locking a device for exclusive use by userspace process (or kernel thread)

[Greg KH]

On Wed, Mar 04, 2015 at 06:59:04PM +0100, Yann Droneaud wrote:
> Hi,
> 
> I have a device and I have to write a driver that exposes the
> following three operations to kernel modules AND to userspace
> programs:

<snip>

Why?  What type of device is this?  And who is asking you to do this
homework assignment?

good luck,

greg k-h