Re: [patch/rfc 2.6.19-rc5] arch-neutral GPIO calls

[Bill Gatliff]

David Brownell wrote:

> On Monday 13 November 2006 12:26 pm, Bill Gatliff wrote:
>
>  
>
> > > Nah; look at arch/arm/plat-omap/gpio.c and ignore the mess, but observe
> > > that what you see there is essentially a bunch of "gpio controller"
> > > classes using the ugly "switch(type)" dispatch scheme instead of the
> > > prettier "type->op()" dispatch scheme.  All that stuff needs to be
> > > cleaner, but for now it'd suffice to add a new FPGA typecode.
> > >      
> > Agreed.  But if we add to the machine descriptor, then not only do you 
> > not need to touch arch-omap/gpio.c, but you can take that switch 
> > statement out, too.  Just one less chunk of code to tweak when a new 
> > platform is supported.
> >    
>
> Do non-ARM platforms have board/machine descriptors on Linux, though?
> I thought most didn't ...
>  


PPC does.  See arch/ppc/platforms/chestnut.c:platform_init().

> One could come up with an implementation that uses GPIO numbers
> as indices into a descriptor array, and using board-specific
> initialization of that array ... just like with IRQs and irq_chip.
>
> That could lead to heavier weight implementations than I'd prefer
> to see (since GPIOs are a very light weight notion!), but it'd
> certainly provide a more reusable way to add GPIO controllers.
>
> All behind the API I proposed, note -- no changes needed.
>  


Indeed.  I'm all for lightweight, but especially for nice and neat code.


b.g.

--
Bill Gatliff
bgat@xxxxxxxxxxxxxxx

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