From patchwork Mon Mar 10 12:54:50 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mika Westerberg X-Patchwork-Id: 3803001 Return-Path: X-Original-To: patchwork-linux-acpi@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id F03299F369 for ; Mon, 10 Mar 2014 12:56:52 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 0813920265 for ; Mon, 10 Mar 2014 12:56:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F3CF720257 for ; Mon, 10 Mar 2014 12:56:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753394AbaCJM4d (ORCPT ); Mon, 10 Mar 2014 08:56:33 -0400 Received: from mga11.intel.com ([192.55.52.93]:61169 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753530AbaCJMzA (ORCPT ); Mon, 10 Mar 2014 08:55:00 -0400 Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga102.fm.intel.com with ESMTP; 10 Mar 2014 05:54:58 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.97,623,1389772800"; d="scan'208";a="495438833" Received: from blue.fi.intel.com ([10.237.72.156]) by fmsmga002.fm.intel.com with ESMTP; 10 Mar 2014 05:54:55 -0700 Received: by blue.fi.intel.com (Postfix, from userid 1004) id 04CC5E0097; Mon, 10 Mar 2014 14:54:54 +0200 (EET) From: Mika Westerberg To: Linus Walleij , "Rafael J. Wysocki" Cc: Alexandre Courbot , Lan Tianyu , Lv Zheng , Alan Cox , Mathias Nyman , linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, Mika Westerberg Subject: [PATCH v2 1/5] gpiolib: Allow GPIO chips to request their own GPIOs Date: Mon, 10 Mar 2014 14:54:50 +0200 Message-Id: <1394456094-21671-2-git-send-email-mika.westerberg@linux.intel.com> X-Mailer: git-send-email 1.9.0 In-Reply-To: <1394456094-21671-1-git-send-email-mika.westerberg@linux.intel.com> References: <1394456094-21671-1-git-send-email-mika.westerberg@linux.intel.com> Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Sometimes it is useful to allow GPIO chips themselves to request GPIOs they own through gpiolib API. One use case is ACPI ASL code that should be able to toggle GPIOs through GPIO operation regions. We can't use gpio_request() because it will pin the module to the kernel forever (it calls try_module_get()). To solve this we move module refcount manipulation to gpiod_request() and let __gpiod_request() handle the actual request. This changes the sequence a bit as now try_module_get() is called outside of gpio_lock (I think this is safe, try_module_get() handles serialization it needs already). Then we provide gpiolib internal functions gpiochip_request/free_own_desc() that do the same as gpio_request() but don't manipulate module refrence count. This allows the GPIO chip driver to request and free descriptors it owns without being pinned to the kernel forever. Signed-off-by: Mika Westerberg Reviewed-by: Alexandre Courbot --- drivers/gpio/gpiolib.c | 100 ++++++++++++++++++++++++++++++++++++------------- drivers/gpio/gpiolib.h | 3 ++ 2 files changed, 76 insertions(+), 27 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index f60d74bc2fce..61de1efe85fd 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -1458,26 +1458,14 @@ EXPORT_SYMBOL_GPL(gpiochip_remove_pin_ranges); * on each other, and help provide better diagnostics in debugfs. * They're called even less than the "set direction" calls. */ -static int gpiod_request(struct gpio_desc *desc, const char *label) +static int __gpiod_request(struct gpio_desc *desc, const char *label) { - struct gpio_chip *chip; - int status = -EPROBE_DEFER; + struct gpio_chip *chip = desc->chip; + int status; unsigned long flags; - if (!desc) { - pr_warn("%s: invalid GPIO\n", __func__); - return -EINVAL; - } - spin_lock_irqsave(&gpio_lock, flags); - chip = desc->chip; - if (chip == NULL) - goto done; - - if (!try_module_get(chip->owner)) - goto done; - /* NOTE: gpio_request() can be called in early boot, * before IRQs are enabled, for non-sleeping (SOC) GPIOs. */ @@ -1487,7 +1475,6 @@ static int gpiod_request(struct gpio_desc *desc, const char *label) status = 0; } else { status = -EBUSY; - module_put(chip->owner); goto done; } @@ -1499,7 +1486,6 @@ static int gpiod_request(struct gpio_desc *desc, const char *label) if (status < 0) { desc_set_label(desc, NULL); - module_put(chip->owner); clear_bit(FLAG_REQUESTED, &desc->flags); goto done; } @@ -1511,9 +1497,34 @@ static int gpiod_request(struct gpio_desc *desc, const char *label) spin_lock_irqsave(&gpio_lock, flags); } done: + spin_unlock_irqrestore(&gpio_lock, flags); + return status; +} + +static int gpiod_request(struct gpio_desc *desc, const char *label) +{ + int status = -EPROBE_DEFER; + struct gpio_chip *chip; + + if (!desc) { + pr_warn("%s: invalid GPIO\n", __func__); + return -EINVAL; + } + + chip = desc->chip; + if (!chip) + goto done; + + if (try_module_get(chip->owner)) { + status = __gpiod_request(desc, label); + if (status < 0) + module_put(chip->owner); + } + +done: if (status) gpiod_dbg(desc, "%s: status %d\n", __func__, status); - spin_unlock_irqrestore(&gpio_lock, flags); + return status; } @@ -1523,18 +1534,14 @@ int gpio_request(unsigned gpio, const char *label) } EXPORT_SYMBOL_GPL(gpio_request); -static void gpiod_free(struct gpio_desc *desc) +static bool __gpiod_free(struct gpio_desc *desc) { + bool ret = false; unsigned long flags; struct gpio_chip *chip; might_sleep(); - if (!desc) { - WARN_ON(extra_checks); - return; - } - gpiod_unexport(desc); spin_lock_irqsave(&gpio_lock, flags); @@ -1548,15 +1555,23 @@ static void gpiod_free(struct gpio_desc *desc) spin_lock_irqsave(&gpio_lock, flags); } desc_set_label(desc, NULL); - module_put(desc->chip->owner); clear_bit(FLAG_ACTIVE_LOW, &desc->flags); clear_bit(FLAG_REQUESTED, &desc->flags); clear_bit(FLAG_OPEN_DRAIN, &desc->flags); clear_bit(FLAG_OPEN_SOURCE, &desc->flags); - } else - WARN_ON(extra_checks); + ret = true; + } spin_unlock_irqrestore(&gpio_lock, flags); + return ret; +} + +static void gpiod_free(struct gpio_desc *desc) +{ + if (desc && __gpiod_free(desc)) + module_put(desc->chip->owner); + else + WARN_ON(extra_checks); } void gpio_free(unsigned gpio) @@ -1678,6 +1693,37 @@ const char *gpiochip_is_requested(struct gpio_chip *chip, unsigned offset) } EXPORT_SYMBOL_GPL(gpiochip_is_requested); +/** + * gpiochip_request_own_desc - Allow GPIO chip to request its own descriptor + * @desc: GPIO descriptor to request + * @label: label for the GPIO + * + * Function allows GPIO chip drivers to request and use their own GPIO + * descriptors via gpiolib API. Difference to gpiod_request() is that this + * function will not increase reference count of the GPIO chip module. This + * allows the GPIO chip module to be unloaded as needed (we assume that the + * GPIO chip driver handles freeing the GPIOs it has requested). + */ +int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label) +{ + if (!desc || !desc->chip) + return -EINVAL; + + return __gpiod_request(desc, label); +} + +/** + * gpiochip_free_own_desc - Free GPIO requested by the chip driver + * @desc: GPIO descriptor to free + * + * Function frees the given GPIO requested previously with + * gpiochip_request_own_desc(). + */ +void gpiochip_free_own_desc(struct gpio_desc *desc) +{ + if (desc) + __gpiod_free(desc); +} /* Drivers MUST set GPIO direction before making get/set calls. In * some cases this is done in early boot, before IRQs are enabled. diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h index 82be586c1f90..cf092941a9fd 100644 --- a/drivers/gpio/gpiolib.h +++ b/drivers/gpio/gpiolib.h @@ -43,4 +43,7 @@ acpi_get_gpiod_by_index(struct device *dev, int index, } #endif +int gpiochip_request_own_desc(struct gpio_desc *desc, const char *label); +void gpiochip_free_own_desc(struct gpio_desc *desc); + #endif /* GPIOLIB_H */