From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bamvor Jian Zhang Subject: [PATCH] gpiolib: rewrite gpiochip_add_to_list Date: Fri, 8 Jan 2016 14:37:14 +0800 Message-ID: <1452235035-828-1-git-send-email-bamvor.zhangjian@linaro.org> Return-path: Received: from mail-pf0-f182.google.com ([209.85.192.182]:33812 "EHLO mail-pf0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750721AbcAHGhx (ORCPT ); Fri, 8 Jan 2016 01:37:53 -0500 Received: by mail-pf0-f182.google.com with SMTP id q63so5471603pfb.1 for ; Thu, 07 Jan 2016 22:37:52 -0800 (PST) Sender: linux-gpio-owner@vger.kernel.org List-Id: linux-gpio@vger.kernel.org To: linux-gpio@vger.kernel.org Cc: linus.walleij@linaro.org, broonie@kernel.org, julien.grossholtz@savoirfairelinux.com, arnd@arndb.de, Bamvor Jian Zhang The original code of gpiochip_add_to_list is not very clear which lead to bugs or compiling warning, reference the following patches: Bugs: 1. Commit ef7c7553039b ("gpiolib: improve overlap check of range of gpio"). 2. "[PATCH] gpiolib: fix chip order in gpio list" [1] Warning: 1. Commit e28ecca6eac4 ("gpio: fix warning about iterator"). of gpio"). There is a off-list discussion about how to improve it consequently. This commit try to follow this by rewriting the whole functions. Tested pass with my gpio mockup driver and test scripts[2]. [1] http://www.spinics.net/lists/kernel/msg2156917.html [2] http://www.spinics.net/lists/linux-gpio/msg09598.html Suggested-by: Arnd Bergmann Signed-off-by: Bamvor Jian Zhang --- drivers/gpio/gpiolib.c | 65 ++++++++++++++++++++++---------------------------- 1 file changed, 28 insertions(+), 37 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index 3db34e7..b9cc01f 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -189,55 +189,46 @@ EXPORT_SYMBOL_GPL(gpiod_get_direction); */ static int gpiochip_add_to_list(struct gpio_chip *chip) { - struct gpio_chip *iterator; - struct gpio_chip *previous = NULL; + struct gpio_chip *prev, *next; if (list_empty(&gpio_chips)) { - list_add_tail(&chip->list, &gpio_chips); + /* initial entry in list */ + list_add(&chip->list, &gpio_chips); return 0; } - list_for_each_entry(iterator, &gpio_chips, list) { - if (iterator->base >= chip->base + chip->ngpio) { - /* - * Iterator is the first GPIO chip so there is no - * previous one - */ - if (!previous) { - goto found; - } else { - /* - * We found a valid range(means - * [base, base + ngpio - 1]) between previous - * and iterator chip. - */ - if (previous->base + previous->ngpio - <= chip->base) - goto found; - } - } - previous = iterator; + next = list_entry(gpio_chips.next, struct gpio_chip, list); + if (chip->base + chip->ngpio <= next->base) { + /* add before first entry */ + list_add(&chip->list, &gpio_chips); + return 0; } - /* - * We are beyond the last chip in the list and iterator now - * points to the head. - * Let iterator point to the last chip in the list. - */ + prev = list_entry(gpio_chips.prev, struct gpio_chip, list); + if (prev->base + prev->ngpio <= chip->base) { + /* add behind last entry */ + list_add_tail(&chip->list, &gpio_chips); + return 0; + } - iterator = list_last_entry(&gpio_chips, struct gpio_chip, list); - if (iterator->base + iterator->ngpio <= chip->base) - goto found; + list_for_each_entry_safe(prev, next, &gpio_chips, list) + if (chip->base > prev->base) + break; - dev_err(chip->parent, - "GPIO integer space overlap, cannot add chip\n"); - return -EBUSY; + if (&prev->list != &gpio_chips && + &next->list != &gpio_chips && + prev->base + prev->ngpio <= chip->base && + chip->base + chip->ngpio <= next->base) { + /* add between prev and next */ + list_add(&chip->list, &prev->list); + return 0; + } -found: - list_add_tail(&chip->list, &iterator->list); - return 0; + dev_err(chip->parent, "GPIO integer space overlap, cannot add chip\n"); + return -EBUSY; } + /** * Convert a GPIO name to its descriptor */ -- 2.1.4