From: David Brownell <david-b@pacbell.net>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, avorontsov@ru.mvista.com
Subject: Re: [patch 2.6.25-rc5 1/2] gpiolib: dynamic gpio number allocation
Date: Thu, 13 Mar 2008 16:53:58 -0800 [thread overview]
Message-ID: <200803131753.58733.david-b@pacbell.net> (raw)
In-Reply-To: <20080313162803.ab8bfd4c.akpm@linux-foundation.org>
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?
- Dave
next prev parent reply other threads:[~2008-03-14 0:54 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-13 22:49 [patch 2.6.25-rc5 1/2] gpiolib: dynamic gpio number allocation David Brownell
2008-03-13 23:00 ` Andrew Morton
2008-03-13 23:18 ` David Brownell
2008-03-13 23:28 ` Andrew Morton
2008-03-13 23:54 ` Anton Vorontsov
2008-03-14 0:53 ` David Brownell [this message]
2008-03-14 2:17 ` Andrew Morton
2008-03-14 5:52 ` David Brownell
2008-03-14 1:54 ` David Brownell
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