex_init(&intf->bmc_reg_mutex);
 	intf->intf_num = -1; /* Mark it invalid for now. */
 	kref_init(&intf->refcount);
-	intf->bmc->id = *device_id;
 	intf->si_dev = si_dev;
 	for (j = 0; j < IPMI_MAX_CHANNELS; j++) {
 		intf->channels[j].address = IPMI_BMC_SLAVE_ADDR;