linux-kernel - Re: [leds-pca9532] Add gpio capability

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Message-ID: <AANLkTi=PQzr+6FupmsgzJB3SKJiH83KV9WJu+D=g3rtV@mail.gmail.com>
Date:	Tue, 1 Feb 2011 18:22:20 +0100
From:	Joachim Eastwood <manabian@...il.com>
To:	H Hartley Sweeten <hartleys@...ionengravers.com>
Cc:	Wolfram Sang <w.sang@...gutronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [leds-pca9532] Add gpio capability

On 2/1/11, H Hartley Sweeten <hartleys@...ionengravers.com> wrote:
> On Tuesday, February 01, 2011 1:02 AM, Wolfram Sang wrote:
>>> From the datasheet:
>>>[...]
>>> So, you should provide both a direction_input and direction_output.
>>
>> He did in V2 of this patch (what made me also download the datasheet ;)).
>
> Ok.  Just looked at the v2 patch.
>
>> +static int pca9532_gpio_direction_input(struct gpio_chip *gc, unsigned
>> offset)
>> +{
>> + struct pca9532_data *data = container_of(gc, struct pca9532_data, gpio);
>> + struct pca9532_led *led = &data->leds[offset];
>> +
>> + /* To use as input ensure pin is not driven */
>> + led->state = PCA9532_OFF;
>> + pca9532_setled(led);
>> +
>> + return 0;
>> +}
>> +
>
> This looks good.  When configured as an input the pin needs to be set
> high-impedance,
> 00 which is PCA9532_OFF).
>
>> +static int pca9532_gpio_direction_output(struct gpio_chip *gc,
>> unsigned offset, int val)
>> +{
>> + return 0;
>> +}
>> +
>
> Not good.  When the pin is configured as an output, the direction_output
> method also
> requests that the pin be set to a desired level.  For this driver that means
> that the
> pca9532_gpio_direction_output function just needs to call
> pca9532_gpio_set_value.

ops, I overlooked the 'val' parameter in the direction_output
function.  I will create a v3.

Seems like I have been a bit careless with the direction setting... I
didn't really think through it since PCA9532 has no explicit direction
register.

Thanks for looking!

regards
Joachim Eastwood

> Regards,
> Hartley
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