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

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Message-ID: <0D753D10438DA54287A00B027084269764CEEDAC85@AUSP01VMBX24.collaborationhost.net>
Date:	Tue, 1 Feb 2011 10:27:23 -0600
From:	H Hartley Sweeten <hartleys@...ionengravers.com>
To:	Wolfram Sang <w.sang@...gutronix.de>
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [leds-pca9532] Add gpio capability

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.

Regards,
Hartley
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