On Wed, Feb 26, 2014 at 04:50:46PM +0000, Alexander Shiyan wrote: > Hello. > > Среда, 26 февраля 2014, 16:00 UTC от Mark Rutland <mark.rutland@xxxxxxx>: > > On Tue, Feb 25, 2014 at 03:50:32PM +0000, Arnd Bergmann wrote: > > > On Tuesday 25 February 2014 19:47:57 Alexander Shiyan wrote: > > > > Вторник, 25 февраля 2014, 16:33 +01:00 от Arnd Bergmann <arnd@xxxxxxxx>: > > > > > On Tuesday 25 February 2014 19:27:47 Alexander Shiyan wrote: > > > => > > > > > > We really want to avoid wildcards in compatible strings. Can you call this > > > > > "cirrus,cs89712-pwm" to match the first SoC that came with this hardware? > > > > > Obviously if there was some chip before that (I'm not familiar with the > > > > > model numbers), use that instead. > > > > > > > > > > You can either list all chips you know that have this in the driver, > > > > > or you use "cirrus,cs89712-pwm" as the fallback, and use the name of > > > > > the SoC you have as the more specific string. > > > > > > > > It seems that in this case we will need to modify the compatibility string > > > > for other drivers that are already available in the kernel... > > > > > > Ah, right. I missed the binding for gpio and serial going in. > > > > > > DT maintainers, any suggestion on how we should proceed here? > > > > > > AFAICT, clps711x platform support is still work-in-progress, so we don't > > > have any upstream users to worry about yet, but changing them is still > > > going to be slightly messy. > > > > When allocating any new compatible strings, as Arnd says, we should > > avoid wildcards as they're usually far too encompassing and end up > > causing more trouble than they're worth. > > > > In this case how problematic are the wildcard strings? > > > > I assume we still have specific strings earlier in any compatible list > > in any case? If not, and there are possible differences, that should be > > fixed right away. > > > > We have a few options: > > > > a) Update the docs only. > > > > Note in the docs that "cirrus,clps711x-$UNIT" means anything > > compatible with the $UNIT in the cs89712. This may be > > counter-intuitive, and if a new clps711x platform comes out with an > > incompatible $UNIT it should omit "cirrus,clps711x-$UNIT" from its > > compatible list, but otherwise no harm done. > > > > b) Deprecate the existing string. > > > > Add "cirrus,cs89712-$UNIT" to the binding docs and driver. Mark > > "cirrus,clps711x-$UNIT" as deprecated in the binding document. > > Replace "cirrus,clps711x-$UNIT" with "cirrus,cs89712-$UNIT" in all > > DTs. > > > > This will mean new DTBs won't work with an older kernel, but as > > support is a work in progress that might not matter. Old DTBs will > > continue to function. > > > > Iff you can guarantee that the old string is not possibly being used > > by anyone, it can be dropped from the driver. If not it has to remain > > (though can be commented to be deprecated), so that old DTBs > > function. It's probably best to leave it there. > > > > c) Deprecate, maintaining (forwards) compatibility. > > > > As above, but rather than replacing "cirrus,clps711x-$UNIT" with > > "cirrus,cs89712-$UNIT" in DTs, place "cirrus,cs89712-$UNIT" before > > "cirrus,clps711x-$UNIT" in DTs. This allows new DTBs to work with > > older kernels too. Depending on what level of support you have in > > mainline currently this may or may not be an important consideration. > > If I understood correctly, in the variant "a", we change nothing. > Ie compatibility string is a global to entire platform, and in case of any > CPU differences, we simply add the additional compatibility string fully > meets the CPU name, for example for Cirrus Logic EP7312 this will be > like: "cirrus,ep7312-hw", "cirrus,clps711x-hw". > Correct? That depends. Option a still requires that we give a definite meaning to "cirrus,clps711x-$UNIT" to mean compatible with the unit on the cs89712. If a new unit is compatible with this, then it can have "cirrus,clps711x-$UNIT" as a fallback in its compatible list. If a new unit is not compatible and must be handled differently, then it should not have "cirrus,clps711x-$UNIT" in its compatible list. The naming you suggest for "cirrus,ep7312-$UNIT" seems sensible in either case. Cheers, Mark. -- 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
