From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bartosz Golaszewski Subject: [PATCH v2 0/4] gpio: fix an incorrect lockdep warning Date: Fri, 16 Sep 2016 18:02:41 +0200 Message-ID: <1474041765-17818-1-git-send-email-bgolaszewski@baylibre.com> Return-path: Received: from mail-wm0-f44.google.com ([74.125.82.44]:38206 "EHLO mail-wm0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932582AbcIPQDC (ORCPT ); Fri, 16 Sep 2016 12:03:02 -0400 Received: by mail-wm0-f44.google.com with SMTP id 1so50078174wmz.1 for ; Fri, 16 Sep 2016 09:03:02 -0700 (PDT) Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Linus Walleij , Alexandre Courbot , Andy Shevchenko , Vignesh R , Yong Li , Geert Uytterhoeven , Peter Zijlstra , Ingo Molnar , Wolfram Sang , Peter Rosin Cc: linux-i2c , linux-gpio , LKML , Bartosz Golaszewski If an I2C GPIO multiplexer is driven by a GPIO provided by an expander when there's a second expander using the same device driver on one of the I2C bus segments, lockdep prints a deadlock warning when trying to set the direction or the value of the GPIOs provided by the second expander. This series exports an already existing function from i2c-core as public API and reuses it in pca953x to pass a correct lock subclass to lockdep. Note: if this series gets merged, I'll prepare follow-up patches for other expanders for which a similar problem could potentially occur. Tested with the following setup: ------- --------- Bus segment 1 | | | | | |--------------- Devices | | SCL/SDA | | | | | Linux |-----------| I2C MUX | - - - - - | | | | | Bus segment 2 | | | | |------------------- ------- | --------- | | | - - - - - ------------ | MUX GPIO | | | | | Devices | GPIO | | | | | Expander 1 |---- - - - - - | | | ------------ | SCL/SDA | ------------ | | | GPIO | | Expander 2 | | | ------------ where expander 1 is a pca9534 and expander 2 is a pca9535. v1 -> v2: - added patches 1/4, 2/4 & 3/4 - used i2c_adapter_depth() in patch 4/4 in order to detect multiple adapter nesting Bartosz Golaszewski (4): i2c: export i2c_adapter_depth() lockdep: make MAX_LOCKDEP_SUBCLASSES unconditionally visible i2c: add a warning to i2c_adapter_depth() gpio: pca953x: fix an incorrect lockdep warning drivers/gpio/gpio-pca953x.c | 2 ++ drivers/i2c/i2c-core.c | 12 +++++------- include/linux/i2c.h | 1 + include/linux/lockdep.h | 4 ++-- 4 files changed, 10 insertions(+), 9 deletions(-) -- 2.7.4