Messages in this thread | | | Date | Mon, 2 Nov 2009 14:51:39 +0000 | From | Ben Dooks <> | Subject | Re: Using statically allocated memory for platform_data. |
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On Mon, Nov 02, 2009 at 11:39:40AM +0100, Uwe Kleine-K?nig wrote: > Hello, > > 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.
they you can't modprobe devices after loading the kernel, so udev autoload and the like become impossible.
-- Ben (ben@fluff.org, http://www.fluff.org/)
'a smiley only costs 4 bytes'
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