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[2.15.156.232]) by smtp.gmail.com with ESMTPSA id t10sm16920730wmi.40.2020.02.24.01.42.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Feb 2020 01:42:04 -0800 (PST) From: Bartosz Golaszewski To: Linus Walleij , Srinivas Kandagatla , Khouloud Touil , Geert Uytterhoeven Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski Subject: [PATCH 2/3] gpiolib: use kref in gpio_desc Date: Mon, 24 Feb 2020 10:41:57 +0100 Message-Id: <20200224094158.28761-3-brgl@bgdev.pl> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200224094158.28761-1-brgl@bgdev.pl> References: <20200224094158.28761-1-brgl@bgdev.pl> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org From: Bartosz Golaszewski GPIO descriptors are freed by consumers using gpiod_put(). The name of this function suggests some reference counting is going on but it's not true. Use kref to actually introduce reference counting for gpio_desc objects. Add a corresponding gpiod_get() helper for increasing the reference count. This doesn't change anything for already existing (correct) drivers but allows us to keep track of GPIO descs used by multiple users. Signed-off-by: Bartosz Golaszewski --- drivers/gpio/gpiolib.c | 40 +++++++++++++++++++++++++++++++---- drivers/gpio/gpiolib.h | 1 + include/linux/gpio/consumer.h | 9 ++++++++ 3 files changed, 46 insertions(+), 4 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index da8ffd40aa97..e97ea1e113a1 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -2798,6 +2798,8 @@ static int gpiod_request_commit(struct gpio_desc *desc, const char *label) goto done; } + kref_init(&desc->ref); + if (chip->request) { /* chip->request may sleep */ spin_unlock_irqrestore(&gpio_lock, flags); @@ -2941,6 +2943,13 @@ void gpiod_free(struct gpio_desc *desc) } } +static void gpiod_free_kref(struct kref *ref) +{ + struct gpio_desc *desc = container_of(ref, struct gpio_desc, ref); + + gpiod_free(desc); +} + /** * gpiochip_is_requested - return string iff signal was requested * @chip: controller managing the signal @@ -5075,18 +5084,41 @@ struct gpio_descs *__must_check gpiod_get_array_optional(struct device *dev, EXPORT_SYMBOL_GPL(gpiod_get_array_optional); /** - * gpiod_put - dispose of a GPIO descriptor - * @desc: GPIO descriptor to dispose of + * gpiod_put - decrease the reference count of a GPIO descriptor + * @desc: GPIO descriptor to unref * * No descriptor can be used after gpiod_put() has been called on it. */ void gpiod_put(struct gpio_desc *desc) { - if (desc) - gpiod_free(desc); + might_sleep(); + + VALIDATE_DESC_VOID(desc); + + kref_put(&desc->ref, gpiod_free_kref); } EXPORT_SYMBOL_GPL(gpiod_put); +/** + * gpiod_ref - increase the reference count of a GPIO descriptor + * @desc: GPIO descriptor to reference + * + * Returns the same gpio_desc after increasing the reference count. + */ +struct gpio_desc *gpiod_ref(struct gpio_desc *desc) +{ + VALIDATE_DESC_PTR(desc); + + if (!test_bit(FLAG_REQUESTED, &desc->flags)) { + pr_warn("gpiolib: unable to increase the reference count of unrequested GPIO descriptor\n"); + return desc; + } + + kref_get(&desc->ref); + return desc; +} +EXPORT_SYMBOL_GPL(gpiod_ref); + /** * gpiod_put_array - dispose of multiple GPIO descriptors * @descs: struct gpio_descs containing an array of descriptors diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h index 3e0aab2945d8..51a92c43dd55 100644 --- a/drivers/gpio/gpiolib.h +++ b/drivers/gpio/gpiolib.h @@ -119,6 +119,7 @@ struct gpio_desc { const char *label; /* Name of the GPIO */ const char *name; + struct kref ref; }; int gpiod_request(struct gpio_desc *desc, const char *label); diff --git a/include/linux/gpio/consumer.h b/include/linux/gpio/consumer.h index bf2d017dd7b7..02b136884923 100644 --- a/include/linux/gpio/consumer.h +++ b/include/linux/gpio/consumer.h @@ -81,6 +81,7 @@ struct gpio_descs *__must_check gpiod_get_array(struct device *dev, struct gpio_descs *__must_check gpiod_get_array_optional(struct device *dev, const char *con_id, enum gpiod_flags flags); +struct gpio_desc *gpiod_ref(struct gpio_desc *desc); void gpiod_put(struct gpio_desc *desc); void gpiod_put_array(struct gpio_descs *descs); @@ -237,6 +238,14 @@ gpiod_get_array_optional(struct device *dev, const char *con_id, return NULL; } +static inline struct gpio_desc *gpiod_ref(struct gpio_desc *desc) +{ + /* GPIO can never have been requested */ + WARN_ON(desc); + + return NULL; +} + static inline void gpiod_put(struct gpio_desc *desc) { might_sleep(); -- 2.25.0