[PATCH v5 3/5] counter: Add character device interface

William Breathitt Gray
2020-09-27T02:20:21Z

This patch introduces a character device interface for the Counter
subsystem. Device data is exposed through standard character device read
operations. Device data is gathered when a Counter event is pushed by
the respective Counter device driver. Configuration is handled via ioctl
operations on the respective Counter character device node.

A high-level view of how a count value is passed down from a counter
driver is exemplified by the following. The driver callbacks are first
registered to the Counter core component for use by the Counter
userspace interface components:

+----------------------------+
| Counter device driver |
+----------------------------+
| Processes data from device |
+----------------------------+
|
-------------------
/ driver callbacks /
-------------------
|
V
+----------------------+
| Counter core |
+----------------------+
| Routes device driver |
| callbacks to the |
| userspace interfaces |
+----------------------+
|
-------------------
/ driver callbacks /
-------------------
|
+---------------+---------------+
| |
V V
+--------------------+ +---------------------+
| Counter sysfs | | Counter chrdev |
+--------------------+ +---------------------+
| Translates to the | | Translates to the |
| standard Counter | | standard Counter |
| sysfs output | | character device |
+--------------------+ +---------------------+

Thereafter, data can be transferred directly between the Counter device
driver and Counter userspace interface:

----------------------
/ Counter device \
+----------------------+
| Count register: 0x28 |
+----------------------+
|
-----------------
/ raw count data /
-----------------
|
V
+----------------------------+
| Counter device driver |
+----------------------------+
| Processes data from device |
|----------------------------|
| Type: u64 |
| Value: 42 |
+----------------------------+
|
----------
/ u64 /
----------
|
+---------------+---------------+
| |
V V
+--------------------+ +---------------------+
| Counter sysfs | | Counter chrdev |
+--------------------+ +---------------------+
| Translates to the | | Translates to the |
| standard Counter | | standard Counter |
| sysfs output | | character device |
|--------------------| |---------------------|
| Type: const char * | | Type: u64 |
| Value: "42" | | Value: 42 |
+--------------------+ +---------------------+
| |
--------------- -----------------------
/ const char * / / struct counter_event /
--------------- -----------------------
| |
| V
| +-----------+
| | read |
| +-----------+
| \ Count: 42 /
| -----------
|
V
+--------------------------------------------------+
| `/sys/bus/counter/devices/counterX/countY/count` |
+--------------------------------------------------+
\ Count: "42" /
--------------------------------------------------

Counter character device nodes are created under the `/dev` directory as
`counterX`, where `X` is the respective counter device id. Defines for
the standard Counter data types are exposed via the userspace
`include/uapi/linux/counter.h` file.

Counter events
--------------
Counter device drivers can support Counter events by utilizing the
`counter_push_event` function:

int counter_push_event(struct counter_device *const counter,
const u8 event, const u8 channel);

The event id is specified by the `event` parameter; the event channel id
is specified by the `channel` parameter. When this function is called,
the Counter data associated with the respective event is gathered, and a
`struct counter_event` is generated for each datum and pushed to
userspace.

Counter events can be configured by users to report various Counter
data of interest. This can be conceptualized as a list of Counter
component read calls to perform. For example:

+~~~~~~~~~~~~~~~~~~~~~~~~+~~~~~~~~~~~~~~~~~~~~~~~~+
| COUNTER_EVENT_OVERFLOW | COUNTER_EVENT_INDEX |
+~~~~~~~~~~~~~~~~~~~~~~~~+~~~~~~~~~~~~~~~~~~~~~~~~+
| Channel 0 | Channel 0 |
+------------------------+------------------------+
| * Count 0 | * Signal 0 |
| * Count 1 | * Signal 0 Extension 0 |
| * Signal 3 | * Extension 4 |
| * Count 4 Extension 2 +------------------------+
| * Signal 5 Extension 0 | Channel 1 |
| +------------------------+
| | * Signal 4 |
| | * Signal 4 Extension 0 |
| | * Count 7 |
+------------------------+------------------------+

When `counter_push_event(counter, COUNTER_EVENT_INDEX, 1)` is called for
example, it will go down the list for the `COUNTER_EVENT_INDEX` event
channel 1 and execute the read callbacks for Signal 4, Signal 4
Extension 0, and Count 4 -- the data returned for each is pushed to a
kfifo as a `struct counter_event`, which userspace can retrieve via a
standard read operation on the respective character device node.

Userspace
---------
Userspace applications can configure Counter events via ioctl operations
on the Counter character device node. There following ioctl codes are
supported and provided by the `linux/counter.h` userspace header file:

* COUNTER_CLEAR_WATCHES_IOCTL:
Clear all Counter watches from all events

* COUNTER_SET_WATCH_IOCTL:
Set a Counter watch for the specified event

* COUNTER_LOAD_WATCHES_IOCTL:
Activates the Counter watches set earlier

To configure events to gather Counter data, users first populate a
`struct counter_watch` with the relevant event id, event channel id, and
the information for the desired Counter component from which to read,
and then pass it via the `COUNTER_SET_WATCH_IOCTL` ioctl command.

