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remarkable-linux/include/linux/watchdog.h
Hans de Goede e907df3272 watchdog: Add support for dynamically allocated watchdog_device structs 
If a driver's watchdog_device struct is part of a dynamically allocated
struct (which it often will be), merely locking the module is not enough,
even with a drivers module locked, the driver can be unbound from the device,
examples:
1) The root user can unbind it through sysfd
2) The i2c bus master driver being unloaded for an i2c watchdog

I will gladly admit that these are corner cases, but we still need to handle
them correctly.

The fix for this consists of 2 parts:
1) Add ref / unref operations, so that the driver can refcount the struct
   holding the watchdog_device struct and delay freeing it until any
   open filehandles referring to it are closed
2) Most driver operations will do IO on the device and the driver should not
   do any IO on the device after it has been unbound. Rather then letting each
   driver deal with this internally, it is better to ensure at the watchdog
   core level that no operations (other then unref) will get called after
   the driver has called watchdog_unregister_device(). This actually is the
   bulk of this patch.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
2012-05-30 07:55:31 +02:00

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/*
* Generic watchdog defines. Derived from..
*
* Berkshire PC Watchdog Defines
* by Ken Hollis <khollis@bitgate.com>
*
*/
#ifndef _LINUX_WATCHDOG_H
#define _LINUX_WATCHDOG_H
#include <linux/ioctl.h>
#include <linux/types.h>
#define WATCHDOG_IOCTL_BASE 'W'
struct watchdog_info {
__u32 options; /* Options the card/driver supports */
__u32 firmware_version; /* Firmware version of the card */
__u8 identity[32]; /* Identity of the board */
};
#define WDIOC_GETSUPPORT _IOR(WATCHDOG_IOCTL_BASE, 0, struct watchdog_info)
#define WDIOC_GETSTATUS _IOR(WATCHDOG_IOCTL_BASE, 1, int)
#define WDIOC_GETBOOTSTATUS _IOR(WATCHDOG_IOCTL_BASE, 2, int)
#define WDIOC_GETTEMP _IOR(WATCHDOG_IOCTL_BASE, 3, int)
#define WDIOC_SETOPTIONS _IOR(WATCHDOG_IOCTL_BASE, 4, int)
#define WDIOC_KEEPALIVE _IOR(WATCHDOG_IOCTL_BASE, 5, int)
#define WDIOC_SETTIMEOUT _IOWR(WATCHDOG_IOCTL_BASE, 6, int)
#define WDIOC_GETTIMEOUT _IOR(WATCHDOG_IOCTL_BASE, 7, int)
#define WDIOC_SETPRETIMEOUT _IOWR(WATCHDOG_IOCTL_BASE, 8, int)
#define WDIOC_GETPRETIMEOUT _IOR(WATCHDOG_IOCTL_BASE, 9, int)
#define WDIOC_GETTIMELEFT _IOR(WATCHDOG_IOCTL_BASE, 10, int)
#define WDIOF_UNKNOWN -1 /* Unknown flag error */
#define WDIOS_UNKNOWN -1 /* Unknown status error */
#define WDIOF_OVERHEAT 0x0001 /* Reset due to CPU overheat */
#define WDIOF_FANFAULT 0x0002 /* Fan failed */
#define WDIOF_EXTERN1 0x0004 /* External relay 1 */
#define WDIOF_EXTERN2 0x0008 /* External relay 2 */
#define WDIOF_POWERUNDER 0x0010 /* Power bad/power fault */
#define WDIOF_CARDRESET 0x0020 /* Card previously reset the CPU */
#define WDIOF_POWEROVER 0x0040 /* Power over voltage */
#define WDIOF_SETTIMEOUT 0x0080 /* Set timeout (in seconds) */
#define WDIOF_MAGICCLOSE 0x0100 /* Supports magic close char */
#define WDIOF_PRETIMEOUT 0x0200 /* Pretimeout (in seconds), get/set */
#define WDIOF_ALARMONLY 0x0400 /* Watchdog triggers a management or
other external alarm not a reboot */
#define WDIOF_KEEPALIVEPING 0x8000 /* Keep alive ping reply */
#define WDIOS_DISABLECARD 0x0001 /* Turn off the watchdog timer */
#define WDIOS_ENABLECARD 0x0002 /* Turn on the watchdog timer */
#define WDIOS_TEMPPANIC 0x0004 /* Kernel panic on temperature trip */
#ifdef __KERNEL__
#include <linux/bitops.h>
#include <linux/device.h>
#include <linux/cdev.h>
struct watchdog_ops;
struct watchdog_device;
/** struct watchdog_ops - The watchdog-devices operations
*
* @owner: The module owner.
* @start: The routine for starting the watchdog device.
* @stop: The routine for stopping the watchdog device.
* @ping: The routine that sends a keepalive ping to the watchdog device.
* @status: The routine that shows the status of the watchdog device.
