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

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Message-ID: <20160915181244.GI1811@lahna.fi.intel.com>
Date:   Thu, 15 Sep 2016 21:12:44 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        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

On Thu, Sep 15, 2016 at 05:07:58PM +0100, Marc Zyngier wrote:
> 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).

We can make drivers to allocate it and only if set use it in core.

> 
> > +	if (!chip->valid_mask)
> > +		return -ENOMEM;
> 
> You really want to revise your error handling here.

Oops, right. It should be:

	if (!chip->valid_mask) {
		status = -ENOMEM;
		goto err_remove_chip;
	}