[dm-devel] communication between a dm target and a userspace application

[HyoGi Sim]

Hi,

I'm working with a dm device which needs a way to communicate with a
userspace application as follows:

1. The application gives a list of sectors which should be updated in
an async way by the dm device.
2. The application requests to the dm device a list of sectors which
meet with some condition.

What is a good way to implement this?
I'm rather new to the kernel as well as device mapper, and possible
ways that I can imagine are:

1. adding ioctl (is it possible/ok to have target specific ioctl command?)
2. creating a sysfs/proc entry

Or do you think it's a bad idea that the userspace application and the
dm device communicate in that way?

Thanks,
Hyogi