[WATCHDOG] mpc5200_wdt clean-up

* Add MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
* Add mandatory WDIOC_GETSTATUS and WDIOC_GETBOOTSTATUS ioctl's.
* If unknown ioctl is used we should return -ENOTTY.
* All watchdog device drivers are VFSs (Virtual File Systems).
  We thus return a nonseekable_open(inode, file) when we open the VFS.
* Make sure that /dev/watchdog can be opened by 1 parent
* Add spin-locking to prevent that forked children can disturb
  each other's operations.

Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

1 files changed, 30 insertions, 2 deletions

diff --git a/drivers/char/watchdog/mpc5200_wdt.c b/drivers/char/watchdog/mpc5200_wdt.c
index cc3299c03683..564143d40610 100644
--- a/drivers/char/watchdog/mpc5200_wdt.c
+++ b/drivers/char/watchdog/mpc5200_wdt.c
@@ -3,6 +3,7 @@
 #include <linux/miscdevice.h>
 #include <linux/watchdog.h>
 #include <linux/io.h>
+#include <linux/spinlock.h>
 #include <asm/of_platform.h>
 #include <asm/uaccess.h>
 #include <asm/mpc52xx.h>
@@ -19,8 +20,11 @@ struct mpc5200_wdt {
         struct miscdevice miscdev;
         struct resource mem;
         struct mpc52xx_gpt __iomem *regs;
+        spinlock_t io_lock;
 };
 
+/* is_active stores wether or not the /dev/watchdog device is opened */
+static unsigned long is_active;
 
 /* misc devices don't provide a way, to get back to 'dev' or 'miscdev' from
  * file operations, which sucks. But there can be max 1 watchdog anyway, so...
@@ -47,24 +51,31 @@ static int mpc5200_wdt_get_timeout(struct mpc5200_wdt *wdt)
 /* watchdog operations */
 static int mpc5200_wdt_start(struct mpc5200_wdt *wdt)
 {
+        spin_lock(&wdt->io_lock);
         /* disable */
         out_be32(&wdt->regs->mode, 0);
         /* set timeout, with maximum prescaler */
         out_be32(&wdt->regs->count, 0x0 | wdt->count);
         /* enable watchdog */
         out_be32(&wdt->regs->mode, GPT_MODE_CE | GPT_MODE_WDT | GPT_MODE_MS_TIMER);
+        spin_unlock(&wdt->io_lock);
 
         return 0;
 }
 static int mpc5200_wdt_ping(struct mpc5200_wdt *wdt)
 {
+        spin_lock(&wdt->io_lock);
         /* writing A5 to OCPW resets the watchdog */
         out_be32(&wdt->regs->mode, 0xA5000000 | (0xffffff & in_be32(&wdt->regs->mode)));
+        spin_unlock(&wdt->io_lock);
         return 0;
 }
 static int mpc5200_wdt_stop(struct mpc5200_wdt *wdt)
 {
+        spin_lock(&wdt->io_lock);
+        /* disable */
         out_be32(&wdt->regs->mode, 0);
+        spin_unlock(&wdt->io_lock);
         return 0;
 }
 
@@ -91,11 +102,17 @@ static int mpc5200_wdt_ioctl(struct inode *inode, struct file *file,
 
         switch (cmd) {
         case WDIOC_GETSUPPORT:
-                ret = copy_to_user(data, &mpc5200_wdt_info, sizeof(mpc5200_wdt_info));
+                ret = copy_to_user(data, &mpc5200_wdt_info,
+                        sizeof(mpc5200_wdt_info));
                 if (ret)
                         ret = -EFAULT;
                 break;
 
+        case WDIOC_GETSTATUS:
+        case WDIOC_GETBOOTSTATUS:
+                ret = put_user(0, data);
+                break;
+
         case WDIOC_KEEPALIVE:
                 mpc5200_wdt_ping(wdt);
                 break;
@@ -112,15 +129,23 @@ static int mpc5200_wdt_ioctl(struct inode *inode, struct file *file,
                 timeout = mpc5200_wdt_get_timeout(wdt);
                 ret = put_user(timeout, data);
                 break;
+
+        default:
+                ret = -ENOTTY;
         }
         return ret;
 }
 static int mpc5200_wdt_open(struct inode *inode, struct file *file)
 {
+        /* /dev/watchdog can only be opened once */
+        if (test_and_set_bit(0, &is_active))
+                return -EBUSY;
+
+        /* Set and activate the watchdog */
         mpc5200_wdt_set_timeout(wdt_global, 30);
         mpc5200_wdt_start(wdt_global);
         file->private_data = wdt_global;
-        return 0;
+        return nonseekable_open(inode, file);
 }
 static int mpc5200_wdt_release(struct inode *inode, struct file *file)
 {
@@ -129,6 +154,7 @@ static int mpc5200_wdt_release(struct inode *inode, struct file *file)
         mpc5200_wdt_stop(wdt);
         wdt->count = 0;         /* == disabled */
 #endif
+        clear_bit(0, &is_active);
         return 0;
 }
 
@@ -173,6 +199,7 @@ static int mpc5200_wdt_probe(struct of_device *op, const struct of_device_id *ma
         }
 
         dev_set_drvdata(&op->dev, wdt);
+        spin_lock_init(&wdt->io_lock);
 
         wdt->miscdev = (struct miscdevice) {
                 .minor  = WATCHDOG_MINOR,
@@ -256,3 +283,4 @@ module_exit(mpc5200_wdt_exit);
 
 MODULE_AUTHOR("Domen Puncer <domen.puncer@telargo.com>");
 MODULE_LICENSE("Dual BSD/GPL");
+MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);