rapidio: update enumerator registration mechanism

Update enumeration/discovery method registration mechanism to allow
loading enumeration/discovery methods before all mports are registered.

Existing statically linked RapidIO subsystem expects that all available
RapidIO mport devices are initialized and registered before the
enumeration/discovery method is registered.  Switching to loadable mport
device drivers creates situation when mport device driver can be loaded
after enumeration/discovery method is attached (e.g., loadable mport
driver in a system with statically linked RapidIO core and enumerator).
This also will happen in a system with hot-pluggable RapidIO controllers.

To remove the dependency on the initialization/registration order this
patch introduces enumeration/discovery registration mechanism that
supports arbitrary registration order of mports and enumerator/discovery
methods.

The following registration rules are implemented:
- only one enumeration/discovery method can be registered for given mport ID
  (including RIO_MPORT_ANY);
- when new enumeration/discovery methods tries to attach to the registered mport
  device, method with matching mport ID will replace a default method previously
  registered for given mport (if any);
- enumeration/discovery method with target ID=RIO_MPORT_ANY will be attached
  only to mports that do not have another enumerator attached to them;
- when new mport device is registered with RapidIO subsystem, registration
  routine searches for the enumeration/discovery method with the best matching
  mport ID;

Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Li Yang <leoli@freescale.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Andre van Herk <andre.van.herk@Prodrive.nl>
Cc: Micha Nelissen <micha.nelissen@Prodrive.nl>
Cc: Stef van Os <stef.van.os@Prodrive.nl>
Cc: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 149 insertions, 48 deletions

diff --git a/drivers/rapidio/rio-scan.c b/drivers/rapidio/rio-scan.c
index 913950212605..ab837fdb2383 100644
--- a/drivers/rapidio/rio-scan.c
+++ b/drivers/rapidio/rio-scan.c
@@ -1162,6 +1162,7 @@ bail:
 }
 
 static struct rio_scan rio_scan_ops = {
+        .owner = THIS_MODULE,
         .enumerate = rio_enum_mport,
         .discover = rio_disc_mport,
 };
diff --git a/drivers/rapidio/rio-sysfs.c b/drivers/rapidio/rio-sysfs.c
index 864e52f193e1..0c4473e54f86 100644
--- a/drivers/rapidio/rio-sysfs.c
+++ b/drivers/rapidio/rio-sysfs.c
@@ -286,7 +286,6 @@ static ssize_t bus_scan_store(struct bus_type *bus, const char *buf,
                                 size_t count)
 {
         long val;
-        struct rio_mport *port = NULL;
         int rc;
 
         if (kstrtol(buf, 0, &val) < 0)
@@ -300,21 +299,7 @@ static ssize_t bus_scan_store(struct bus_type *bus, const char *buf,
         if (val < 0 || val >= RIO_MAX_MPORTS)
                 return -EINVAL;
 
-        port = rio_find_mport((int)val);
-
-        if (!port) {
-                pr_debug("RIO: %s: mport_%d not available\n",
-                         __func__, (int)val);
-                return -EINVAL;
-        }
-
-        if (!port->nscan)
-                return -EINVAL;
-
-        if (port->host_deviceid >= 0)
-                rc = port->nscan->enumerate(port, 0);
-        else
-                rc = port->nscan->discover(port, RIO_SCAN_ENUM_NO_WAIT);
+        rc = rio_mport_scan((int)val);
 exit:
         if (!rc)
                 rc = count;
diff --git a/drivers/rapidio/rio.c b/drivers/rapidio/rio.c
index b17d5218005e..5eb727cd0652 100644
--- a/drivers/rapidio/rio.c
+++ b/drivers/rapidio/rio.c
@@ -34,6 +34,7 @@ static LIST_HEAD(rio_devices);
 static DEFINE_SPINLOCK(rio_global_list_lock);
 
 static LIST_HEAD(rio_mports);
+static LIST_HEAD(rio_scans);
 static DEFINE_MUTEX(rio_mport_list_lock);
 static unsigned char next_portid;
 static DEFINE_SPINLOCK(rio_mmap_lock);
@@ -1602,34 +1603,73 @@ found:
  * rio_register_scan - enumeration/discovery method registration interface
  * @mport_id: mport device ID for which fabric scan routine has to be set
  *            (RIO_MPORT_ANY = set for all available mports)
- * @scan_ops: enumeration/discovery control structure
+ * @scan_ops: enumeration/discovery operations structure
+ *
+ * Registers enumeration/discovery operations with RapidIO subsystem and
+ * attaches it to the specified mport device (or all available mports
+ * if RIO_MPORT_ANY is specified).
  *
- * Assigns enumeration or discovery method to the specified mport device (or all
- * available mports if RIO_MPORT_ANY is specified).
  * Returns error if the mport already has an enumerator attached to it.
- * In case of RIO_MPORT_ANY ignores ports with valid scan routines and returns
- * an error if was unable to find at least one available mport.
+ * In case of RIO_MPORT_ANY skips mports with valid scan routines (no error).
  */
 int rio_register_scan(int mport_id, struct rio_scan *scan_ops)
 {
         struct rio_mport *port;
-        int rc = -EBUSY;
+        struct rio_scan_node *scan;
+        int rc = 0;
 
