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Date: Tue, 16 Sep 2014 12:34:31 +0300 From: Mika Westerberg <mika.westerberg@...ux.intel.com> To: Arnd Bergmann <arnd@...db.de> Cc: Linus Walleij <linus.walleij@...aro.org>, Alexandre Courbot <gnurou@...il.com>, Alan Cox <alan@...ux.intel.com>, Ning Li <ning.li@...el.com>, linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH v2 1/2] gpio: Increase ARCH_NR_GPIOs to 512 On Mon, Sep 15, 2014 at 06:50:34PM +0200, Arnd Bergmann wrote: > On Monday 15 September 2014, Mika Westerberg wrote: > > Some newer Intel SoCs, like Braswell already have more than 256 GPIOs > > available so the default limit is exceeded. Instead of adding more > > architecture specific gpio.h files with custom ARCH_NR_GPIOs we increase > > the gpiolib default limit to be twice the current. > > > > Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com> > > --- > > Changes to previous version is that now we increase the common limit > > instead of adding x86 specific gpio.h > > Can you please include the reasoning for this decision in the > changeset description? I'm sure you have your reasons, but from > the text above, it sounds like a rather bad idea. What other > architectures are impacted by this, and what is the kernel size > cost for it on those architectures? How about, Current generic ARCH_NR_GPIOS limit is 256 which starts to be too small for newer Intel SoCs like Braswell. In order to support GPIO controllers on these SoCs we increase ARCH_NR_GPIOS to be 512 which should be sufficient for now. The kernel size increases a bit with this change. Below is an example of x86_64 kernel image. ARCH_NR_GPIOS=256 text data bss dec hex filename 11476173 1971328 1265664 14713165 e0814d vmlinux ARCH_NR_GPIOS=512 text data bss dec hex filename 11476173 1971328 1269760 14717261 e0914d vmlinux So the BSS size and this the kernel image size increases by 4k. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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