Re: [Xenomai] Reworking file descriptors

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On 12/15/2013 09:22 PM, Gilles Chanteperdrix wrote:
> 
> Hi Jan,
> 
> I have starting reworking the posix skin on forge to use the cobalt
> registry instead of the ad-hoc registry it currently uses. The next step
> for that work is to convert the file descriptors, offering a unified
> access with select to posix skin message queues and rtdm drivers, and
> working correctly with fork().
> 
> I have a clear idea on how I would do it for the posix message queues
> only. Just as I did for the semaphores, I would implement a hash table,
> where the file descriptor structures are indexed by the user-space file
> descriptor (obtained with open(/dev/null) for instance, so that xenomai
> file descriptors follow the posix specification, and use the smallest
> available descriptor), and the mm structure.
> 
> However, RTDM allows opening file descriptors in kernel-space, so it
> would break my implementation, because we can use NULL or &init_mm as
> the mm key, but what would we use as the file descriptor index?

Crazy ideas include calling xnregistry_enter and using the returned
handler as file descriptor in kernel-space, but that would give a
different way to get the file descriptor structure for kernel-space and
user-space.


-- 
                                                                Gilles.