Messages in this thread | | | Date | Thu, 13 Mar 2008 19:17:47 -0700 | From | Andrew Morton <> | Subject | Re: [patch 2.6.25-rc5 1/2] gpiolib: dynamic gpio number allocation |
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On Thu, 13 Mar 2008 16:53:58 -0800 David Brownell <david-b@pacbell.net> wrote:
> On Thursday 13 March 2008, Andrew Morton wrote: > > On Thu, 13 Mar 2008 15:18:58 -0800 > > David Brownell <david-b@pacbell.net> wrote: > > > > > On Thursday 13 March 2008, Andrew Morton wrote: > > > > > > > hm. I suppose that if someone want a huge number of GPIOs then we can > > > > convert this to a bitmap or an IDR tree easily enough. > > > > > > 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.
Where did the CONFIG_NR_GPIOS discussion disappear to?
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