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>

1 files changed, 82 insertions, 45 deletions

diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index beaf9cb5541..3b22582bcb0 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;
 
@@ -177,6 +178,7 @@ static ssize_t watchdog_write(struct file *file, const char __user *data,
 static long watchdog_ioctl(struct file *file, unsigned int cmd,
 							unsigned long arg)
 {
+	struct watchdog_device *wdd = file->private_data;
 	void __user *argp = (void __user *)arg;
 	int __user *p = argp;
 	unsigned int val;
@@ -249,11 +251,11 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
 }
 
 /*
- *	watchdog_open: open the /dev/watchdog device.
+ *	watchdog_open: open the /dev/watchdog* devices.
  *	@inode: inode of device
  *	@file: file handle to device
  *
- *	When the /dev/watchdog device gets opened, we start the watchdog.
+ *	When the /dev/watchdog* device gets opened, we start the watchdog.
  *	Watch out: the /dev/watchdog device is single open, so we make sure
  *	it can only be opened once.
  */
@@ -261,6 +263,13 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
 static int watchdog_open(struct inode *inode, struct file *file)
 {
 	int err = -EBUSY;
+	struct watchdog_device *wdd;
+
+	/* Get the corresponding watchdog device */
+	if (imajor(inode) == MISC_MAJOR)
+		wdd = old_wdd;
+	else
+		wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);
 
 	/* the watchdog is single open! */
 	if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
@@ -277,6 +286,8 @@ static int watchdog_open(struct inode *inode, struct file *file)
 	if (err < 0)
 		goto out_mod;
 
+	file->private_data = wdd;
+
 	/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
 	return nonseekable_open(inode, file);
 
@@ -288,9 +299,9 @@ out:
 }
 
 /*
- *      watchdog_release: release the /dev/watchdog device.
- *      @inode: inode of device
- *      @file: file handle to device
+ *	watchdog_release: release the watchdog device.
+ *	@inode: inode of device
+ *	@file: file handle to device
  *
  *	This is the code for when /dev/watchdog gets closed. We will only
  *	stop the watchdog when we have received the magic char (and nowayout
@@ -299,6 +310,7 @@ out:
 
 static int watchdog_release(struct inode *inode, struct file *file)
 {
+	struct watchdog_device *wdd = file->private_data;
 	int err = -EBUSY;
 
 	/*
@@ -340,62 +352,87 @@ static struct miscdevice watchdog_miscdev = {
 };
 
 /*
- *	watchdog_dev_register:
+ *	watchdog_dev_register: register a watchdog device
  *	@watchdog: watchdog device
  *
- *	Register a watchdog device as /dev/watchdog. /dev/watchdog
- *	is actually a miscdevice and thus we set it up like that.
+ *	Register a watchdog device including handling the legacy
+ *	/dev/watchdog node. /dev/watchdog is actually a miscdevice and
+ *	thus we set it up like that.
  */
 
 int watchdog_dev_register(struct watchdog_device *watchdog)
 {
-	int err;
-
-	/* Only one device can register for /dev/watchdog */
-	if (test_and_set_bit(0, &watchdog_dev_busy)) {
-		pr_err("only one watchdog can use /dev/watchdog\n");
-		return -EBUSY;
+	int err, devno;
+
+	if (watchdog->id == 0) {
+		err = misc_register(&watchdog_miscdev);
+		if (err != 0) {
+			pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
+				watchdog->info->identity, WATCHDOG_MINOR, err);
+			if (err == -EBUSY)
+				pr_err("%s: a legacy watchdog module is probably present.\n",
+					watchdog->info->identity);
+			return err;
+		}
+		old_wdd = watchdog;
 	}
 
-	wdd = watchdog;
-
-	err = misc_register(&watchdog_miscdev);
-	if (err != 0) {
-		pr_err("%s: cannot register miscdev on minor=%d (err=%d)\n",
-		       watchdog->info->identity, WATCHDOG_MINOR, err);
-		goto out;
+	/* Fill in the data structures */
+	devno = MKDEV(MAJOR(watchdog_devt), watchdog->id);
+	cdev_init(&watchdog->cdev, &watchdog_fops);
+	watchdog->cdev.owner = watchdog->ops->owner;
+
+	/* Add the device */
+	err  = cdev_add(&watchdog->cdev, devno, 1);
+	if (err) {
+		pr_err("watchdog%d unable to add device %d:%d\n",
+			watchdog->id,  MAJOR(watchdog_devt), watchdog->id);
+		if (watchdog->id == 0) {
+			misc_deregister(&watchdog_miscdev);
+			old_wdd = NULL;
+		}
 	}
-
-	return 0;
-
-out:
-	wdd = NULL;
-	clear_bit(0, &watchdog_dev_busy);
 	return err;
 }
 
 /*
- *	watchdog_dev_unregister:
+ *	watchdog_dev_unregister: unregister a watchdog device
  *	@watchdog: watchdog device
  *
- *	Deregister the /dev/watchdog device.
+ *	Unregister the watchdog and if needed the legacy /dev/watchdog device.
  */
 
 int watchdog_dev_unregister(struct watchdog_device *watchdog)
 {
-	/* Check that a watchdog device was registered in the past */
-	if (!test_bit(0, &watchdog_dev_busy) || !wdd)
-		return -ENODEV;
-
-	/* We can only unregister the watchdog device that was registered */
-	if (watchdog != wdd) {
-		pr_err("%s: watchdog was not registered as /dev/watchdog\n",
-		       watchdog->info->identity);
-		return -ENODEV;
+	cdev_del(&watchdog->cdev);
+	if (watchdog->id == 0) {
+		misc_deregister(&watchdog_miscdev);
+		old_wdd = NULL;
 	}
-
-	misc_deregister(&watchdog_miscdev);
-	wdd = NULL;
-	clear_bit(0, &watchdog_dev_busy);
 	return 0;
 }
+
+/*
+ *	watchdog_dev_init: init dev part of watchdog core
+ *
+ *	Allocate a range of chardev nodes to use for watchdog devices
+ */
+
+int __init watchdog_dev_init(void)
+{
+	int err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
+	if (err < 0)
+		pr_err("watchdog: unable to allocate char dev region\n");
+	return err;
+}
+
+/*
+ *	watchdog_dev_exit: exit dev part of watchdog core
+ *
+ *	Release the range of chardev nodes used for watchdog devices
+ */
+
+void __exit watchdog_dev_exit(void)
+{
+	unregister_chrdev_region(watchdog_devt, MAX_DOGS);
+}