On 10/24/2013 12:33 PM, Maxime Bizon wrote: > > On Thu, 2013-10-24 at 10:52 +0100, Grant Likely wrote: > >> At this point if the hardware exists then it should be described in DTB, >> even if it is merely compatible, reg, interrupts and maybe clocks > > if your driver does not use them, chances are you'll get them wrong. > >> properties. In many cases that is all that is required. It /is/ okay to >> amend a binding later and to use default values if the new properties >> aren't present. > > how do you handle the case of a wrong property, because you only wrote > hardware description and not the driver ? > >> hardware description when enabling previously unused peripherals, but it >> is absolutely not friendly to change a binding/driver in a what that fails on >> previously working DTB (with the caveat that if no one notices, it >> isn't breakage). > > ok then how do we solve that case: > > - Marvell SOC 1 is mainlined > - Marvell SOC 2 is mainlined > - Marvell SOC 'x' is mainlined > - "PIO" hw crypto driver is written, working for all SOCs > - [1 year] > - SOCs bindings are marked as stable > - [1 year] > - someone rewrite the driver of hw crypto to use DMA, existing binding > is not ok because clock 'foo' or interrupt 'bar', now required, are not > present. > > what is the process merge that driver ? > > if the answer is that you need to keep PIO mode in driver so that > existing DTBs still works with it, then this is just plain *wrong*. That situation describes enabling a new feature. New features aren't necessarily expected to work without revising the DT, e.g. adding new properties/entries to describe the additional clocks/DMA-channels/... that are required. In many cases, those additions can even be made in a backwards-compatible way. Compatibility means that we shouldn't break old functionality, not that we shouldn't augment the existing bindings. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