-        mutex_lock(&rio_mport_list_lock);
-        list_for_each_entry(port, &rio_mports, node) {
-                if (port->id == mport_id || mport_id == RIO_MPORT_ANY) {
-                        if (port->nscan && mport_id == RIO_MPORT_ANY)
-                                continue;
-                        else if (port->nscan)
-                                break;
+        pr_debug("RIO: %s for mport_id=%d\n", __func__, mport_id);
 
-                        port->nscan = scan_ops;
-                        rc = 0;
+        if ((mport_id != RIO_MPORT_ANY && mport_id >= RIO_MAX_MPORTS) ||
+            !scan_ops)
+                return -EINVAL;
 
-                        if (mport_id != RIO_MPORT_ANY)
-                                break;
+        mutex_lock(&rio_mport_list_lock);
+
+        /*
+         * Check if there is another enumerator already registered for
+         * the same mport ID (including RIO_MPORT_ANY). Multiple enumerators
+         * for the same mport ID are not supported.
+         */
+        list_for_each_entry(scan, &rio_scans, node) {
+                if (scan->mport_id == mport_id) {
+                        rc = -EBUSY;
+                        goto err_out;
                 }
         }
+
+        /*
+         * Allocate and initialize new scan registration node.
+         */
+        scan = kzalloc(sizeof(*scan), GFP_KERNEL);
+        if (!scan) {
+                rc = -ENOMEM;
+                goto err_out;
+        }
+
+        scan->mport_id = mport_id;
+        scan->ops = scan_ops;
+
+        /*
+         * Traverse the list of registered mports to attach this new scan.
+         *
+         * The new scan with matching mport ID overrides any previously attached
+         * scan assuming that old scan (if any) is the default one (based on the
+         * enumerator registration check above).
+         * If the new scan is the global one, it will be attached only to mports
+         * that do not have their own individual operations already attached.
+         */
+        list_for_each_entry(port, &rio_mports, node) {
+                if (port->id == mport_id) {
+                        port->nscan = scan_ops;
+                        break;
+                } else if (mport_id == RIO_MPORT_ANY && !port->nscan)
+                        port->nscan = scan_ops;
+        }
+
+        list_add_tail(&scan->node, &rio_scans);
+
+err_out:
         mutex_unlock(&rio_mport_list_lock);
 
         return rc;
@@ -1639,30 +1679,81 @@ EXPORT_SYMBOL_GPL(rio_register_scan);
 /**
  * rio_unregister_scan - removes enumeration/discovery method from mport
  * @mport_id: mport device ID for which fabric scan routine has to be
- *            unregistered (RIO_MPORT_ANY = set for all available mports)
+ *            unregistered (RIO_MPORT_ANY = apply to all mports that use
+ *            the specified scan_ops)
+ * @scan_ops: enumeration/discovery operations structure
  *
  * Removes enumeration or discovery method assigned to the specified mport
- * device (or all available mports if RIO_MPORT_ANY is specified).
+ * device. If RIO_MPORT_ANY is specified, removes the specified operations from
+ * all mports that have them attached.
  */
-int rio_unregister_scan(int mport_id)
+int rio_unregister_scan(int mport_id, struct rio_scan *scan_ops)
 {
         struct rio_mport *port;
+        struct rio_scan_node *scan;
+
+        pr_debug("RIO: %s for mport_id=%d\n", __func__, mport_id);
+
+        if (mport_id != RIO_MPORT_ANY && mport_id >= RIO_MAX_MPORTS)
+                return -EINVAL;
 
         mutex_lock(&rio_mport_list_lock);
-        list_for_each_entry(port, &rio_mports, node) {
-                if (port->id == mport_id || mport_id == RIO_MPORT_ANY) {
-                        if (port->nscan)
-                                port->nscan = NULL;
-                        if (mport_id != RIO_MPORT_ANY)
-                                break;
+
+        list_for_each_entry(port, &rio_mports, node)
+                if (port->id == mport_id ||
+                    (mport_id == RIO_MPORT_ANY && port->nscan == scan_ops))
+                        port->nscan = NULL;
+
+        list_for_each_entry(scan, &rio_scans, node)
+                if (scan->mport_id == mport_id) {
+                        list_del(&scan->node);
+                        kfree(scan);
                 }
-        }
+
         mutex_unlock(&rio_mport_list_lock);
 
         return 0;
 }
 EXPORT_SYMBOL_GPL(rio_unregister_scan);
 
