linux-kernel - Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)

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Date:	Tue, 3 Jun 2014 10:08:00 +0200
From:	Linus Walleij <linus.walleij@...aro.org>
To:	"Zhu, Lejun" <lejun.zhu@...ux.intel.com>
Cc:	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Alexandre Courbot <gnurou@...il.com>,
	Mathias Nyman <mathias.nyman@...ux.intel.com>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	jacob.jun.pan@...ux.intel.com, bin.yang@...el.com
Subject: Re: [PATCH v4] gpio: Add support for Intel SoC PMIC (Crystal Cove)

On Fri, May 30, 2014 at 4:12 AM, Zhu, Lejun <lejun.zhu@...ux.intel.com> wrote:

>         retval = gpiochip_add(&cg->chip);
>         if (retval) {
>                 dev_warn(&pdev->dev, "add gpio chip error: %d\n", retval);
>                 return ret;
>         }
>
>         gpiochip_irqchip_add(&cg->chip, &crystalcove_irqchip, 0,
>                              handle_simple_irq, IRQ_TYPE_NONE);
>
>         retval = request_threaded_irq(irq, NULL, crystalcove_gpio_irq_handler,
>                                       IRQF_ONESHOT, KBUILD_MODNAME, cg);

You should request the interrupt before you add the irqchip
I think. But it shouldn't really matter, mainly to avoid tearing
down the irqchip if getting the irq should fail.

> But this code will trigger a crash in gpiolib-acpi. Currently at the end
> of gpiochip_add(), it calls:
>
> gpiochip_add() -> acpi_gpiochip_add() -> acpi_gpiochip_request_interrupts()
>
> acpi_gpiochip_request_interrupts() needs ->to_irq to work. Without having
> called gpiochip_irqchip_add() already, this will be NULL:
>
>         if (!chip->to_irq)
>                 return;    <-- It will return here.
>
>         INIT_LIST_HEAD(&acpi_gpio->events);
>
> In the tear down path, acpi_gpiochip_free_interrupts() will find to_irq is
> no longer NULL, then it will walk an uninitialized list.
>
> So, should this be fixed in gpiolib-acpi?

Maybe, maybe in the drivers. I think Mika has a proposed solution...

Yours,
Linus Walleij
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