Messages in this thread | | | From | David Brownell <> | Subject | Re: [patch 2.6.25-rc5 1/2] gpiolib: dynamic gpio number allocation | Date | Thu, 13 Mar 2008 21:52:57 -0800 |
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On Thursday 13 March 2008, Andrew Morton wrote: > > > > Actually, I tried IDRs for a while and they broke platforms > > > > which needed to initialize and use GPIOs early: before kmalloc > > > > would work. A real PITA that was -- and slow too. > > > > > > If IDRs were slow, that linear search will be glacial. > > > > The slowness of IDRs was needing to use them for the > > routine lookups ... versus the current array index, > > which costs a fraction of an instruction cycle and > > doesn't need separate locks. > > > > Or were you implying they should be used for something > > other than mapping GPIO numbers to controllers/state? > > For dynamic allocation. There should be no need for lookups outside > register/unregister.
So -- a secondary data structure used only for allocation? With the primary one as it is now?
If allocation were a hotspot something like that might be worth considering ... though such duplication is usually error prone. But it's not; such allocation is a rarity.
> Where did the CONFIG_NR_GPIOS discussion disappear to?
http://marc.info/?l=linux-kernel&m=120545979527097&w=2
I could maybe see a CONFIG_NR_EXTRA_GPIOS.
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