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Subject[PATCH v8 20/22] counter: Implement events_queue_size sysfs attribute
Date
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 <o.rempel@pengutronix.de>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
Documentation/ABI/testing/sysfs-bus-counter | 8 +++++++
drivers/counter/counter-chrdev.c | 23 +++++++++++++++++++
drivers/counter/counter-chrdev.h | 2 ++
drivers/counter/counter-sysfs.c | 25 +++++++++++++++++++++
4 files changed, 58 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-counter b/Documentation/ABI/testing/sysfs-bus-counter
index 847e96f19d19..f6cb2a8b08a7 100644
--- a/Documentation/ABI/testing/sysfs-bus-counter
+++ b/Documentation/ABI/testing/sysfs-bus-counter
@@ -212,6 +212,14 @@ Description:
both edges:
Any state transition.

+What: /sys/bus/counter/devices/counterX/events_queue_size
+KernelVersion: 5.13
+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 16f02df7f73d..53eea894e13f 100644
--- a/drivers/counter/counter-chrdev.c
+++ b/drivers/counter/counter-chrdev.c
@@ -375,6 +375,29 @@ void counter_chrdev_remove(struct counter_device *const counter)
cdev_del(&counter->chrdev);
}

+int counter_chrdev_realloc_queue(struct counter_device *const counter,
+ size_t queue_size)
+{
+ int err;
+ DECLARE_KFIFO_PTR(events, struct counter_event);
+ unsigned long flags;
+
+ /* Allocate new events queue */
+ err = kfifo_alloc(&events, queue_size, GFP_ATOMIC);
+ if (err)
+ return err;
+
+ raw_spin_lock_irqsave(&counter->events_list_lock, flags);
+
+ /* Swap in new events queue */
+ kfifo_free(&counter->events);
+ counter->events.kfifo = events.kfifo;
+
+ raw_spin_unlock_irqrestore(&counter->events_list_lock, flags);
+
+ return 0;
+}
+
static int counter_get_data(struct counter_device *const counter,
const struct counter_comp_node *const comp_node,
u64 *const value)
diff --git a/drivers/counter/counter-chrdev.h b/drivers/counter/counter-chrdev.h
index cf5a318fe540..ff7fb0191852 100644
--- a/drivers/counter/counter-chrdev.h
+++ b/drivers/counter/counter-chrdev.h
@@ -12,5 +12,7 @@
int counter_chrdev_add(struct counter_device *const counter,
const dev_t counter_devt);
void counter_chrdev_remove(struct counter_device *const counter);
+int counter_chrdev_realloc_queue(struct counter_device *const counter,
+ size_t queue_size);

#endif /* _COUNTER_CHRDEV_H_ */
diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c
index 0cb3dba950bc..9abc821a3871 100644
--- a/drivers/counter/counter-sysfs.c
+++ b/drivers/counter/counter-sysfs.c
@@ -13,6 +13,7 @@
#include <linux/sysfs.h>
#include <linux/types.h>

+#include "counter-chrdev.h"
#include "counter-sysfs.h"

/**
@@ -737,12 +738,30 @@ 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 = counter->events.kfifo.mask + 1;
+ return 0;
+}
+
+static int counter_events_queue_size_write(struct counter_device *counter,
+ u64 val)
+{
+ return counter_chrdev_realloc_queue(counter, val);
+}
+
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 *group)
{
@@ -781,6 +800,12 @@ static int counter_sysfs_attr_add(struct counter_device *const counter,
if (err < 0)
return err;

+ /* Create num_counts attribute */
+ err = counter_attr_create(dev, 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;
--
2.30.0
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