How to use a Linux "platform_driver"? - linux

Question

There is an embedded system, and it provides functions in a struct of platform_driver:
static struct platform_driver infinity_wdt_driver = {
.probe = infinity_wdt_probe,
.remove = infinity_wdt_remove,
.shutdown = infinity_wdt_shutdown,
.driver = {
.owner = THIS_MODULE,
.name = "infinity-wdt",
.of_match_table = ms_watchdog_of_match_table,
},
};
module_platform_driver(infinity_wdt_driver);
In the infinity_wdt_probe it calls devm_kzalloc and devm_ioremap_resource:
static int infinity_wdt_probe(struct platform_device *pdev) {
...
wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
...
wdt->reg_base = devm_ioremap_resource(&pdev->dev, res);
...
}
How shall I utilize this driver? Do I need to write some C code, or Linux provides some standard way through filesystem for controlling this?
In the filesystem there is a directory under /sys/bus/platform/drivers/infinity-wdt, but it contains only a few files:
# ls -l
total 0
lrwxrwxrwx 1 root root 0 Nov 16 20:23 1f006000.watchdog -> ../../../../devices/soc0/soc/1f006000.watchdog
--w------- 1 root root 4096 Nov 16 20:23 bind
--w------- 1 root root 4096 Nov 16 20:23 uevent
--w------- 1 root root 4096 Nov 16 20:23 unbind
Is it somehow possible to use the driver with this filesystem above?
Some extra info: 1f006000.watchdog is a symlink to a directory which contains these:
# ls -l
total 0
lrwxrwxrwx 1 root root 0 Nov 16 20:23 driver -> ../../../../bus/platform/drivers/infinity-wdt
-rw-r--r-- 1 root root 4096 Nov 16 20:23 driver_override
-r--r--r-- 1 root root 4096 Nov 16 20:23 modalias
lrwxrwxrwx 1 root root 0 Nov 16 20:23 of_node -> ../../../../firmware/devicetree/base/soc/watchdog
lrwxrwxrwx 1 root root 0 Nov 16 20:23 subsystem -> ../../../../bus/platform
-rw-r--r-- 1 root root 4096 Nov 16 20:23 uevent
This is the kernel log:
# cat /var/log/messages | grep -i watchdog
Jan 1 04:00:02 kernel: [WatchDog]infinity_wdt_probe
Jan 1 04:00:02 kernel: [WatchDog]infinity_wdt_set_heartbeat
Jan 1 04:00:04 kernel: [WatchDog]infinity_wdt_start
Jan 1 04:00:04 kernel: [WatchDog] infinity_wdt_ping tmr_margin=a ^M
Jan 1 04:00:04 kernel: watchdog: watchdog0: watchdog did not stop!
Jan 1 04:00:04 kernel: [WatchDog] infinity_wdt_ping tmr_margin=a ^M
Jan 1 04:00:04 kernel: [WatchDog]infinity_wdt_set_timeout=60
Jan 1 04:00:04 kernel: [WatchDog]infinity_wdt_set_timeout data=3c ^M
Jan 1 04:00:04 kernel: [WatchDog] infinity_wdt_ping tmr_margin=3c ^M
Jan 1 04:00:04 kernel: [WatchDog] infinity_wdt_ping tmr_margin=3c ^M
Nov 16 21:03:11 kernel: [WatchDog] infinity_wdt_ping tmr_margin=3c ^M
Nov 16 21:03:41 kernel: [WatchDog] infinity_wdt_ping tmr_margin=3c ^M

Answer 1

"Platform" driver means driver that doesn't fit into other standard subsystem (e.g. USB, I2C, etc). In this case it's a watchdog driver, which is apparently supposed to reboot embedded system if it's not responsive.
Entries in sysfs are standard bookkeeping entries, automatically created for any driver by kernel.
Since driver contains "of_match_table", it implies that it must be correctly specified in the device tree. Given it generally works and has no other explicit interfaces (e.g. procfs, sysfs), this should be enough to enable it.
You might also check if corresponding /dev/watchdog* is created by this driver. If so, standard userspace watchdog can be used by specified this /dev/watchdog* file in its config file.