On Wed, Jan 13, 2010 at 11:02 AM, Scott Wood <[email protected]> wrote: > Grant Likely wrote: >> It's not worth toying with. Just create a new compatible value for this >> new binding and be done with >> it. When a driver gets modified to handle the new behaviour, then it >> can be also changed to bind against the new compatible value too. > > I agree that a new compatible is warranted from a theoretical perspetive, > though from a practical compatibility perspective one should consider the > odds of something breaking because old code chokes on the new bits, versus > the old code not recognizing the new compatible and thus not binding the > device at all.
Letting old drivers bind against new bindings that aren't actually the same isn't good practice and leaves little recourse if we really do need to differentiate between them in the future. Teaching the current driver to match against the new value is a one line change. Choosing a new compatible value is so inexpensive, trivial, and safe that I think it is a no-brainer decision. > Is there any interest in standardizing this with a new compatible, or should > it be FSL-only? Instead of trying to come up with a new "generic/standard" compatible value, just adopt the name of the first part to use the new binding as the standard compatible value. If the binding catches on then great, new parts will just claim compatibility with the old. If it does not, then we won't have wasted time trying to predict the future and wrangling about what a so-called generic binding should look like. So, instead of trying to do something like the following for, say, a future 16 core version of the p4080: compatible = "fsl,p4160-mpic", 'open-pic-enhanced"; Do this instead: compatible = "fsl,p4160-mpic", "fsl,p4080-mpic" This also has the advantage of the meaning of a fsl,p4080-mpic compatible device is grounded in some real piece of hardware, not in something made up who's definition can change over time. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. _______________________________________________ devicetree-discuss mailing list [email protected] https://lists.ozlabs.org/listinfo/devicetree-discuss
