What are callback functions? How driver can initiate some message to userspace program?

Hi,

a rather simple question: COMEDI manual (drivers section) speaks about
some callback routines. What are they? In what they are different from
interrupt service routine that I can register? Can I use them to
communicate to user-space program (for example, to submit new data for
dislpaying and registration?).

And I am  interested in the following behaviour. The driver handles in
interrupt and can, meanwhile, check the condition for some registers
and remember their values in some buffer. How can I send these data to
program? The only thing that comes to my mind, invent "fake" CMD
handler that will return that data without processing commands to
device. So I call a command, its handler in driver reads private
driver's buffer and sends back (without actual device access). Or the
same to INSN. But instead, what would be the ways to communicate from
kernel space to user space, if my driver needs to deliver some data to
program? Just name the topic and I will look into it myself.

Thanks in advance, Askar

-- 
ICQ 19576333

Received on 2007-06-03Z16:12:57