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
[email protected]
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