watchdog: Add multiple device support

We keep the old /dev/watchdog interface file for the first watchdog via
miscdev. This is basically a cut and paste of the relevant interface code
from the rtc driver layer tweaked for watchdog.

Revised to fix problems noted by Hans de Goede

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

5 files changed, 140 insertions, 50 deletions

diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
index 25fe4304f2fc..3c85fc7dc1f1 100644
--- a/Documentation/watchdog/watchdog-kernel-api.txt
+++ b/Documentation/watchdog/watchdog-kernel-api.txt
@@ -1,6 +1,6 @@
 The Linux WatchDog Timer Driver Core kernel API.
 ===============================================
-Last reviewed: 16-Mar-2012
+Last reviewed: 21-May-2012
 
 Wim Van Sebroeck <wim@iguana.be>
 
@@ -39,6 +39,8 @@ watchdog_device structure.
 The watchdog device structure looks like this:
 
 struct watchdog_device {
+        int id;
+        struct cdev cdev;
         const struct watchdog_info *info;
         const struct watchdog_ops *ops;
         unsigned int bootstatus;
@@ -50,6 +52,12 @@ struct watchdog_device {
 };
 
 It contains following fields:
+* id: set by watchdog_register_device, id 0 is special. It has both a
+  /dev/watchdog0 cdev (dynamic major, minor 0) as well as the old
+  /dev/watchdog miscdev. The id is set automatically when calling
+  watchdog_register_device.
+* cdev: cdev for the dynamic /dev/watchdog<id> device nodes. This
+  field is also populated by watchdog_register_device.
 * info: a pointer to a watchdog_info structure. This structure gives some
   additional information about the watchdog timer itself. (Like it's unique name)
 * ops: a pointer to the list of watchdog operations that the watchdog supports.
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 8598308278d3..5f9879369003 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -34,9 +34,12 @@
 #include <linux/kernel.h>       /* For printk/panic/... */
 #include <linux/watchdog.h>     /* For watchdog specific items */
 #include <linux/init.h>         /* For __init/__exit/... */
+#include <linux/idr.h>          /* For ida_* macros */
 
 #include "watchdog_core.h"      /* For watchdog_dev_register/... */
 
+static DEFINE_IDA(watchdog_ida);
+
 /**
  * watchdog_register_device() - register a watchdog device
  * @wdd: watchdog device
@@ -49,7 +52,7 @@
  */
 int watchdog_register_device(struct watchdog_device *wdd)
 {
-        int ret;
+        int ret, id;
 
         if (wdd == NULL || wdd->info == NULL || wdd->ops == NULL)
                 return -EINVAL;
@@ -74,11 +77,28 @@ int watchdog_register_device(struct watchdog_device *wdd)
          * corrupted in a later stage then we expect a kernel panic!
          */
 
-        /* We only support 1 watchdog device via the /dev/watchdog interface */
+        id = ida_simple_get(&watchdog_ida, 0, MAX_DOGS, GFP_KERNEL);
+        if (id < 0)
+                return id;
+        wdd->id = id;
+
         ret = watchdog_dev_register(wdd);
         if (ret) {
-                pr_err("error registering /dev/watchdog (err=%d)\n", ret);
-                return ret;
+                ida_simple_remove(&watchdog_ida, id);
+                if (!(id == 0 && ret == -EBUSY))
+                        return ret;
+
+                /* Retry in case a legacy watchdog module exists */
+                id = ida_simple_get(&watchdog_ida, 1, MAX_DOGS, GFP_KERNEL);
+                if (id < 0)
+                        return id;
+                wdd->id = id;
+
+                ret = watchdog_dev_register(wdd);
+                if (ret) {
+                        ida_simple_remove(&watchdog_ida, id);
+                        return ret;
+                }
         }
 
         return 0;
@@ -102,9 +122,24 @@ void watchdog_unregister_device(struct watchdog_device *wdd)
         ret = watchdog_dev_unregister(wdd);
         if (ret)
                 pr_err("error unregistering /dev/watchdog (err=%d)\n", ret);
+        ida_simple_remove(&watchdog_ida, wdd->id);
 }
 EXPORT_SYMBOL_GPL(watchdog_unregister_device);
 
+static int __init watchdog_init(void)
+{
+        return watchdog_dev_init();
+}
+
+static void __exit watchdog_exit(void)
+{
+        watchdog_dev_exit();
+        ida_destroy(&watchdog_ida);
+}
+
+subsys_initcall(watchdog_init);
+module_exit(watchdog_exit);
+
 MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
 MODULE_AUTHOR("Wim Van Sebroeck <wim@iguana.be>");
 MODULE_DESCRIPTION("WatchDog Timer Driver Core");
diff --git a/drivers/watchdog/watchdog_core.h b/drivers/watchdog/watchdog_core.h
index 80503f229385..6c951418fca7 100644
--- a/drivers/watchdog/watchdog_core.h
+++ b/drivers/watchdog/watchdog_core.h
@@ -26,8 +26,12 @@
  *      This material is provided "AS-IS" and at no charge.
  */
 
+#define MAX_DOGS        32      /* Maximum number of watchdog devices */
+
 /*
  *      Functions/procedures to be called by the core
  */
 extern int watchdog_dev_register(struct watchdog_device *);
 extern int watchdog_dev_unregister(struct watchdog_device *);
+extern int __init watchdog_dev_init(void);
+extern void __exit watchdog_dev_exit(void);
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index beaf9cb5541a..3b22582bcb04 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -44,10 +44,10 @@
 
 #include "watchdog_core.h"
 
-/* make sure we only register one /dev/watchdog device */
-static unsigned long watchdog_dev_busy;
+/* the dev_t structure to store the dynamically allocated watchdog devices */
+static dev_t watchdog_devt;
 /* the watchdog device behind /dev/watchdog */
-static struct watchdog_device *wdd;
+static struct watchdog_device *old_wdd;
 
 /*
  *      watchdog_ping: ping the watchdog.
@@ -138,6 +138,7 @@ static int watchdog_stop(struct watchdog_device *wddev)
 static ssize_t watchdog_write(struct file *file, const char __user *data,
                                                 size_t len, loff_t *ppos)
 {
+        struct watchdog_device *wdd = file->private_data;
         size_t i;
         char c;