linux-kernel - Re: [PWM PATCH 1/7] API to consolidate PWM devices behind a common user and kernel interface

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Date:	Wed, 10 Feb 2010 07:55:04 -0600
From:	Bill Gatliff <bgat@...lgatliff.com>
To:	H Hartley Sweeten <hartleys@...ionengravers.com>
CC:	linux-embedded@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PWM PATCH 1/7] API to consolidate PWM devices behind a common
 user and kernel interface

H Hartley Sweeten wrote:
>> +int pwm_set_polarity(struct pwm_channel *p,
>> +		     int active_high)
>> +{
>> +	struct pwm_channel_config c = {
>> +		.config_mask = PWM_CONFIG_POLARITY,
>> +		.polarity = active_high,
>> +	};
>> +	return pwm_config(p, &c);
>> +}
>> +EXPORT_SYMBOL(pwm_set_polarity);
>>     
>
> Has the 'polarity' logic been verified?
>
> pwm_set_polarity takes an active high flag that is passed to pwm_config.
> A write to the sysfs 'polarity' file passes the value directly to pwm_config.
> A read from the sysfs 'polarity' file returns struct pwm_channel ->active_low.
>
> Seems like a mis-match in logic.
>   

It was.  And on top of that, none of the drivers were reflecting their
polarity in their pwm_channel structures.

I renamed the channel structure variable to active_high for consistency,
and updated each of the drivers to set that value consistent with their
actual polarities.

Very good catch.



b.g.

-- 
Bill Gatliff
Embedded systems training and consulting
http://billgatliff.com
bgat@...lgatliff.com

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