How to send system events from driver to application layer?

Question

I'm writing a driver for a device with Windows Embedded Compact 7 OS, in which applications written in .NET 3.5 will be running. My requirement is that, I need to send some custom defined system events (for some conditions that occurred in the driver) to these applications so that the corresponding event handlers written in the application should be executed when an event is invoked.

So,

What should I do to invoke/raise such events?

Which function is to be used?

How do a system event differ from a message?

How to add Event handlers in a .NET application?

TIA.

Answer 1

Using the plain win32 API, I would create a named event (ie supply a name for CreateEvent()). This can be use across process boundaries, including across the kernel/userspace boundary. You would then simply use WaitForSingleObject() and related functions to check the event state.

If you have a stream driver, you can also call ReadFile() from the application and simply stall inside the according handler function of the driver. This makes it pretty easy to add data to the event, too. Further, it provides separation between different processes that access the driver, or even different instances within the same process. Compare this with the event above, which is effectively system-wide visible and can also be set by different processes, although you can restrict this to some extent.

Another alternative is to use window messages (PostMessage(), SendMessage() etc) which also work across process boundaries. I'm not sure if this works from the kernel though. These would then end up in the "normal" message queue of eg the applications main window or any other window you previously told the driver. Compared to the other two approaches, you need a window as target, so it only works one way, and you don't know where a message came from.