Hey Arnaud, On Mon, Apr 13, 2015 at 06:06:49PM +0200, Arnaud Ebalard wrote: > Jason Cooper <jason@xxxxxxxxxxxxxx> writes: ... > >> >> I really tried to adapt the existing driver to add the missing > >> >> features (especially the support for TDMA), but all my attempts > >> >> ended up introducing hackish code (not even talking about the > >> >> performance penalty of this approach). > >> > > >> > Ok, fair enough. It would be helpful if this account of attempting to > >> > reconcile the old driver made it into the commit message. This puts us > >> > in "perfect is the enemy of getting it done" territory. > >> > > >> >> I have another solution though: keep the existing driver for old > >> >> marvell SoCs (orion, kirkwood and dove), and add a new one for modern > >> >> SoCs (armada 370, XP, 375 and 38x), so that users of the mv_cesa driver > >> >> won't have to audit the new code. > >> > > >> > A fair proposal, but I'll freely admit the number of people actually auditing > >> > their code paths is orders of magnitude smaller than the number of users > >> > of the driver. > >> > > >> > There's such a large population of compatible legacy SoCs in the wild, > >> > adding an artificial boundary doesn't make sense. Especially since > >> > we're talking about features everyone would want to use. > >> > > >> > Perhaps we should keep both around, and deprecate the legacy driver over > >> > 3 to 4 cycles? > >> > >> But I guess that some users will want to use the new driver on the "old" marvell > >> SoCs (especially kirkwood and dove). > > > > Yes, despite my arguments, I'm one of those people. :-P > > > >> If we go to this path, then the best solution would be to still update > >> all the the dts, and modifying the old driver to be able to use the > >> new binding: for my point of view the only adaptation should be > >> related to the SRAM. It will be also needed to find a way to be able > >> to load only one driver at a time: either the old or the new, but not > >> both. > > The approach Boris proposed above seems to make everyone happy: > > 1) Keep the old driver for old marvells SoCs (kirkwood, dove and orion) > 2) Introduce the new driver for those that are not supported by the old > driver, i.e. armada (370, XP, 375, 38x) > > AFAICT, this can easily be done (based on compatible strings) and it > will let everyone the time to audit the new driver. Current users will > not be taken by surprise. At some point, when everyone is confident w/ > the new driver, we can then switch to that one for all SoCs so that > old platform get more performance. > > Additionnally, for those who want to get the feature of the new driver > for their old SoC right now, we *could* add a simple kernel config option > for the new driver to use it for the old SoC too (that one disabling the > old one). > > > > I'd appreciate if we'd look into it. I understand from on-list and > > off-list discussion that the rewrite was unavoidable. So I'm willing to > > concede that. Giving people time to migrate from old to new while still > > being able to update for other security fixes seems reasonable. > > Jason, what do you think of the approach above? I say keep it simple. We shouldn't use the DT changes to trigger one vice the other. We need to be able to build both, but only load one at a time. If that's anything other than simple to do, then we make it a Kconfig binary choice and move on. thx, Jason. -- 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
