linux-kernel - Re: [PATCH 1/2] x86, gpio: Increase ARCH_NR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 9 Sep 2014 09:24:59 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Alexandre Courbot <gnurou@...il.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Ning Li <ning.li@...el.com>, Alan Cox <alan@...ux.intel.com>,
	Mark Brown <broonie@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>
Subject: Re: [PATCH 1/2] x86, gpio: Increase ARCH_NR_GPIOs to 512

On Mon, Sep 8, 2014 at 1:47 PM, Mika Westerberg
<mika.westerberg@...ux.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@...ux.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.

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?

Yours,
Linus Walleij
--
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/