linux-kernel - Re: [PATCH v2 5/7] [PATCH 5/8] can: SJA1000 generic platform bus driver

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Message-ID: <20090513160235.5d2d281c@bike.lwn.net>
Date:	Wed, 13 May 2009 16:02:35 -0600
From:	Jonathan Corbet <corbet@....net>
To:	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Wolfgang Grandegger <wg@...ndegger.com>,
	Marc Kleine-Budde <mkl@...gutronix.de>,
	Oliver Hartkopp <oliver.hartkopp@...kswagen.de>
Subject: Re: [PATCH v2 5/7] [PATCH 5/8] can: SJA1000 generic platform bus
 driver

On Tue, 12 May 2009 11:28:02 +0200
Wolfgang Grandegger <wg@...ndegger.com> wrote:

> This driver adds support for the SJA1000 chips connected to the
> "platform bus", which can be found on various embedded systems.

[...]

> +
> +static u8 sp_read_reg(const struct net_device *dev, int reg)
> +{
> +	return ioread8((void __iomem *)(dev->base_addr + reg));
> +}
> +
> +static void sp_write_reg(const struct net_device *dev, int reg, u8 val)
> +{
> +	iowrite8(val, (void __iomem *)(dev->base_addr + reg));
> +}

So there's no locking around accesses to the hardware at all.  How do you
protect against concurrent access?

[...]

> +static int sp_remove(struct platform_device *pdev)
> +{
> +	struct net_device *dev = dev_get_drvdata(&pdev->dev);
> +	struct resource *res;
> +
> +	unregister_sja1000dev(dev);
> +	dev_set_drvdata(&pdev->dev, NULL);
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	release_mem_region(res->start, res->end - res->start + 1);
> +
> +	if (dev->base_addr)
> +		iounmap((void __iomem *)dev->base_addr);

Seems like you should unmap it before releasing it back to the kernel.
Nobody else is ever going to jump in and try to map it, but still...

> +	free_sja1000dev(dev);
> +
> +	return 0;
> +}

jon
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