linux-kernel - Re: [PATCH] Input: pmic8xxx-pwrkey - Set sane default for debounce time

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Message-ID: <20140331182342.GD28265@joshc.qualcomm.com>
Date:	Mon, 31 Mar 2014 13:23:42 -0500
From:	Josh Cartwright <joshc@...eaurora.org>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-input@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] Input: pmic8xxx-pwrkey - Set sane default for debounce
 time

On Mon, Mar 31, 2014 at 11:14:24AM -0700, Stephen Boyd wrote:
> If the debounce time is 0 our usage of ilog2() later on in this
> driver will cause undefined behavior. If CONFIG_OF=n this fact is
> evident to the compiler, and it emits a call to ____ilog2_NaN()
> which doesn't exist. Fix this by setting a sane default for
> debounce.
> 
> Reported-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
> ---
>  drivers/input/misc/pmic8xxx-pwrkey.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/input/misc/pmic8xxx-pwrkey.c b/drivers/input/misc/pmic8xxx-pwrkey.c
> index 1cb8fda7a166..27add04676e1 100644
> --- a/drivers/input/misc/pmic8xxx-pwrkey.c
> +++ b/drivers/input/misc/pmic8xxx-pwrkey.c
> @@ -92,7 +92,7 @@ static int pmic8xxx_pwrkey_probe(struct platform_device *pdev)
>  	bool pull_up;
>  
>  	if (of_property_read_u32(pdev->dev.of_node, "debounce", &kpd_delay))
> -		kpd_delay = 0;
> +		kpd_delay = 15625;

Should "debounce" even be optional?  I'm wondering if we should just
make it required...

At the very least this default value should be documented in the DT
binding.

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