linux-kernel - Re: [PATCH v6 1/2] Ethernet driver for the WIZnet W5300 chip

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Message-ID: <20120403133619.GA3960@sirena.org.uk>
Date:	Tue, 3 Apr 2012 14:36:19 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Mike Sinkovsky <msink@...monline.ru>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 1/2] Ethernet driver for the WIZnet W5300 chip

On Tue, Apr 03, 2012 at 04:58:45PM +0600, Mike Sinkovsky wrote:

> +static irqreturn_t w5300_detect_link(int irq, void *ndev_instance)
> +{
> +	struct net_device *ndev = ndev_instance;
> +	struct w5300_priv *priv = netdev_priv(ndev);
> +
> +	if (netif_running(ndev)) {
> +		if (gpio_get_value(priv->link_gpio) != 0) {
> +			netif_info(priv, link, ndev, "link is up\n");
> +			netif_carrier_on(ndev);
> +		} else {
> +			netif_info(priv, link, ndev, "link is down\n");
> +			netif_carrier_off(ndev);
> +		}
> +	}
> +
> +	return IRQ_HANDLED;
> +}

This relies on ndev being valid and on the gpio being requested but...

> +	priv->link_gpio = data->link_gpio;
> +	if (gpio_is_valid(priv->link_gpio)) {
> +		char *link_name = devm_kzalloc(&pdev->dev, 16, GFP_KERNEL);
> +		if (!link_name)
> +			return -ENOMEM;
> +		snprintf(link_name, 16, "%s-link", name);
> +		priv->link_irq = gpio_to_irq(priv->link_gpio);
> +		if (devm_request_threaded_irq(&pdev->dev,
> +				priv->link_irq, NULL, w5300_detect_link,
> +				IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING,
> +				link_name, priv->ndev) < 0)
> +			priv->link_gpio = -EINVAL;
> +	}

...you use devm_request_threaded_irq() here and rely on it for cleanup.
Are you sure there's no possibility of the interrupt firing after you
start to tear down the device?

By using a specifically threaded IRQ you're also adding a performance
overhead for no good reason if you can call netdev_carrier_*() from IRQ
context and the GPIO is capable of generating a hard IRQ.  If you use
request_any_context_irq() instead then the driver will get a hard IRQ if
that's supported.
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