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

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Date:	Mon, 31 Mar 2014 11:29:27 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	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 03/31/14 11:23, Dmitry Torokhov wrote:
> 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;
> What if somebody supplied 0 via DT? Can we check and return -EINVAL?

Sure. Here's a v2.

-----8<------
From: Stephen Boyd <sboyd@...eaurora.org>
Subject: [PATCH v2] Input: pmic8xxx-pwrkey - Set sane default for debounce
 time

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 and failing to probe if debounce is 0 in the DT.

Reported-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Stephen Boyd <sboyd@...eaurora.org>
---
 drivers/input/misc/pmic8xxx-pwrkey.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/input/misc/pmic8xxx-pwrkey.c b/drivers/input/misc/pmic8xxx-pwrkey.c
index 1cb8fda7a166..3fb161902cc6 100644
--- a/drivers/input/misc/pmic8xxx-pwrkey.c
+++ b/drivers/input/misc/pmic8xxx-pwrkey.c
@@ -92,11 +92,11 @@ 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;
 
 	pull_up = of_property_read_bool(pdev->dev.of_node, "pull-up");
 
-	if (kpd_delay > 62500) {
+	if (kpd_delay > 62500 || kpd_delay == 0) {
 		dev_err(&pdev->dev, "invalid power key trigger delay\n");
 		return -EINVAL;
 	}

-- 
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