linux-kernel - Re: Clarifying platform_device

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Message-ID: <20080401051947.GD18041@anvil.corenet.prv>
Date:	Tue, 1 Apr 2008 01:19:47 -0400
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Jaya Kumar <jayakumar.lkml@...il.com>
Cc:	Linux Kernel Development <linux-kernel@...r.kernel.org>
Subject: Re: Clarifying platform_device_unregister

Hi Jaya,

On Mon, Mar 31, 2008 at 09:14:35PM -0400, Jaya Kumar wrote:
> Hi,
> 
> I'm trying to figure out a problem I'm experiencing with
> platform_device_unregister. Here's what I'm seeing with a piece of
> test code based on corgi_pm.c:
> 
> static int mydata;
> static struct platform_device *mytest_device;
> static int __devinit mytest_init(void)
> {
>         int ret;
> 
>         mytest_device = platform_device_alloc("no_such_driver", -1);
> 
> // no_such_driver intentionally doesn't exist. i want to test this
> mytest module being insmod-ed/rmmod-ed without ever being bound to a
> platform driver.
> 
>         if (!mytest_device)
>                 return -ENOMEM;
> 
> 
>         mytest_device->dev.platform_data = &mydata;

Platform device code does kfree(pdev->dev.platform_data) unpon
unregistration, so it is not a good idea to assign address of
statically-allocated variable here. You should be using:

	platform_device_add_data(mytest_device, &mydata, sizeof(mydata));


>         ret = platform_device_add(mytest_device);
> 
>         if (ret)
>                 platform_device_put(mytest_device);
> 
>         return ret;
> }
> 
> static void mytest_exit(void)
> {
>         platform_device_unregister(mytest_device);
> }
> 
> 

Hope this helps.

-- 
Dmitry
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