linux-kernel - Re: [PATCH] pinctrl: establish pull-up/pull-down terminology

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Date:	Mon, 17 Jun 2013 04:53:37 +0200
From:	Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:	Linus Walleij <linus.walleij@...ricsson.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Stephen Warren <swarren@...dia.com>,
	Anmar Oueja <anmar.oueja@...aro.org>,
	Linus Walleij <linus.walleij@...aro.org>,
	Heiko St�bner <heiko@...ech.de>,
	James Hogan <james.hogan@...tec.com>
Subject: Re: [PATCH] pinctrl: establish pull-up/pull-down terminology

Hi Linus,

On Sunday 16 June 2013 12:45:48 Linus Walleij wrote:
> From: Linus Walleij <linus.walleij@...aro.org>
> 
> It is counter-intuitive to have "0" mean disable in a boolean
> manner for electronic properties of pins such as pull-up and
> pull-down. Therefore, define that a pull-up/pull-down argument
> of 0 to such a generic option means that the pin is
> short-circuited to VDD or GROUND. Pull disablement shall be
> done using PIN_CONFIG_BIAS_DISABLE.
> 
> Cc: Heiko St�bner <heiko@...ech.de>
> Cc: James Hogan <james.hogan@...tec.com>
> Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Linus Walleij <linus.walleij@...aro.org>

Nice clarification, thank you.

Acked-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

(with one small comment below)

> ---
>  include/linux/pinctrl/pinconf-generic.h | 13 +++++++------
>  1 file changed, 7 insertions(+), 6 deletions(-)
> 
> diff --git a/include/linux/pinctrl/pinconf-generic.h
> b/include/linux/pinctrl/pinconf-generic.h index d414a77..67780f5 100644
> --- a/include/linux/pinctrl/pinconf-generic.h
> +++ b/include/linux/pinctrl/pinconf-generic.h
> @@ -36,14 +36,15 @@
>   *	tristate. The argument is ignored.
>   * @PIN_CONFIG_BIAS_PULL_UP: the pin will be pulled up (usually with high
>   *	impedance to VDD). If the argument is != 0 pull-up is enabled,
> - *	if it is 0, pull-up is disabled.
> + *	if it is 0, pull-up it total, i.e. the pin is connected to VDD.
>   * @PIN_CONFIG_BIAS_PULL_DOWN: the pin will be pulled down (usually with
> high *	impedance to GROUND). If the argument is != 0 pull-down is enabled,
> - *	if it is 0, pull-down is disabled.
> + *	if it is 0, pull-down is total, i.e. the pin is connected to GROUND.
>   * @PIN_CONFIG_BIAS_PULL_PIN_DEFAULT: the pin will be pulled up or down
> based *	on embedded knowledge of the controller, like current mux function.
> - *	If the argument is != 0 pull up/down is enabled, if it is 0,
> - *	the pull is disabled.
> + *	If the argument is != 0 pull up/down is enabled, if it is 0, the
> + *	configuration is ignored. The proper way to disable it is to use
> + *	@PIN_CONFIG_BIAS_DISABLE.
>   * @PIN_CONFIG_DRIVE_PUSH_PULL: the pin will be driven actively high and
>   *	low, this is the most typical case and is typically achieved with two
>   *	active transistors on the output. Setting this config will enable
> @@ -72,8 +73,8 @@
>   *	supplies, the argument to this parameter (on a custom format) tells
>   *	the driver which alternative power source to use.
>   * @PIN_CONFIG_SLEW_RATE: if the pin can select slew rate, the argument to
> - * 	this parameter (on a custom format) tells the driver which 
alternative
> - * 	slew rate to use.
> + *	this parameter (on a custom format) tells the driver which 
alternative
> + *	slew rate to use.

This hunk doesn't seem to belong to the patch.

>   * @PIN_CONFIG_LOW_POWER_MODE: this will configure the pin for low power
>   *	operation, if several modes of operation are supported these can be
>   *	passed in the argument on a custom form, else just use argument 1
-- 
Regards,

Laurent Pinchart

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