On 05/14/2015 04:56 AM, Andreas Werner wrote:
Hi, in the next few weeks I need to write a driver for a window wachtdog implemented in a CPLD. I have some questions about the design of the driver and the best way to write this driver to also be able to submit it. The triggering and configuration of the Watchdog is done by several GPIOs which are connected to the CPLD watchdog device. The correct GPIOs are configurable using the Device Tree. 1. Timeout The timeout values are defined in ms and start from 20ms to 2560ms. The timout is set by 3 GPIOs this means we have only 8 different timout values. It is also possible that a future Watchdog CPLD device does have different timeout values. Is it possible to set ms timeouts? It seems that the WDT API does only support a resolution of 1sec. One idea would be to use the API timeout as something like a timeout index to set the different values. Of course this needs to be documented. e.g. timeout (API) timeout in device 1 20ms 2 100ms 3 500ms ... ... 2. Upper/Lower Window There is currently no support for a windowed watchdog in the wdt core. The lower window can be activated by a gpio and its timeout is defined as "upper windows timeout/4" What is the best way to implement those additional settings? Adding additional ioctl or export these in sysfs? --
Sorry for the maybe dumb question, but what is a window watchdog, and what is the lower window timeout for (assuming the upper window timeout causes the watchdog to expire) ? Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
