Re: [PATCH 1/5] pinctrl: update the documentation for some pinconfig params
From: Heiko Stübner
Date: Sun Jun 16 2013 - 06:45:57 EST
Am Sonntag, 16. Juni 2013, 12:26:38 schrieb Linus Walleij:
> On Fri, Jun 14, 2013 at 5:42 PM, Heiko Stübner <heiko@xxxxxxxxx> wrote:
> > The BIAS_DISABLE and BIAS_HIGH_IMPEDANCE generic pinconfig options were
> > missing information about their argument - which should be ignored.
> > Also the BIAS_PULL_* options may have the pull strength as argument
> > when they are activated, while simpler hardware can use any
> > non-0 value for it.
> > Update the kerneldoc to reflect this.
> > Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx>
> I'm holding this patch off.
> > * @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.
> > + * impedance to VDD). If the argument is != 0 pull-up is enabled. On
> > + * hardware supporting this, the argument should contain the
> > strength of + * the pull in Ohm. If it is 0, pull-up is disabled.
> As noted by Laurent, a pull-up of 0 Ohm is a short-circuit (bascially the
> TOTAL pull-up) and it is pretty counter-intuitive to have that mean
> "disable pull-up". Can we avoid this?
> > * @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.
> > + * impedance to GROUND). If the argument is != 0 pull-down is
> > enabled. On + * hardware supporting this, the argument should
> > contain the strength of + * the pull in Ohm. If it is 0, pull-down
> > is disabled.
> > * @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. On hardware
> > supporting + * this, the argument should contain the strength of the
> > pull in Ohm. + * If it is 0, pull is disabled.
> Can't we rely on PIN_CONFIG_BIAS_DISABLE for all this?
you're the boss on this, I'll do whatever you say :-)
I was going after the existing documentation of "bias-pull-X = <0>" being
there to turn off this specific bias. So when reading the existing doc I was
assuming somebody had needed this in the past.
Actually I'm too more comfortable with only using bias-disable.
So I'll redo this patch to remove the disabling of a pull via this method, if
that's the right way to go.
Same with the rockchip driver.
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