Re: driver copy_to_user

[Michael Blizek]

Hi!

On 16:18 Fri 17 Dec     , Hemanth Kumar wrote:
> Hi All,
> 
>           In my driver code I have interrupt which is exactly 1 sec(gps-pps),
>           I want the data to be copied (copy_to_user) to the user space 
> through read function,After the elapse of interrupt(1 sec gps-pps),how do I 
> instantiate read function after elapse interrupt,Can anybody please share 
> idea,
> 
> Regards

You cannot just call copy_to_user to dump your data somewhere to userspace.
First you need to some some kind of kernel-userspace interface, e.g. a
character device. The user space program could then open() it and do a
read() to wait for some data. On the kernel side, you have to define and
register a function, which gets called by the user space - in this case
the counterpart of read(). If this function gets called, a buffer will be
passed to you. You can then copy the data to this buffer with copy_to_user.
But do *not* call this function in a interrupt handler or anywhere else. It
*has* to be called inside your read() function or a function directly or
indirectly called by it. If you receive the data only in your interrupt
function, you may have to put the data in a queue which will then be read in
your the read() function.

        -Michi
-- 
programing a layer 3+4 network protocol for mesh networks
see http://michaelblizek.twilightparadox.com


--
To unsubscribe from this list: send an email with
"unsubscribe kernelnewbies" to ecar...@nl.linux.org
Please read the FAQ at http://kernelnewbies.org/FAQ