Re: [PATCH] of: provide of_platform_unpopulate()

[Rob Herring <robherring2@gmail.com>]

On 07/21/2013 09:42 AM, Rob Herring wrote:
> On 07/19/2013 01:14 PM, Sebastian Andrzej Siewior wrote:
>> So I called of_platform_populate() on a device to get each child device
>> probed and on rmmod and I need to reverse its doing. After a quick grep
>> I did what others did as well and rmmod ended in:
>>
>> | Unable to handle kernel NULL pointer dereference at virtual address 00000018
>> | PC is at release_resource+0x18/0x80
>> | Process rmmod (pid: 2005, stack limit = 0xedc30238)
>> | [<c003add0>] (release_resource+0x18/0x80) from [<c0300e08>] (platform_device_del+0x78/0xac)
>> | [<c0300e08>] (platform_device_del+0x78/0xac) from [<c0301358>] (platform_device_unregister+0xc/0x18)
>>
>> The problem is that platform_device_del() "releases" each ressource in its
>> tree. This does not work on platform_devices created by OF becuase they
>> were never added via insert_resource(). As a consequence old->parent in
>> __release_resource() is NULL and we explode while accessing ->child.
>> So I either I do something completly wrong _or_ nobody here tested the
>> rmmod path of their driver.
> 
> Wouldn't the correct fix be to call insert_resource somehow? The problem
> I have is that while of_platform_populate is all about parsing the DT
> and creating devices, the removal side has nothing to do with DT. So
> this should not be in the DT code. I think the core device code should
> be able to handle removal if the device creation side is done correctly.
> 
> It looks to me like of_device_add either needs to call
> platform_device_add rather than device_add. I think the device name
> setting in platform_device_add should be a nop. If not, a check that the
> name is already set could be added.
> 

BTW, it looks like Grant has attempted this already:

commit 02bbde7849e68e193cefaa1885fe0df0f03c9fcd
Author: Grant Likely <grant.likely@secretlab.ca>
Date:   Sun Feb 17 20:03:27 2013 +0000

    Revert "of: use platform_device_add"

    This reverts commit aac73f34542bc7ae4317928d2eabfeb21d247323. That
    commit causes two kinds of breakage; it breaks registration of AMBA
    devices when one of the parent nodes already contains overlapping
    resource regions, and it breaks calls to request_region() by device
    drivers in certain conditions where there are overlapping memory
    regions. Both of these problems can probably be fixed, but it is better
    to back out the commit and get a proper fix designed before trying
again.

    Signed-off-by: Grant Likely <grant.likely@secretlab.ca>


Rob