Subject: Platform data from devicetree

From: [email-masked] (Tony Prisk)
Date: Thu, 09 Aug 2012 12:35:11 +1200

On Wed, 2012-08-08 at 18:23 -0500, Rob Herring wrote:
> On 08/08/2012 06:06 PM, Tony Prisk wrote:
> > Quick question regarding platform_devices created from devicetree.
> > 
> > At the moment, we do a of_match_device() against vt8500_gpio_dt_ids[] to
> > get an of_device_id that contains the .data field to pass into the
> > driver.
> > 
> > Given that pdev is created from a match against vt8500_gpio_dt_ids[] as
> > well, why does pdev->dev.of_node.data == NULL? Is this data not
> > populated into this field? What data can be passed into this field?
> > 
> 
> This commit may be why:
> 
> commit b1608d69cb804e414d0887140ba08a9398e4e638
> Author: Grant Likely <[email-masked]>
> Date:   Wed May 18 11:19:24 2011 -0600
> 
>     drivercore: revert addition of of_match to struct device
> 
>     Commit b826291c, "drivercore/dt: add a match table pointer to struct
>     device" added an of_match pointer to struct device to cache the
>     of_match_table entry discovered at driver match time.  This was unsafe
>     because matching is not an atomic operation with probing a driver.  If
>     two or more drivers are attempted to be matched to a driver at the
>     same time, then the cached matching entry pointer could get
>     overwritten.
> 
>     This patch reverts the of_match cache pointer and reworks all users to
>     call of_match_device() directly instead.
> 
>     Signed-off-by: Grant Likely <[email-masked]>
> 
> 
> 
> > Regards
> > 
> > Tony Prisk
> > 
> > 
> > Example code below:
> > 
> > static struct of_device_id vt8500_gpio_dt_ids[] = {
> > 	{ .compatible = "via,vt8500-gpio", .data = &vt8500_data, },
> > 	{ .compatible = "wm,wm8505-gpio", .data = &wm8505_data, },
> > 	{ .compatible = "wm,wm8650-gpio", .data = &wm8650_data, },
> > 	{ /* Sentinel */ },
> > };
> > 
> > static int __devinit vt8500_gpio_probe(struct platform_device *pdev)
> > {
> > 	void __iomem *gpio_base;
> > 	struct device_node *np;
> > 	const struct of_device_id *of_id =
> > 			of_match_device(vt8500_gpio_dt_ids, &pdev->dev);
> > 
> > 	if (!of_id) {
> > 		dev_err(&pdev->dev, "Failed to find gpio controller\n");
> > 		return -ENODEV;
> > 	}
> > 
> > 	np = pdev->dev.of_node;
> > 	...
> > }
> > 
> > static struct platform_driver vt8500_gpio_driver = {
> > 	.probe		= vt8500_gpio_probe,
> > 	.driver		= {
> > 		.name	= "vt8500-gpio",
> > 		.owner	= THIS_MODULE,
> > 		.of_match_table = vt8500_gpio_dt_ids,
> > 	},
> > };
> > 
> > 
> > _______________________________________________
> > linux-arm-kernel mailing list
> > linux-arm-kernel at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> > 
> 

Thanks Rob.

Thought I was doing something wrong because it seemed like it should
work.