linux-kernel - Re: [PATCH] gpiolib: implement dynamic base allocation

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Date:	Thu, 6 Mar 2008 04:02:24 +0300
From:	Anton Vorontsov <cbouatmailru@...il.com>
To:	David Brownell <david-b@...bell.net>
Cc:	Anton Vorontsov <avorontsov@...mvista.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] gpiolib: implement dynamic base allocation

On Wed, Mar 05, 2008 at 03:40:57PM -0800, David Brownell wrote:
> On Wednesday 05 March 2008, Andrew Morton wrote:
> > On Tue, 4 Mar 2008 20:03:07 +0300
> > Anton Vorontsov <avorontsov@...mvista.com> wrote:
> > 
> > > If gpio_chip->base is negative during registration, gpiolib requests
> > > dynamic base allocation. This is useful for devices being registered
> > > at run-time (in contrast to platform devices).
> > > 
> > > Signed-off-by: Anton Vorontsov <avorontsov@...mvista.com>
> > > ---
> > >  drivers/gpio/gpiolib.c |   42 ++++++++++++++++++++++++++++++++++++------
> > >  1 files changed, 36 insertions(+), 6 deletions(-)
> > > 
> > 
> > This conflicts in non-trivial ways with gpio-define-gpio_is_valid.patch. 
> > Could you please redo and retest against 2.6.25-rc3-mm1?

No problem, will rebase.

> And when you do that, could you make it assign GPIO numbers from
> the biggest number on down, instead of from the smallest on up?
> 
> Platforms normally assign those numbers from the bottom up ... so
> dynamic assignment should try to avoid reusing any numbers that may
> have been explicitly assigned, but not yet registered.  (Of course,
> if you can come up with a cleaner solution than that, it'd be great.
> Maybe platforms should also be able to mark ranges as "in use" as
> they start up, or something.)

Well, it is also trivial to implement gpiochip_reserve(start, end)
function that will mark reserved gpio->chip as ERR_PTR(-EACCESS),
and these ranges will be unavailable for the dynamic allocation.

Then, platforms could do gpiochip_reserve(0, GPIO_ARCH_END).
I think This is good solution from all and every POV, but this
needs a bit of platform code assistance.

What would you choice?

> And please add a pr_debug level message reporting dynamically
> assigned ranges.  That way, when problems crop up it'll be that
> much easier to notice what went wrong.

Will do.

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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