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Tue, 13 Jul 2021 02:55:01 -0700 (PDT) From: William Breathitt Gray To: jic23@kernel.org Cc: linux-stm32@st-md-mailman.stormreply.com, kernel@pengutronix.de, a.fatoum@pengutronix.de, kamel.bouhara@bootlin.com, gwendal@chromium.org, alexandre.belloni@bootlin.com, david@lechnology.com, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, syednwaris@gmail.com, patrick.havelange@essensium.com, fabrice.gasnier@st.com, mcoquelin.stm32@gmail.com, alexandre.torgue@st.com, o.rempel@pengutronix.de, jarkko.nikula@linux.intel.com, William Breathitt Gray Subject: [PATCH v13 15/17] counter: Implement events_queue_size sysfs attribute Date: Tue, 13 Jul 2021 18:53:19 +0900 Message-Id: <7ec39add7db353b4e8d1c53f52b356007364ad14.1626165765.git.vilhelm.gray@gmail.com> X-Mailer: git-send-email 2.32.0 In-Reply-To: References: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210713_025502_835469_FF765F1E X-CRM114-Status: GOOD ( 21.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org The events_queue_size sysfs attribute provides a way for users to dynamically configure the Counter events queue size for the Counter character device interface. The size is in number of struct counter_event data structures. The number of elements will be rounded-up to a power of 2 due to a requirement of the kfifo_alloc function called during reallocation of the queue. Cc: Oleksij Rempel Signed-off-by: William Breathitt Gray --- Documentation/ABI/testing/sysfs-bus-counter | 8 ++++ drivers/counter/counter-chrdev.c | 6 +++ drivers/counter/counter-sysfs.c | 45 +++++++++++++++++++++ include/linux/counter.h | 2 + 4 files changed, 61 insertions(+) diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter index e0e99adb0ecc..84ebb1ed28ed 100644 --- a/Documentation/ABI/testing/sysfs-bus-counter +++ b/Documentation/ABI/testing/sysfs-bus-counter @@ -233,6 +233,14 @@ Description: shorter or equal to configured value are ignored. Value 0 means filter is disabled. +What: /sys/bus/counter/devices/counterX/events_queue_size +KernelVersion: 5.15 +Contact: linux-iio@vger.kernel.org +Description: + Size of the Counter events queue in number of struct + counter_event data structures. The number of elements will be + rounded-up to a power of 2. + What: /sys/bus/counter/devices/counterX/name KernelVersion: 5.2 Contact: linux-iio@vger.kernel.org diff --git a/drivers/counter/counter-chrdev.c b/drivers/counter/counter-chrdev.c index d5af82d3c04b..cf94e8f1c4ea 100644 --- a/drivers/counter/counter-chrdev.c +++ b/drivers/counter/counter-chrdev.c @@ -3,6 +3,7 @@ * Generic Counter character device interface * Copyright (C) 2020 William Breathitt Gray */ +#include #include #include #include @@ -336,6 +337,9 @@ static int counter_chrdev_open(struct inode *inode, struct file *filp) typeof(*counter), chrdev); + if (test_and_set_bit_lock(0, counter->chrdev_lock)) + return -EBUSY; + get_device(&counter->dev); filp->private_data = counter; @@ -352,6 +356,7 @@ static int counter_chrdev_release(struct inode *inode, struct file *filp) return err; put_device(&counter->dev); + clear_bit_unlock(0, counter->chrdev_lock); return 0; } @@ -376,6 +381,7 @@ int counter_chrdev_add(struct counter_device *const counter) mutex_init(&counter->events_lock); /* Initialize character device */ + clear_bit(0, counter->chrdev_lock); cdev_init(&counter->chrdev, &counter_fops); /* Allocate Counter events queue */ diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c index df1d75e0d7b8..d2d6495f73c5 100644 --- a/drivers/counter/counter-sysfs.c +++ b/drivers/counter/counter-sysfs.c @@ -3,11 +3,13 @@ * Generic Counter sysfs interface * Copyright (C) 2020 William Breathitt Gray */ +#include #include #include #include #include #include +#include #include #include #include @@ -785,12 +787,49 @@ static int counter_num_counts_read(struct counter_device *counter, u8 *val) return 0; } +static int counter_events_queue_size_read(struct counter_device *counter, + u64 *val) +{ + *val = kfifo_size(&counter->events); + return 0; +} + +static int counter_events_queue_size_write(struct counter_device *counter, + u64 val) +{ + DECLARE_KFIFO_PTR(events, struct counter_event); + int err = 0; + + /* Verify chrdev is not currently being used */ + if (test_and_set_bit_lock(0, counter->chrdev_lock)) + return -EBUSY; + + /* Allocate new events queue */ + err = kfifo_alloc(&events, val, GFP_KERNEL); + if (err) + goto exit_early; + + /* Swap in new events queue */ + kfifo_free(&counter->events); + counter->events.kfifo = events.kfifo; + +exit_early: + clear_bit_unlock(0, counter->chrdev_lock); + + return err; +} + static struct counter_comp counter_num_signals_comp = COUNTER_COMP_DEVICE_U8("num_signals", counter_num_signals_read, NULL); static struct counter_comp counter_num_counts_comp = COUNTER_COMP_DEVICE_U8("num_counts", counter_num_counts_read, NULL); +static struct counter_comp counter_events_queue_size_comp = + COUNTER_COMP_DEVICE_U64("events_queue_size", + counter_events_queue_size_read, + counter_events_queue_size_write); + static int counter_sysfs_attr_add(struct counter_device *const counter, struct counter_attribute_group *cattr_group) { @@ -829,6 +868,12 @@ static int counter_sysfs_attr_add(struct counter_device *const counter, if (err < 0) return err; + /* Create events_queue_size attribute */ + err = counter_attr_create(dev, cattr_group, + &counter_events_queue_size_comp, scope, NULL); + if (err < 0) + return err; + /* Create an attribute for each extension */ for (i = 0; i < counter->num_ext; i++) { ext = &counter->ext[i]; diff --git a/include/linux/counter.h b/include/linux/counter.h index 895d60a238a9..bfd96fa1f7fe 100644 --- a/include/linux/counter.h +++ b/include/linux/counter.h @@ -297,6 +297,7 @@ struct counter_ops { * @events: queue of detected Counter events * @events_wait: wait queue to allow blocking reads of Counter events * @events_lock: lock to protect Counter events queue read operations + * @chrdev_lock: lock to limit chrdev to a single open at a time */ struct counter_device { const char *name; @@ -323,6 +324,7 @@ struct counter_device { DECLARE_KFIFO_PTR(events, struct counter_event); wait_queue_head_t events_wait; struct mutex events_lock; + DECLARE_BITMAP(chrdev_lock, 1); }; int counter_register(struct counter_device *const counter);