* @set_timeout:The routine for setting the watchdog devices timeout value.
* @get_timeleft:The routine that get's the time that's left before a reset.
* @ref: The ref operation for dyn. allocated watchdog_device structs
* @unref: The unref operation for dyn. allocated watchdog_device structs
* @ioctl: The routines that handles extra ioctl calls.
*
* The watchdog_ops structure contains a list of low-level operations
* that control a watchdog device. It also contains the module that owns
* these operations. The start and stop function are mandatory, all other
* functions are optonal.
*/
struct watchdog_ops {
struct module *owner;
/* mandatory operations */
int (*start)(struct watchdog_device *);
int (*stop)(struct watchdog_device *);
/* optional operations */
int (*ping)(struct watchdog_device *);
unsigned int (*status)(struct watchdog_device *);
int (*set_timeout)(struct watchdog_device *, unsigned int);
unsigned int (*get_timeleft)(struct watchdog_device *);
void (*ref)(struct watchdog_device *);
void (*unref)(struct watchdog_device *);
long (*ioctl)(struct watchdog_device *, unsigned int, unsigned long);
};
/** struct watchdog_device - The structure that defines a watchdog device
*
* @id: The watchdog's ID. (Allocated by watchdog_register_device)
* @cdev: The watchdog's Character device.
* @dev: The device for our watchdog
* @parent: The parent bus device
* @info: Pointer to a watchdog_info structure.
* @ops: Pointer to the list of watchdog operations.
* @bootstatus: Status of the watchdog device at boot.
* @timeout: The watchdog devices timeout value.
* @min_timeout:The watchdog devices minimum timeout value.
* @max_timeout:The watchdog devices maximum timeout value.
* @driver-data:Pointer to the drivers private data.
* @lock: Lock for watchdog core internal use only.
* @status: Field that contains the devices internal status bits.
*
* The watchdog_device structure contains all information about a
* watchdog timer device.
*
* The driver-data field may not be accessed directly. It must be accessed
* via the watchdog_set_drvdata and watchdog_get_drvdata helpers.
*
* The lock field is for watchdog core internal use only and should not be
* touched.
*/
struct watchdog_device {
int id;
struct cdev cdev;
struct device *dev;
struct device *parent;
const struct watchdog_info *info;
const struct watchdog_ops *ops;
unsigned int bootstatus;
unsigned int timeout;
unsigned int min_timeout;
unsigned int max_timeout;
void *driver_data;
struct mutex lock;
unsigned long status;
/* Bit numbers for status flags */
#define WDOG_ACTIVE 0 /* Is the watchdog running/active */
#define WDOG_DEV_OPEN 1 /* Opened via /dev/watchdog ? */
#define WDOG_ALLOW_RELEASE 2 /* Did we receive the magic char ? */
#define WDOG_NO_WAY_OUT 3 /* Is 'nowayout' feature set ? */
#define WDOG_UNREGISTERED 4 /* Has the device been unregistered */
};
#ifdef CONFIG_WATCHDOG_NOWAYOUT
#define WATCHDOG_NOWAYOUT 1
#define WATCHDOG_NOWAYOUT_INIT_STATUS (1 << WDOG_NO_WAY_OUT)
#else
#define WATCHDOG_NOWAYOUT 0
#define WATCHDOG_NOWAYOUT_INIT_STATUS 0
#endif
/* Use the following function to check wether or not the watchdog is active */
static inline bool watchdog_active(struct watchdog_device *wdd)
{
return test_bit(WDOG_ACTIVE, &wdd->status);
}
/* Use the following function to set the nowayout feature */
static inline void watchdog_set_nowayout(struct watchdog_device *wdd, bool nowayout)
{
if (nowayout)
set_bit(WDOG_NO_WAY_OUT, &wdd->status);
}
/* Use the following functions to manipulate watchdog driver specific data */
static inline void watchdog_set_drvdata(struct watchdog_device *wdd, void *data)
{
wdd->driver_data = data;
}
static inline void *watchdog_get_drvdata(struct watchdog_device *wdd)
{
return wdd->driver_data;
}
/* drivers/watchdog/core/watchdog_core.c */
extern int watchdog_register_device(struct watchdog_device *);
extern void watchdog_unregister_device(struct watchdog_device *);
#endif /* __KERNEL__ */
#endif /* ifndef _LINUX_WATCHDOG_H */
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