Lines Matching refs:the
10 It also does not describe the API which can be used by user space to communicate
11 with a WatchDog Timer. If you want to know this then please read the following
14 So what does this document describe? It describes the API that can be used by
15 WatchDog Timer Drivers that want to use the WatchDog Timer Driver Core
17 the same code does not have to be reproduced each time. This also means that
18 a watchdog timer driver then only needs to provide the different routines
19 (operations) that control the watchdog timer (WDT).
23 Each watchdog timer driver that wants to use the WatchDog Timer Driver Core
36 device. The parameter of this routine is the pointer to the registered
41 the boot process.
64 /dev/watchdog0 cdev (dynamic major, minor 0) as well as the old
67 * cdev: cdev for the dynamic /dev/watchdog<id> device nodes. This
69 * dev: device under the watchdog class (created by watchdog_register_device).
70 * parent: set this to the parent device (or NULL) before calling
73 additional information about the watchdog timer itself. (Like it's unique name)
74 * ops: a pointer to the list of watchdog operations that the watchdog supports.
75 * timeout: the watchdog timer's timeout value (in seconds).
76 * min_timeout: the watchdog timer's minimum timeout value (in seconds).
77 * max_timeout: the watchdog timer's maximum timeout value (in seconds).
78 * bootstatus: status of the device after booting (reported with watchdog
80 * driver_data: a pointer to the drivers private data of a watchdog device.
81 This data should only be accessed via the watchdog_set_drvdata and
85 information about the status of the device (Like: is the watchdog timer
86 running/active, is the nowayout bit set, is the device opened via
87 the /dev/watchdog interface or not, ...).
108 It is important that you first define the module owner of the watchdog timer
109 driver's operations. This module owner will be used to lock the module when
110 the watchdog is active. (This to avoid a system crash when you unload the
113 If the watchdog_device struct is dynamically allocated, just locking the module
114 is not enough and a driver also needs to define the ref and unref operations to
115 ensure the structure holding the watchdog_device does not go away.
118 1) Add a kref struct to the same structure which is holding the watchdog_device
119 2) Define a release callback for the kref which frees the struct holding both
124 * Do not kfree() the struct holding both, the last kref_put will do this!
125 * *After* calling watchdog_unregister_device() call kref_put on the kref
129 * start: this is a pointer to the routine that starts the watchdog timer
131 The routine needs a pointer to the watchdog timer device structure as a
133 * stop: with this routine the watchdog timer device is being stopped.
134 The routine needs a pointer to the watchdog timer device structure as a
138 routine is being provided. This can be done by using a timer in the driver
139 that regularly sends a keepalive ping to the watchdog timer hardware.
141 Not all watchdog timer hardware supports the same functionality. That's why
144 * ping: this is the routine that sends a keepalive ping to the watchdog timer
146 The routine needs a pointer to the watchdog timer device structure as a
148 Most hardware that does not support this as a separate function uses the
149 start function to restart the watchdog timer hardware. And that's also what
150 the watchdog timer driver core does: to send a keepalive ping to the watchdog
151 timer hardware it will either use the ping operation (when available) or the
152 start operation (when the ping operation is not available).
153 (Note: the WDIOC_KEEPALIVE ioctl call will only be active when the
154 WDIOF_KEEPALIVEPING bit has been set in the option field on the watchdog's
156 * status: this routine checks the status of the watchdog timer device. The
157 status of the device is reported with watchdog WDIOF_* status flags/bits.
158 * set_timeout: this routine checks and changes the timeout of the watchdog
160 and -EIO for "could not write value to the watchdog". On success this
161 routine should set the timeout value of the watchdog_device to the
162 achieved timeout value (which may be different from the requested one
163 because the watchdog does not necessarily has a 1 second resolution).
164 (Note: the WDIOF_SETTIMEOUT needs to be set in the options field of the
166 * get_timeleft: this routines returns the time that's left before a reset.
167 * ref: the operation that calls kref_get on the kref of a dynamically
169 * unref: the operation that calls kref_put on the kref of a dynamically
173 if a command is not supported. The parameters that are passed to the ioctl
176 The status bits should (preferably) be set with the set_bit and clear_bit alike
179 is active or not. When the watchdog is active after booting, then you should
180 set this status bit (Note: when you register the watchdog timer device with
181 this bit set, then opening /dev/watchdog will skip the start operation)
182 * WDOG_DEV_OPEN: this status bit shows whether or not the watchdog device
184 (This bit should only be used by the WatchDog Timer Driver Core).
185 * WDOG_ALLOW_RELEASE: this bit stores whether or not the magic close character
186 has been sent (so that we can support the magic close feature).
187 (This bit should only be used by the WatchDog Timer Driver Core).
188 * WDOG_NO_WAY_OUT: this bit stores the nowayout setting for the watchdog.
189 If this bit is set then the watchdog timer will not be able to stop.
190 * WDOG_UNREGISTERED: this bit gets set by the WatchDog Timer Driver Core
196 To set the WDOG_NO_WAY_OUT status bit (before registering your watchdog
200 (this will set the value the same as CONFIG_WATCHDOG_NOWAYOUT) or
201 * use the following helper function:
204 Note: The WatchDog Timer Driver Core supports the magic close feature and
205 the nowayout feature. To use the magic close feature you must set the
206 WDIOF_MAGICCLOSE bit in the options field of the watchdog's info structure.
207 The nowayout feature will overrule the magic close feature.
209 To get or set driver specific data the following two helper functions should be
216 arguments of this function are the watchdog device where you want to add the
217 driver specific data to and a pointer to the data itself.
220 The argument of this function is the watchdog device where you want to retrieve
221 data from. The function returns the pointer to the driver specific data.
223 To initialize the timeout field, the following function can be used:
228 The watchdog_init_timeout function allows you to initialize the timeout field
229 using the module timeout parameter or by retrieving the timeout-sec property from
230 the device tree (if the module timeout parameter is invalid). Best practice is
231 to set the default timeout value as timeout value in the watchdog_device and
232 then use this function to set the user "preferred" timeout value.