On 05/29/2013 02:39 AM, Benoit Cousson wrote: > Hi Afzal, > > On 05/29/2013 10:06 AM, Mohammed, Afzal wrote: >> Hi Jon, >> >> On Wed, May 29, 2013 at 03:35:10, Stephen Warren wrote: >>> On 05/28/2013 03:25 PM, Jon Hunter wrote: >> >>>>> ti,am335x-timer (applicable to AM335x devices) >>>>> ti,am335x-timer-1ms (applicable to AM335x devices) >>>>> + "ti,am4372-timer-1ms", "ti,am335x-timer-1ms" for AM43x 1ms timer >>>>> + "ti,am4372-timer", "ti,am335x-timer" for AM43x timers other than 1ms one >> >>>> If you are adding more compatibility strings, then this implies that the >>>> AM43x timers are not 100% compatible with any other device listed (such >>>> as am335x or any omap device). That's fine but you should state that in >>>> the changelog. If the AM43x timer registers are 100% compatible with >>>> existing devices you should not add these. >>> >>> I'm not sure that's true; .dts files should always include a compatible >>> value that describes the most specific model of the HW, plus any >>> baseline compatible value that the HW is compatible with. This allows >>> any required quirks/fixes/... to be applied for the specific HW model >>> later even if nobody knows right now they'll be needed. Hence, defining >>> new compatible values doesn't necessarily mean incompatible HW. >> >> Stephen took words out of my finger ;) >> >> Some explanations,I don;t >> >> 1. first compatible should be exact device [A], followed by compatible >> model (if one) >> 2. Minor effort in getting DT right the first time may help prevent >> difficult effort later modifying it (if a necessity comes), considering >> the fact that DT sources has to move out of Kernel at some point of >> time. And DT is not supposed to be modified, which may cause difficulty >> for the users (I had been a minor victim of this during rebase). >> >> As we both were in GPMC land earlier, an example, >> >> If my memory is right, GPMC IP in am335x is rev 6, and IP has 8 chip >> select, but one is not pinned out. Now assume that same IP is integrated >> in another SoC (probably OMAP4 has rev 6). Here if we use same compatible >> for both, driver cannot handle it properly (w/o knowledge about platform). >> But if exact compatible is mentioned, without modifying DT (which should >> be considered as a firmware) just by modifying Kernel, deciding based on >> compatible would help achieve what is required. > > That's true for the DTS itself, but here your are changing the binding > documentation which is supposed to reflect the driver "interface" in the > Device Tree model description. > > Since the driver does not support any new compatible string, you should > not update the binding. I don't agree here; the DT binding should define all the required and/or allowed values that must/should/can be present in the DT - the entire legal schema. The set of all compatible values is included in that, irrespective of whether a particular value actually (currently) defines a different HW interface or not. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
