[Letux-kernel] omap-gpmc gta04 regression 4.7-rc1

Grygorii Strashko grygorii.strashko at ti.com
Tue Jun 7 17:29:16 CEST 2016


On 06/07/2016 04:33 PM, Linus Walleij wrote:
> On Tue, Jun 7, 2016 at 9:50 AM, Roger Quadros <rogerq at ti.com> wrote:
> 
>> Linus, any idea why of_gpiochip_find_and_xlate() would do a NULL pointer dereference?
> 
> Nope. I see this uses the array fetch function which I did patch around but
> "should" not affect this.
> 
>> We have a case here where the GPMC driver registers a gpiochip but after a while
>> unregisters it due to some other orthogonal resource not being available.
>> Is this registering and unregistering considered acceptable from gpiochip point of view?
> 
> That would be if it doesn't really go away aftert gpiochip_remove() because
> some refcount doesn't go zero, so double-check that. It should be fine
> anyway though ... just the instance floating around somewhere.
> 

Linus, I've tried to find place in gpiolib.c where gpiochip is removed
from gpio_devices list as part of gpiochip_remove(), but I can't. Am I missed smth.?

If that is the case then such kind of crash is possible, because gpiochip_find()
uses this list.

-- 
regards,
-grygorii


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