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@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> Rob -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html