The `COUNTER_SET_WATCH_IOCTL` command will buffer these Counter watches.
When ready, the `COUNTER_LOAD_WATCHES_IOCTL` ioctl command may be used
to activate these Counter watches.

Userspace applications can then execute a `read` operation (optionally
calling `poll` first) on the Counter character device node to retrieve
`struct counter_event` elements with the desired data.

For example, the following userspace code opens `/dev/counter0`,
configures the `COUNTER_EVENT_INDEX` event channel 0 to gather Count 0
and Count 1, and prints out the data as it becomes available on the
character device node:

#include <fcntl.h>
#include <linux/counter.h>
#include <poll.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <unistd.h>

struct counter_watch watches[2] = {
{
.event = COUNTER_EVENT_INDEX,
.channel = 0,
.component.scope = COUNTER_SCOPE_COUNT,
.component.parent = 0,
.component.type = COUNTER_COMPONENT_COUNT,
},
{
.event = COUNTER_EVENT_INDEX,
.channel = 0,
.component.scope = COUNTER_SCOPE_COUNT,
.component.parent = 1,
.component.type = COUNTER_COMPONENT_COUNT,
},
};

int main(void)
{
struct pollfd pfd = { .events = POLLIN };
struct counter_event event_data[2];

pfd.fd = open("/dev/counter0", O_RDWR);

ioctl(pfd.fd, COUNTER_SET_WATCH_IOCTL, watches);
ioctl(pfd.fd, COUNTER_SET_WATCH_IOCTL, watches + 1);
ioctl(pfd.fd, COUNTER_LOAD_WATCHES_IOCTL);

for (;;) {
poll(&pfd, 1, -1);

read(pfd.fd, event_data, sizeof(event_data));

printf("Timestamp 0: %llu\nCount 0: %llu\n"
"Timestamp 1: %llu\nCount 1: %llu\n",
(unsigned long long)event_data[0].timestamp,
(unsigned long long)event_data[0].value_u64,
(unsigned long long)event_data[1].timestamp,
(unsigned long long)event_data[1].value_u64);
}

return 0;
}

Cc: David Lechner <david@lechnology.com>
Cc: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
MAINTAINERS | 1 +
drivers/counter/Makefile | 2 +-
drivers/counter/counter-chrdev.c | 451 +++++++++++++++++++++++++++++++
drivers/counter/counter-chrdev.h | 16 ++
drivers/counter/counter-core.c | 38 ++-
drivers/counter/counter-sysfs.c | 109 +++++++-
include/linux/counter.h | 48 ++--
include/uapi/linux/counter.h | 99 +++++++
8 files changed, 720 insertions(+), 44 deletions(-)
create mode 100644 drivers/counter/counter-chrdev.c
create mode 100644 drivers/counter/counter-chrdev.h
create mode 100644 include/uapi/linux/counter.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 4969e997061a..de6685a683c8 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4459,6 +4459,7 @@ F: Documentation/ABI/testing/sysfs-bus-counter*
F: Documentation/driver-api/generic-counter.rst
F: drivers/counter/
F: include/linux/counter.h
+F: include/uapi/linux/counter.h

CPMAC ETHERNET DRIVER
M: Florian Fainelli <f.fainelli@gmail.com>
diff --git a/drivers/counter/Makefile b/drivers/counter/Makefile
index cbe1d06af6a9..c4870eb5b1dd 100644
--- a/drivers/counter/Makefile
+++ b/drivers/counter/Makefile
@@ -4,7 +4,7 @@
#

obj-$(CONFIG_COUNTER) += counter.o
-counter-y := counter-core.o counter-sysfs.o
+counter-y := counter-core.o counter-sysfs.o counter-chrdev.o

