linux-kernel - Re: [PATCH 1/2] gpiolib: introduce gpio_set

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Message-ID: <20111125145905.GA17151@legolas.emea.dhcp.ti.com>
Date:	Fri, 25 Nov 2011 16:59:06 +0200
From:	Felipe Balbi <balbi@...com>
To:	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
Cc:	Felipe Balbi <balbi@...com>, linux-kernel@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...el.com>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH 1/2] gpiolib: introduce gpio_set_pullup

On Fri, Nov 25, 2011 at 03:23:05PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> On 16:16 Fri 25 Nov     , Felipe Balbi wrote:
> > Hi,
> > 
> > On Fri, Nov 25, 2011 at 03:08:39PM +0100, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > > Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>
> > > Cc: Nicolas Ferre <nicolas.ferre@...el.com>
> > > Cc: Grant Likely <grant.likely@...retlab.ca>
> > > ---
> > >  drivers/gpio/gpiolib.c     |   44 ++++++++++++++++++++++++++++++++++++++++++++
> > >  include/asm-generic/gpio.h |    4 ++++
> > >  include/linux/gpio.h       |    5 +++++
> > >  3 files changed, 53 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > > index a971e3d..b7e5e75 100644
> > > --- a/drivers/gpio/gpiolib.c
> > > +++ b/drivers/gpio/gpiolib.c
> > > @@ -1519,6 +1519,50 @@ fail:
> > >  }
> > >  EXPORT_SYMBOL_GPL(gpio_set_debounce);
> > >  
> > > +/**
> > > + * gpio_set_pullup - sets @pullup for a @gpio
> > > + * @gpio: the gpio to set pullup
> > > + * @pullup: pullup level
> > > + */
> > > +int gpio_set_pullup(unsigned gpio, unsigned pullup)
> > > +{
> > > +	unsigned long		flags;
> > > +	struct gpio_chip	*chip;
> > > +	struct gpio_desc	*desc = &gpio_desc[gpio];
> > > +	int			status = -EINVAL;
> > > +
> > > +	spin_lock_irqsave(&gpio_lock, flags);
> > > +
> > > +	if (!gpio_is_valid(gpio))
> > > +		goto fail;
> > > +	chip = desc->chip;
> > > +	if (!chip || !chip->set_pullup)
> > > +		goto fail;
> > > +	gpio -= chip->base;
> > > +	if (gpio >= chip->ngpio)
> > > +		goto fail;
> > > +	status = gpio_ensure_requested(desc, gpio);
> > > +	if (status < 0)
> > > +		goto fail;
> > > +
> > > +	/* now we know the gpio is valid and chip won't vanish */
> > > +
> > > +	spin_unlock_irqrestore(&gpio_lock, flags);
> > > +
> > > +	might_sleep_if(chip->can_sleep);
> > > +
> > > +	return chip->set_pullup(chip, gpio, pullup);
> > > +
> > > +fail:
> > > +	spin_unlock_irqrestore(&gpio_lock, flags);
> > > +	if (status)
> > > +		pr_debug("%s: gpio-%d status %d\n",
> > > +			__func__, gpio, status);
> > > +
> > > +	return status;
> > > +}
> > > +EXPORT_SYMBOL_GPL(gpio_set_pullup);
> > 
> > Maybe I'm missing something, but isn't it essentially what
> > gpio_set_value() does ? I mean, you set a pullup and you get '1' value
> > and set a pulldown and you get a '0' value ??
> > 
> > Without a proper description of the necessity for this change, I can't
> > easily tell them apart :-(
> set_value is for output set_pullup is for input mode
> 
> some IP allow you when you configure an gpio as input to enable the
> internal pullup so no need on the board to add an external pull up

I see, that would fit nicely on the changelog :-)

-- 
balbi

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