Messages in this thread | | | Date | Tue, 9 Sep 2014 12:46:44 +0300 | From | Mika Westerberg <> | Subject | Re: [PATCH 1/2] x86, gpio: Increase ARCH_NR_GPIOs to 512 |
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On Tue, Sep 09, 2014 at 09:24:59AM +0200, Linus Walleij wrote: > On Mon, Sep 8, 2014 at 1:47 PM, Mika Westerberg > <mika.westerberg@linux.intel.com> wrote: > > > Some newer Intel SoCs like Braswell already have more than 256 GPIOs > > available so the default limit is exceeded. In order to support these add > > back the custom GPIO header with limit of 512 GPIOs for x86. > > > > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> > > Argh! This is the kind of stuff I want to get rid of .... > > Preferably gpio should be a subsystem without a lot of hooks all over > the place with arch-specific modifications for this and that, including > the max number of GPIOs. > > I would actually prefer if you bump the value in > include/asm-generic/gpio.h to 512 over this.
OK, this makes sense and I can do the change for the next revision of the patch.
> But better still, now that we have descriptors etc would be to define > some new per-arch selectable config option like > CONFIG_ONLY_DYNAMIC_GPIO that changes the GPIO > core to use something like a radix tree to store and retrieve > descriptors. > > I.e. in drivers/gpio/gpiolib.c get rid of this: > static struct gpio_desc gpio_desc[ARCH_NR_GPIOS]; > > Replace it with a radix tree of descriptors. > > This however makes it *impossible* to use things like desc_to_gpio() > and/or gpio_to_desc() so the code has to be augmented all over the > place to avoid any uses of GPIO numbers on that architecture, > but I am sure it *can* be done on pure ACPI or device tree > systems, and that's what we should aim for. > > Comments?
That's a rather big rework to the GPIO subsystem and its users. I agree that it should be the goal eventually. For x86 such conversion is not that simple because we have systems out there that have neither ACPI nor DT available.
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