On Sat, 20 Nov 2010 08:23 -0500, "Matt Shaver" <[email protected]> wrote: > On Fri, 19 Nov 2010 22:06:44 -0700 > Sebastian Kuzminsky <[email protected]> wrote: > > > rtapi_data has a cool feature: it has a "revision code" integer > > inside it, and all users of this shared memory verify that they are > > using the same revision of the struct as everyone else before they'll > > touch it[1]. I guess this is handy when you have out-of-tree rtapi > > modules and forget to recompile them when someone changes > > rtapi_data_t. I can't think of another use for it... > > I _think_ the purpose of this goes back to EMC's multi-computer roots. > The idea was _probably_ to ensure that if computer A made a connection > through NML (or maybe a shared memory bus?) to computer B, and tried to > manipulate the struct, both computers would have the same opinion of > what the struct looks like. > > There used to be quite a large number of PLATs or platforms (different > CPU architectures and OSs - do a 'grep PLAT *' in src/emc/usr_intf to > see the remnants of this) for which EMC and RCSLIB could be built, so it > would have been a bigger problem (out of sync code revisions) back then.
The feature in question is part of RTAPI, not NML or RCSLIB. RTAPI is much newer, dating back to about 2003 or so, when we wanted to get rid of all the #ifdefs dealing with operating systems and such in the realtime code. John Kasunich -- John Kasunich [email protected] ------------------------------------------------------------------------------ Beautiful is writing same markup. Internet Explorer 9 supports standards for HTML5, CSS3, SVG 1.1, ECMAScript5, and DOM L2 & L3. Spend less time writing and rewriting code and more time creating great experiences on the web. Be a part of the beta today http://p.sf.net/sfu/msIE9-sfdev2dev _______________________________________________ Emc-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-developers