obj-$(CONFIG_104_QUAD_8) += 104-quad-8.o
obj-$(CONFIG_STM32_TIMER_CNT) += stm32-timer-cnt.o
diff --git a/drivers/counter/counter-chrdev.c b/drivers/counter/counter-chrdev.c
new file mode 100644
index 000000000000..2be3846e4105
--- /dev/null
+++ b/drivers/counter/counter-chrdev.c
@@ -0,0 +1,451 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Generic Counter character device interface
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+
+#include <linux/cdev.h>
+#include <linux/counter.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/errno.h>
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/list.h>
+#include <linux/poll.h>
+#include <linux/kdev_t.h>
+#include <linux/kfifo.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/timekeeping.h>
+#include <linux/types.h>
+#include <linux/wait.h>
+#include <linux/uaccess.h>
+
+#include "counter-chrdev.h"
+
+struct counter_comp_node {
+ struct list_head l;
+ struct counter_component component;
+ struct counter_comp comp;
+ void *parent;
+};
+
+struct counter_event_node {
+ struct list_head l;
+ u8 event;
+ u8 channel;
+ struct list_head comp_list;
+};
+
+static ssize_t counter_chrdev_read(struct file *filp, char __user *buf,
+ size_t len, loff_t *f_ps)
+{
+ struct counter_device *const counter = filp->private_data;
+ int err;
+ unsigned long flags;
+ unsigned int copied;
+
+ if (len < sizeof(struct counter_event))
+ return -EINVAL;
+
+ do {
+ if (kfifo_is_empty(&counter->events)) {
+ if (filp->f_flags & O_NONBLOCK)
+ return -EAGAIN;
+
+ err = wait_event_interruptible(counter->events_wait,
+ !kfifo_is_empty(&counter->events));
+ if (err)
+ return err;
+ }
+
+ raw_spin_lock_irqsave(&counter->events_lock, flags);
+ err = kfifo_to_user(&counter->events, buf, len, &copied);
+ raw_spin_unlock_irqrestore(&counter->events_lock, flags);
+ if (err)
+ return err;
+ } while (!copied);
+
+ return copied;
+}
+
+static __poll_t counter_chrdev_poll(struct file *filp,
+ struct poll_table_struct *pollt)
+{
+ struct counter_device *const counter = filp->private_data;
+ __poll_t events = 0;
+
+ poll_wait(filp, &counter->events_wait, pollt);
+
+ if (!kfifo_is_empty(&counter->events))
+ events = EPOLLIN | EPOLLRDNORM;
+
+ return events;
+}
+
+static void counter_events_list_free(struct list_head *const events_list)
+{
+ struct counter_event_node *p, *n;
+ struct counter_comp_node *q, *o;
+
+ list_for_each_entry_safe(p, n, events_list, l) {
+ /* Free associated component nodes */
+ list_for_each_entry_safe(q, o, &p->comp_list, l) {
+ list_del(&q->l);
+ kfree(q);
+ }
+
+ /* Free event node */
+ list_del(&p->l);
+ kfree(p);
+ }
+}
+
+static int counter_set_event_node(struct counter_device *const counter,
+ struct counter_watch *const watch,
+ const struct counter_comp_node *const cfg)
+{
+ struct counter_event_node *event_node;
+ int err;
+ struct counter_comp_node *comp_node;
+
+ /* Search for event in the list */
+ list_for_each_entry(event_node, &counter->next_events_list, l)
+ if (event_node->event == watch->event &&
+ event_node->channel == watch->channel)
+ break;
+
+ /* If event is not already in the list */
+ if (&event_node->l == &counter->next_events_list) {
+ /* Allocate new event node */
+ event_node = kmalloc(sizeof(*event_node), GFP_ATOMIC);
+ if (!event_node)
+ return -ENOMEM;
+
+ /* Configure event node and add to the list */
+ event_node->event = watch->event;
+ event_node->channel = watch->channel;
+ INIT_LIST_HEAD(&event_node->comp_list);
+ list_add(&event_node->l, &counter->next_events_list);
+ }
+
+ /* Check if component watch has already been set before */
+ list_for_each_entry(comp_node, &event_node->comp_list, l)
+ if (comp_node->parent == cfg->parent &&
+ comp_node->comp.count_u8_read == cfg->comp.count_u8_read)
+ return -EINVAL;
+
+ /* Allocate component node */
+ comp_node = kmalloc(sizeof(*comp_node), GFP_ATOMIC);
+ if (!comp_node) {
+ err = -ENOMEM;
+ goto err_comp_node;
+ }
+ *comp_node = *cfg;
+
+ /* Add component node to event node */
+ list_add_tail(&comp_node->l, &event_node->comp_list);
+
+ return 0;
+
+err_comp_node:
+ if (list_empty(&event_node->comp_list)) {
+ list_del(&event_node->l);
+ kfree(event_node);
+ }
+ return err;
+}
+
+static int counter_set_watch(struct counter_device *const counter,