+/**
+ * rio_mport_scan - execute enumeration/discovery on the specified mport
+ * @mport_id: number (ID) of mport device
+ */
+int rio_mport_scan(int mport_id)
+{
+        struct rio_mport *port = NULL;
+        int rc;
+
+        mutex_lock(&rio_mport_list_lock);
+        list_for_each_entry(port, &rio_mports, node) {
+                if (port->id == mport_id)
+                        goto found;
+        }
+        mutex_unlock(&rio_mport_list_lock);
+        return -ENODEV;
+found:
+        if (!port->nscan) {
+                mutex_unlock(&rio_mport_list_lock);
+                return -EINVAL;
+        }
+
+        if (!try_module_get(port->nscan->owner)) {
+                mutex_unlock(&rio_mport_list_lock);
+                return -ENODEV;
+        }
+
+        mutex_unlock(&rio_mport_list_lock);
+
+        if (port->host_deviceid >= 0)
+                rc = port->nscan->enumerate(port, 0);
+        else
+                rc = port->nscan->discover(port, RIO_SCAN_ENUM_NO_WAIT);
+
+        module_put(port->nscan->owner);
+        return rc;
+}
+
 static void rio_fixup_device(struct rio_dev *dev)
 {
 }
@@ -1691,7 +1782,10 @@ static void disc_work_handler(struct work_struct *_work)
         work = container_of(_work, struct rio_disc_work, work);
         pr_debug("RIO: discovery work for mport %d %s\n",
                  work->mport->id, work->mport->name);
-        work->mport->nscan->discover(work->mport, 0);
+        if (try_module_get(work->mport->nscan->owner)) {
+                work->mport->nscan->discover(work->mport, 0);
+                module_put(work->mport->nscan->owner);
+        }
 }
 
 int rio_init_mports(void)
@@ -1710,8 +1804,10 @@ int rio_init_mports(void)
         mutex_lock(&rio_mport_list_lock);
         list_for_each_entry(port, &rio_mports, node) {
                 if (port->host_deviceid >= 0) {
-                        if (port->nscan)
+                        if (port->nscan && try_module_get(port->nscan->owner)) {
                                 port->nscan->enumerate(port, 0);
+                                module_put(port->nscan->owner);
+                        }
                 } else
                         n++;
         }
@@ -1725,7 +1821,7 @@ int rio_init_mports(void)
          * for each of them. If the code below fails to allocate needed
          * resources, exit without error to keep results of enumeration
          * process (if any).
-         * TODO: Implement restart of dicovery process for all or
+         * TODO: Implement restart of discovery process for all or
          * individual discovering mports.
          */
         rio_wq = alloc_workqueue("riodisc", 0, 0);
@@ -1751,9 +1847,9 @@ int rio_init_mports(void)
                         n++;
                 }
         }
-        mutex_unlock(&rio_mport_list_lock);
 
         flush_workqueue(rio_wq);
+        mutex_unlock(&rio_mport_list_lock);
         pr_debug("RIO: destroy discovery workqueue\n");
         destroy_workqueue(rio_wq);
         kfree(work);
@@ -1784,6 +1880,8 @@ __setup("riohdid=", rio_hdid_setup);
 
 int rio_register_mport(struct rio_mport *port)
 {
+        struct rio_scan_node *scan = NULL;
+
         if (next_portid >= RIO_MAX_MPORTS) {
                 pr_err("RIO: reached specified max number of mports\n");
                 return 1;
@@ -1792,9 +1890,25 @@ int rio_register_mport(struct rio_mport *port)
         port->id = next_portid++;
         port->host_deviceid = rio_get_hdid(port->id);
         port->nscan = NULL;
+
         mutex_lock(&rio_mport_list_lock);
         list_add_tail(&port->node, &rio_mports);
+
+        /*
+         * Check if there are any registered enumeration/discovery operations
+         * that have to be attached to the added mport.
+         */
+        list_for_each_entry(scan, &rio_scans, node) {
+                if (port->id == scan->mport_id ||
+                    scan->mport_id == RIO_MPORT_ANY) {
+                        port->nscan = scan->ops;
+                        if (port->id == scan->mport_id)
+                                break;
+                }
+        }
         mutex_unlock(&rio_mport_list_lock);
+
+        pr_debug("RIO: %s %s id=%d\n", __func__, port->name, port->id);
         return 0;
 }
 
diff --git a/drivers/rapidio/rio.h b/drivers/rapidio/rio.h
index d59587762c76..085215cd8502 100644
--- a/drivers/rapidio/rio.h
+++ b/drivers/rapidio/rio.h
@@ -42,9 +42,10 @@ extern int rio_add_device(struct rio_dev *rdev);
 extern int rio_enable_rx_tx_port(struct rio_mport *port, int local, u16 destid,
                                  u8 hopcount, u8 port_num);
 extern int rio_register_scan(int mport_id, struct rio_scan *scan_ops);
-extern int rio_unregister_scan(int mport_id);
+extern int rio_unregister_scan(int mport_id, struct rio_scan *scan_ops);
 extern void rio_attach_device(struct rio_dev *rdev);
 extern struct rio_mport *rio_find_mport(int mport_id);
+extern int rio_mport_scan(int mport_id);
 
 /* Structures internal to the RIO core code */
 extern struct device_attribute rio_dev_attrs[];