From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4AC61F57.2010404@domain.hid> Date: Fri, 02 Oct 2009 17:42:15 +0200 From: Gilles Chanteperdrix MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: [Xenomai-core] RTDM fd support. List-Id: Xenomai life and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: Xenomai core Hi Jan, from discussions on the mailing list, it seems that we are going to need that unified file descriptors thing. However, since everybody wants 2.5.0 to be released ASAP, we should try to think about any changes for this support which would break the ABI, do them now, and keep the rest for later. One such problem is the translation which currently exists between rtdm file descriptors and descriptors passed to the posix skin, by adding 1024 - 128. So, I propose to fix this issue. The idea Philippe had, and which I tend to agree to, was, in case of open/socket/accept, to open("/dev/null"), and use an association table somewhere to associate with the kernel-space descriptor number. Since we are at it, this association table could in fact be the file descriptor table, which we would put in the core skin ppd. The actual data structure should be sparse, a linked list does not scale, so, probably a hash would do. (I could also propose a solution based on avl trees, but their implementation is not nearly as simple). Additionnally, this would allow our open/socket to conform to posix which states that open should return the lowest free file descriptor. Should I propose a patch in that direction? Do you see any other possible cause of ABI breakage when we migrate to an unified file descriptors structure? TIA, regards. -- Gilles.