linux-toradex.git/drivers/watchdog/watchdog_dev.c, branch v3.11

watchdog: core: don't try to stop device if not running

2013-07-11T19:14:39+00:00

A watchdog device may be stopped from userspace using WDIOC_SETOPTIONS
ioctl and flag WDIOS_DISABLECARD. If the device is closed after this
operation, watchdog_release() is called and status bits checked for
stopping it. Besides, if the device has not been unregistered a critical
message "watchdog did not stop!" is printed, although the ioctl may have
successfully stopped it already.

Without the patch a user application sample code like this will successfully
stop the watchdog, but the kernel will output the message
"watchdog did not stop!":

	wd_fd = open("/dev/watchdog", O_RDWR);

	flags = WDIOS_DISABLECARD;
	ioctl(wd_fd, WDIOC_SETOPTIONS, &flags);

	close(wd_fd);

Signed-off-by: Hector Palacios 
Reviewed-by: Guenter Roeck 
Signed-off-by: Wim Van Sebroeck

watchdog: Fix race condition in registration code

2013-05-09T06:13:41+00:00

A race condition exists when registering the first watchdog device.
Sequence of events:

- watchdog_register_device calls watchdog_dev_register
- watchdog_dev_register creates the watchdog misc device by calling
  misc_register.
  At that time, the matching character device (/dev/watchdog0) does not yet
  exist, and old_wdd is not set either.
- Userspace gets an event and opens /dev/watchdog
- watchdog_open is called and sets wdd = old_wdd, which is still NULL,
  and tries to dereference it. This causes the kernel to panic.

Seen with systemd trying to open /dev/watchdog immediately after
it was created.

Reported-by: Arkadiusz Miskiewicz 
Signed-off-by: Guenter Roeck 
Tested-by: Arkadiusz Miskiewicz 
Signed-off-by: Wim Van Sebroeck

watchdog: core: dt: add support for the timeout-sec dt property

2013-03-01T11:48:36+00:00

Add support for watchdog drivers to initialize/set the timeout field
of the watchdog_device structure. The timeout field is initialised
either with the module timeout parameter value (if valid) or with the
timeout-sec dt property (if valid). If both are invalid the initial
value is unchanged.

Signed-off-by: Fabio Porcedda 
Acked-by: Nicolas Ferre 
Signed-off-by: Wim Van Sebroeck

watchdog: core: fix WDIOC_GETSTATUS return value

2012-06-28T18:40:56+00:00

In commit 7a87982420e5e126bfefeb42232d1fd92052794e we added
a wrapper for the WDIOC_GETSTATUS ioctl call. The code results
however in a different behaviour: it returns an error if the
driver doesn't support the status operation. This is not
according to the API that says that when we don't support
the status operation, that we just should return a 0 value.
Only when the device isn't there anymore, we should return an
error.

Signed-off-by: Wim Van Sebroeck

watchdog: Add support for dynamically allocated watchdog_device structs

2012-05-30T05:55:31+00:00

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 
Signed-off-by: Wim Van Sebroeck

watchdog: Add Locking support

2012-05-30T05:55:23+00:00

This patch fixes some potential multithreading issues, despite only
allowing one process to open the /dev/watchdog device, we can still get
called multiple times at the same time, since a program could be using thread,
or could share the fd after a fork.

This causes 2 potential problems:
1) watchdog_start / open do an unlocked test_n_set / test_n_clear,
   if these 2 race, the watchdog could be stopped while the active
   bit indicates it is running or visa versa.

2) Most watchdog_dev drivers probably assume that only one
   watchdog-op will get called at a time, this is not necessary
   true atm.

Signed-off-by: Hans de Goede 
Signed-off-by: Wim Van Sebroeck

watchdog: watchdog_dev: Rewrite wrapper code

2012-05-30T05:55:17+00:00

Rewrite and extend the wrapper code so that we can easily introduce
locking (this to be able to prevent potential multithreading issues).

Signed-off-by: Hans de Goede 
Signed-off-by: Wim Van Sebroeck

watchdog: use dev_ functions

2012-05-30T05:54:57+00:00

While they are registered all our watchdogs now have a valid device object
so we can in turn use that to report problems nicely.

Signed-off-by: Alan Cox 
Signed-off-by: Hans de Goede 
Signed-off-by: Wim Van Sebroeck

watchdog: create all the proper device files

2012-05-30T05:54:46+00:00

Create the watchdog class and it's associated devices.

Signed-off-by: Alan Cox 
Signed-off-by: Hans de Goede 
Signed-off-by: Wim Van Sebroeck

watchdog: Add multiple device support

2012-05-30T05:54:25+00:00

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 
Signed-off-by: Hans de Goede 
Signed-off-by: Tomas Winkler 
Signed-off-by: Wim Van Sebroeck