linux-kernel - Re: [PATCH v2 2/4] gpiolib: Add ability to get GPIO pin direction

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Date:	Thu, 17 Feb 2011 12:00:43 +0100
From:	Wolfram Sang <w.sang@...gutronix.de>
To:	Peter Tyser <ptyser@...-inc.com>
Cc:	linux-kernel@...r.kernel.org, Alek Du <alek.du@...el.com>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	Eric Miao <eric.y.miao@...il.com>,
	Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Joe Perches <joe@...ches.com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH v2 2/4] gpiolib: Add ability to get GPIO pin direction

On Wed, Feb 16, 2011 at 06:56:54PM -0600, Peter Tyser wrote:
> Add a new get_direction() function to the gpio_chip structure.  This is
> useful so that the direction of a pin can be determined when its
> initially exported.  Previously, the direction defaulted to "unknown"
> regardless of the actual configuration of the GPIO pin.
> 
> If a GPIO driver implements get_direction(), it is called in
> gpio_request() to set the initial direction of the pin accurately.
> 
> Cc: Alek Du <alek.du@...el.com>
> Cc: Samuel Ortiz <sameo@...ux.intel.com>
> Cc: David Brownell <dbrownell@...rs.sourceforge.net>
> Cc: Eric Miao <eric.y.miao@...il.com>
> Cc: Uwe Kleine-K?nig <u.kleine-koenig@...gutronix.de>
> Cc: Mark Brown <broonie@...nsource.wolfsonmicro.com>
> Cc: Joe Perches <joe@...ches.com>
> Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
> Cc: Grant Likely <grant.likely@...retlab.ca>
> Signed-off-by: Peter Tyser <ptyser@...-inc.com>
> ---
> Changes since v1:
> - Add support for "unknown" direction
> 
>  drivers/gpio/gpiolib.c     |   20 ++++++++++++++++++++
>  include/asm-generic/gpio.h |    4 ++++
>  2 files changed, 24 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 0113c10..7723beb 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -1214,6 +1214,26 @@ int gpio_request(unsigned gpio, const char *label)
>  		}
>  	}
>  
> +	if (chip->get_direction) {
> +		/* chip->get_direction may sleep */
> +		spin_unlock_irqrestore(&gpio_lock, flags);
> +		switch (chip->get_direction(chip, gpio - chip->base)) {
> +		case -1:

Use some #defines instead of hardcoded values?

> +			clear_bit(FLAG_DIR_OUT, &desc->flags);
> +			clear_bit(FLAG_DIR_IN, &desc->flags);
> +			break;
> +		case 0:
> +			set_bit(FLAG_DIR_IN, &desc->flags);
> +			clear_bit(FLAG_DIR_OUT, &desc->flags);
> +			break;
> +		case 1:
> +			set_bit(FLAG_DIR_OUT, &desc->flags);
> +			clear_bit(FLAG_DIR_IN, &desc->flags);
> +			break;
> +		}
> +		spin_lock_irqsave(&gpio_lock, flags);

You are changing the flags without the lock. I think it would be good to copy
the locking-pattern of chip->request for now.

Regards,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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