linux-kernel - Re: [PATCH v2 2/2] NFC: Add ACPI support for NXP PN544

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Date:	Thu, 12 Feb 2015 19:48:43 +0200
From:	Robert Dolca <robert.dolca@...el.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	linux-nfc@...1.01.org,
	Lauro Ramos Venancio <lauro.venancio@...nbossa.org>,
	Aloisio Almeida Jr <aloisio.almeida@...nbossa.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	Berg Johannes <johannes.berg@...el.com>,
	Clement Perrochaud <clement.perrochaud@....com>
Subject: Re: [PATCH v2 2/2] NFC: Add ACPI support for NXP PN544

Hi Uwe,

On Thu, Feb 12, 2015 at 09:14:59AM +0100, Uwe Kleine-König wrote:
> On Mon, Jan 26, 2015 at 01:13:37PM +0200, Robert Dolca wrote:
> > +	/* Get EN GPIO from ACPI */
> > +	gpiod_en = devm_gpiod_get_index(dev, PN544_GPIO_NAME_EN, 1);
> Actually devm_gpiod_get_index takes 4 arguments. In your case you should
> also pass GPIOD_OUT_LOW, then you can skip the gpiod_direction_output
> part below.
> 
> > +	if (IS_ERR(gpiod_en)) {
> > +		nfc_err(dev,
> > +			"Unable to get EN GPIO\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	phy->gpio_en  = desc_to_gpio(gpiod_en);
> Why don't you save a reference to the gpiod instead? Mixing usage of raw
> and gpiod might result in surprising results. For example
> 
> 	gpiod_direction_output(gpiod_en, 0);
> 
> might actually have the same result as
> 
> 	gpio_direction_output(gpio_en, 1);
> 
> if the matching gpio is marked as active low.
> 
> > +
> > +	/* Configuration EN GPIO */
> > +	ret = gpiod_direction_output(gpiod_en, 0);
> > +	if (ret) {
> > +		nfc_err(dev, "Fail EN pin direction\n");
> > +		return ret;
> > +	}
> > +
> > +	/* Get FW GPIO from ACPI */
> > +	gpiod_fw = devm_gpiod_get_index(dev, PN544_GPIO_NAME_FW, 2);
> > +	if (IS_ERR(gpiod_fw)) {
> > +		nfc_err(dev,
> > +			"Unable to get FW GPIO\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	phy->gpio_fw  = desc_to_gpio(gpiod_fw);
> > +
> > +	/* Configuration FW GPIO */
> > +	ret = gpiod_direction_output(gpiod_fw, 0);
> > +	if (ret) {
> > +		nfc_err(dev, "Fail FW pin direction\n");
> > +		return ret;
> > +	}
> The same comments apply here.
> 
> > +
> > +	/* Get IRQ GPIO */
> > +	gpiod_irq = devm_gpiod_get_index(dev, PN544_GPIO_NAME_IRQ, 0);
> > +	if (IS_ERR(gpiod_irq)) {
> > +		nfc_err(dev,
> > +			"Unable to get IRQ GPIO\n");
> > +		return -ENODEV;
> > +	}
> > +
> > +	phy->gpio_irq = desc_to_gpio(gpiod_irq);
> > +
> > +	/* Configure IRQ GPIO */
> > +	ret = gpiod_direction_input(gpiod_irq);
> > +	if (ret) {
> > +		nfc_err(dev, "Fail IRQ pin direction\n");
> > +		return ret;
> > +	}
> > +
> > +	/* Map the pin to an IRQ */
> > +	ret = gpiod_to_irq(gpiod_irq);
> > +	if (ret < 0) {
> > +		nfc_err(dev, "Fail pin IRQ mapping\n");
> > +		return ret;
> > +	}
> and here.

I didn't use gpiod_* functions because the existing enumeration method for
platform init and device tree was using gpio_* functions.

Also as far as I know the device tree implementation will not give you the
gpiod data structure. It gives you only the gpio index.

Keeping both gpiod and gpio depending on the enumeration method is unscallable
so I didn't choose that.

Regards,
Robert
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