On 07/21/2013 09:42 AM, Rob Herring wrote:

On 07/19/2013 01:14 PM, Sebastian Andrzej Siewior wrote:

quoted

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 [off-list ref]
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 [off-list ref]


Rob