Jan Kiszka wrote: > Gilles Chanteperdrix wrote: >> 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? > > Right now this sounds like a plan - but I don't feel 100% comfortable to > predict that we will get along with it. Converting some skin-specific > service to a generic one involves quite a lot of refactoring. It is not > really unlikely that we define some ABI now that will later turn out to > be insufficient for what we want to achieve.
For the posix skin, I can live with a two hops solution right now, and implement the one-hop solution later. user-space fd | | core skin fd table v kernel-space fd | | posix skin registry v actual object If we do this, there is not much re-factoring involved. The question really boils down to whether you accept this solution for the rtdm skin too. -- Gilles. _______________________________________________ Xenomai-core mailing list Xenomai-core@gna.org https://mail.gna.org/listinfo/xenomai-core