linux-kernel - Re: [PATCH 1/2] gpiolib: Add possibility to mask which GPIOs are added to IRQ domain

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Message-ID: <57DAC75E.5080203@arm.com>
Date:   Thu, 15 Sep 2016 17:07:58 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Phidias Chiang <phidias.chiang@...onical.com>,
        Anisse Astier <anisse@...ier.eu>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Yu C Chen <yu.c.chen@...el.com>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] gpiolib: Add possibility to mask which GPIOs are
 added to IRQ domain

Mika,

On 15/09/16 16:52, Mika Westerberg wrote:
> When using GPIO irqchip helpers to setup irqchip for a gpiolib based
> driver, it is not possible to select which GPIOs to add to the IRQ domain.
> Instead it just adds all GPIOs which is not always desired. For example
> there might be GPIOs that for some reason just cannot be used as interrupts
> at all.
> 
> To make this possible we add valid_mask to each gpio_chip and by default
> assume all GPIOs can be used as interrupts. Drivers can then tune this
> using clear_bit() or similar before they call gpiochip_irqchip_add().
> 
> Suggested-by: Linus Walleij <linus.walleij@...aro.org>
> Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
> ---
>  drivers/gpio/gpiolib.c      | 32 +++++++++++++++++++++++++++++---
>  include/linux/gpio/driver.h |  1 +
>  2 files changed, 30 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 53ff25ac66d8..d84c23b47f44 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1186,6 +1186,18 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data)
>  		if (status)
>  			goto err_remove_chip;
>  	}
> +
> +#ifdef CONFIG_GPIOLIB_IRQCHIP
> +	chip->valid_mask = kcalloc(BITS_TO_LONGS(chip->ngpio), sizeof(long),
> +				   GFP_KERNEL);

Do we really want to make this a mandatory thing? In most cases, I'd
expect this valid_mask to have all bits set, so you might as well not
allocate it at all in that case (and only allocate it if you actually
need it).

> +	if (!chip->valid_mask)
> +		return -ENOMEM;

You really want to revise your error handling here.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...