Messages in this thread Patch in this message | | | Date | Sun, 8 Nov 2009 22:24:34 +0100 | From | Antonio Ospite <> | Subject | Re: Using statically allocated memory for platform_data. |
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On Mon, 2 Nov 2009 11:23:16 +0100 Antonio Ospite <ospite@studenti.unina.it> 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? > Or should we setup platform_data in dynamic memory from the beginning > in board init code? (which would be way less pretty IMHO). >
Just for reference, in our local repository I am _temporarily_ working around the bug with a change like the following, even if I am leaking some memory. Any comments?
diff --git a/drivers/mfd/ezx-pcap.c b/drivers/mfd/ezx-pcap.c index df405af..e4e999b 100644 --- a/drivers/mfd/ezx-pcap.c +++ b/drivers/mfd/ezx-pcap.c @@ -379,12 +379,17 @@ static int pcap_remove_subdev(struct device *dev, void *unused) return 0; }
+static void pcap_subdev_release(struct device *dev) +{ +} + 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.release = pcap_subdev_release; pdev->dev.parent = &pcap->spi->dev; pdev->dev.platform_data = subdev->platform_data;
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