linux-kernel - Re: [PATCH v3 1/4] gpiolib: Add "unknown" direction support

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Message-ID: <4D5DB833.4070902@bluewatersys.com>
Date:	Fri, 18 Feb 2011 13:07:15 +1300
From:	Ryan Mallon <ryan@...ewatersys.com>
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 v3 1/4] gpiolib: Add "unknown" direction support

On 02/18/2011 12:03 PM, Peter Tyser wrote:
> Previously, gpiolib would unconditionally flag all GPIO pins as inputs,
> regardless of their true state.  This resulted in all GPIO output pins
> initially being incorrectly identified as "input" in the GPIO sysfs.
> 
> Since the direction of GPIOs is not known prior to having their
> direction set, instead set the default direction to "unknown" to prevent
> user confusion.  A pin with an "unknown" direction can not be written or
> read via sysfs; it must first be configured as an input or output before
> it can be used.
> 
> While we're playing with the direction flag in/out defines, rename them to
> a more descriptive FLAG_DIR_* format.
> 
> 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>
> ---
> Change since V1:
> - This patch is new and is based on feedback from Alan to support a new
>   "unknown" direction.
> - Rename FLAG_IS_OUT to FLAG_DIR_OUT, and add FLAG_DIR_IN
> 
> Change since V2:
> - None
> 
>  drivers/gpio/gpiolib.c |   91 ++++++++++++++++++++++++++---------------------
>  1 files changed, 50 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index 649550e..eb74311 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -49,13 +49,14 @@ struct gpio_desc {
>  	unsigned long		flags;
>  /* flag symbols are bit numbers */
>  #define FLAG_REQUESTED	0
> -#define FLAG_IS_OUT	1
> -#define FLAG_RESERVED	2
> -#define FLAG_EXPORT	3	/* protected by sysfs_lock */
> -#define FLAG_SYSFS	4	/* exported via /sys/class/gpio/control */
> -#define FLAG_TRIG_FALL	5	/* trigger on falling edge */
> -#define FLAG_TRIG_RISE	6	/* trigger on rising edge */
> -#define FLAG_ACTIVE_LOW	7	/* sysfs value has active low */
> +#define FLAG_DIR_OUT	1	/* pin is an output */
> +#define FLAG_DIR_IN	2	/* pin is an input */
> +#define FLAG_RESERVED	3
> +#define FLAG_EXPORT	4	/* protected by sysfs_lock */
> +#define FLAG_SYSFS	5	/* exported via /sys/class/gpio/control */
> +#define FLAG_TRIG_FALL	6	/* trigger on falling edge */
> +#define FLAG_TRIG_RISE	7	/* trigger on rising edge */
> +#define FLAG_ACTIVE_LOW	8	/* sysfs value has active low */

This patch really shouldn't renumber all (and rename some) of the flags.
Patches should ideally do one thing only, so if you want to rename
FLAG_IS_OUT to FLAG_DIR_OUT that should be done in a separate patch.
Same goes for the renumbering, it should be a separate patch to adding
the support for "unknown" direction.

~Ryan

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