Re: [PATCH v2 0/4] gpio: fix an incorrect lockdep warning

From: Bartosz Golaszewski
Date: Sun Sep 18 2016 - 15:45:15 EST

2016-09-18 21:43 GMT+02:00 Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>:
> 2016-09-18 10:52 GMT+02:00 Peter Rosin <peda@xxxxxxxxxx>:
>> On 2016-09-16 19:58, Wolfram Sang wrote:
>>> Same here. And if it prevents us from false positive lockdep reports, I
>>> am all for fixing it.
>> Except it doesn't, when I think some more about it...
>> If you have two gpio-expanders on the same depth but on different i2c
>> branches you still end up with a splat if one is used to control a mux
>> to reach the other.
>> The only way to solve it for good, that I see, is to have every instance
>> of the gpio-expander mutex in its own class. That might lead to many
>> lockdep classes but then again, how many gpio expanders could there be
>> in a system? A dozen or two seems extreme, so maybe that is the correct
>> approach anyway?
> Wouldn't it be enough to have a separate class for every base (as in:
> not having any parent adapters) i2c adapter?


Of course not - since we could have two branches deeper on the tree
with the same problem.

Nevermind my last e-mail.

Best regards,
Bartosz Golaszewski