Re: Using statically allocated memory for platform_data.

From: Uwe Kleine-König
Date: Mon Nov 02 2009 - 05:39:51 EST


On Mon, Nov 02, 2009 at 11:23:16AM +0100, Antonio Ospite wrote:
> Hi,
> I noted that in some mfd drivers (drivers/mfd/ezx-pcap.c and
> drivers/mfd/da903x.c) there is code like this:
> static int __devinit pcap_add_subdev(struct pcap_chip *pcap,
> struct pcap_subdev *subdev)
> {
> struct platform_device *pdev;
> pdev = platform_device_alloc(subdev->name, subdev->id);
> pdev->dev.parent = &pcap->spi->dev;
> pdev->dev.platform_data = subdev->platform_data;
> return platform_device_add(pdev);
> }
> Note the _direct_assignment_ of platform data; then in board init code
> there are often global struct pointers passed as subdev platform data,
> see arch/arm/mach-pxa/em-x270.c::em_x270_da9030_subdevs for instance.
> In these cases, whenever the subdev platform device is unregistered,
> the call to platform_device_release() tries to kfree the platform data,
> and being it statically allocated memory this triggers a bug from SLAB:
> kernel BUG at mm/slab.c:521!
> In my case this prevented proper device poweroff.
> The question: should these mfd drivers use platform_device_add_data()
> which allocates dynamic memory for *a copy* of platform data? Is this
> simple solution acceptable even if there will be more memory used?
If you move the original data lives in .init there is no duplication.

Best regards

Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | |
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