[PATCH 03/10] watchdog: Make stop function optional


Maxim Yu, Osipov
 

From: Guenter Roeck <linux@...>

Backport from kernel.org, upstream commit d0684c8a9354

Not all hardware watchdogs can be stopped. The driver for
such watchdogs would typically only set the WATCHDOG_HW_RUNNING
flag in its stop function. Make the stop function optional and set
WATCHDOG_HW_RUNNING in the watchdog core if it is not provided.

Signed-off-by: Guenter Roeck <linux@...>
Signed-off-by: Wim Van Sebroeck <wim@...>
[mosipov@... backported to 4.4.y]
Signed-off-by: Maxim Yu. Osipov <mosipov@...>
---
Documentation/watchdog/watchdog-kernel-api.txt | 20 ++++++++++++--------
drivers/watchdog/watchdog_core.c | 2 +-
drivers/watchdog/watchdog_dev.c | 6 +++++-
3 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
index b12789745f86..a376f281f5a7 100644
--- a/Documentation/watchdog/watchdog-kernel-api.txt
+++ b/Documentation/watchdog/watchdog-kernel-api.txt
@@ -85,7 +85,8 @@ It contains following fields:
If set, the infrastructure will send heartbeats to the watchdog driver
if 'timeout' is larger than max_hw_heartbeat_ms, unless WDOG_ACTIVE
is set and userspace failed to send a heartbeat for at least 'timeout'
- seconds.
+ seconds. max_hw_heartbeat_ms must be set if a driver does not implement
+ the stop function.
* bootstatus: status of the device after booting (reported with watchdog
WDIOF_* status bits).
* driver_data: a pointer to the drivers private data of a watchdog device.
@@ -141,17 +142,20 @@ are:
device.
The routine needs a pointer to the watchdog timer device structure as a
parameter. It returns zero on success or a negative errno code for failure.
-* stop: with this routine the watchdog timer device is being stopped.
- The routine needs a pointer to the watchdog timer device structure as a
- parameter. It returns zero on success or a negative errno code for failure.
- Some watchdog timer hardware can only be started and not be stopped.
- If a watchdog can not be stopped, the watchdog driver must set the
- WDOG_HW_RUNNING flag in its stop function to inform the watchdog core that
- the watchdog is still running.

Not all watchdog timer hardware supports the same functionality. That's why
all other routines/operations are optional. They only need to be provided if
they are supported. These optional routines/operations are:
+* stop: with this routine the watchdog timer device is being stopped.
+ The routine needs a pointer to the watchdog timer device structure as a
+ parameter. It returns zero on success or a negative errno code for failure.
+ Some watchdog timer hardware can only be started and not be stopped. A
+ driver supporting such hardware does not have to implement the stop routine.
+ If a driver has no stop function, the watchdog core will set WDOG_HW_RUNNING
+ and start calling the driver's keepalive pings function after the watchdog
+ device is closed.
+ If a watchdog driver does not implement the stop function, it must set
+ max_hw_heartbeat_ms.
* ping: this is the routine that sends a keepalive ping to the watchdog timer
hardware.
The routine needs a pointer to the watchdog timer device structure as a
diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
index 873f13972cf4..41f1854d026b 100644
--- a/drivers/watchdog/watchdog_core.c
+++ b/drivers/watchdog/watchdog_core.c
@@ -145,7 +145,7 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
return -EINVAL;

/* Mandatory operations need to be supported */
- if (wdd->ops->start == NULL || wdd->ops->stop == NULL)
+ if (!wdd->ops->start || (!wdd->ops->stop && !wdd->max_hw_heartbeat_ms))
return -EINVAL;

watchdog_check_min_max_timeout(wdd);
diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
index 55dc73f9b837..ca64724bf59a 100644
--- a/drivers/watchdog/watchdog_dev.c
+++ b/drivers/watchdog/watchdog_dev.c
@@ -237,7 +237,11 @@ static int watchdog_stop(struct watchdog_device *wdd)
goto out_stop;
}

- err = wdd->ops->stop(wdd);
+ if (wdd->ops->stop)
+ err = wdd->ops->stop(wdd);
+ else
+ set_bit(WDOG_HW_RUNNING, &wdd->status);
+
if (err == 0) {
clear_bit(WDOG_ACTIVE, &wdd->status);
watchdog_update_worker(wdd);
--
2.11.0

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