+ const unsigned long arg)
+{
+ void __user *const uwatch = (void __user *)arg;
+ struct counter_watch watch;
+ struct counter_comp_node comp_node;
+ size_t parent, id;
+ struct counter_comp *ext;
+ size_t num_ext;
+
+ if (copy_from_user(&watch, uwatch, sizeof(watch)))
+ return -EFAULT;
+ parent = watch.component.parent;
+ id = watch.component.id;
+
+ /* Configure parent component info for comp node */
+ switch (watch.component.scope) {
+ case COUNTER_SCOPE_DEVICE:
+ comp_node.parent = NULL;
+
+ ext = counter->ext;
+ num_ext = counter->num_ext;
+ break;
+ case COUNTER_SCOPE_SIGNAL:
+ if (counter->num_signals < parent + 1)
+ return -EINVAL;
+
+ comp_node.parent = counter->signals + parent;
+
+ ext = counter->signals[parent].ext;
+ num_ext = counter->signals[parent].num_ext;
+ break;
+ case COUNTER_SCOPE_COUNT:
+ if (counter->num_counts < parent + 1)
+ return -EINVAL;
+
+ comp_node.parent = counter->counts + parent;
+
+ ext = counter->counts[parent].ext;
+ num_ext = counter->counts[parent].num_ext;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ /* Configure component info for comp node */
+ switch (watch.component.type) {
+ case COUNTER_COMPONENT_SIGNAL:
+ if (watch.component.scope != COUNTER_SCOPE_SIGNAL)
+ return -EINVAL;
+
+ comp_node.comp.type = COUNTER_COMP_SIGNAL_LEVEL;
+ comp_node.comp.signal_u8_read = counter->ops->signal_read;
+ break;
+ case COUNTER_COMPONENT_COUNT:
+ if (watch.component.scope != COUNTER_SCOPE_COUNT)
+ return -EINVAL;
+
+ comp_node.comp.type = COUNTER_COMP_U64;
+ comp_node.comp.count_u64_read = counter->ops->count_read;
+ break;
+ case COUNTER_COMPONENT_FUNCTION:
+ if (watch.component.scope != COUNTER_SCOPE_COUNT)
+ return -EINVAL;
+
+ comp_node.comp.type = COUNTER_COMP_FUNCTION;
+ comp_node.comp.count_u8_read = counter->ops->function_read;
+ break;
+ case COUNTER_COMPONENT_SYNAPSE_ACTION:
+ if (watch.component.scope != COUNTER_SCOPE_COUNT)
+ return -EINVAL;
+ if (counter->counts[parent].num_synapses < id + 1)
+ return -EINVAL;
+
+ comp_node.comp.type = COUNTER_COMP_SYNAPSE_ACTION;
+ comp_node.comp.action_read = counter->ops->action_read;
+ comp_node.comp.priv = counter->counts[parent].synapses + id;
+ break;
+ case COUNTER_COMPONENT_EXTENSION:
+ if (num_ext < id + 1)
+ return -EINVAL;
+
+ comp_node.comp = ext[id];
+ break;
+ default:
+ return -EINVAL;
+ }
+ if (!comp_node.comp.count_u8_read)
+ return -EFAULT;
+ comp_node.component = watch.component;
+
+ return counter_set_event_node(counter, &watch, &comp_node);
+}
+
+static long counter_chrdev_ioctl(struct file *filp, unsigned int cmd,
+ unsigned long arg)
+{
+ struct counter_device *const counter = filp->private_data;
+ raw_spinlock_t *const events_lock = &counter->events_lock;
+ unsigned long flags;
+ struct list_head *const events_list = &counter->events_list;
+ struct list_head *const next_events_list = &counter->next_events_list;
+
+ switch (cmd) {
+ case COUNTER_CLEAR_WATCHES_IOCTL:
+ raw_spin_lock_irqsave(events_lock, flags);
+ counter_events_list_free(events_list);
+ raw_spin_unlock_irqrestore(events_lock, flags);
+ counter_events_list_free(next_events_list);
+ break;
+ case COUNTER_SET_WATCH_IOCTL:
+ return counter_set_watch(counter, arg);
+ case COUNTER_LOAD_WATCHES_IOCTL:
+ raw_spin_lock_irqsave(events_lock, flags);
+ counter_events_list_free(events_list);
+ list_replace_init(next_events_list, events_list);
+ raw_spin_unlock_irqrestore(events_lock, flags);
+ break;
+ default:
+ return -ENOIOCTLCMD;
+ }
+
+ return 0;
+}
+
+static int counter_chrdev_open(struct inode *inode, struct file *filp)
+{
+ struct counter_device *const counter = container_of(inode->i_cdev,
+ typeof(*counter),
+ chrdev);
+
+ get_device(&counter->dev);
+ filp->private_data = counter;
+
+ return nonseekable_open(inode, filp);
+}
+
+static int counter_chrdev_release(struct inode *inode, struct file *filp)
+{
+ struct counter_device *const counter = filp->private_data;
+ unsigned long flags;
+
+ put_device(&counter->dev);
+
+ raw_spin_lock_irqsave(&counter->events_lock, flags);
+ counter_events_list_free(&counter->events_list);
+ raw_spin_unlock_irqrestore(&counter->events_lock, flags);
+ counter_events_list_free(&counter->next_events_list);
+
+ return 0;
+}
+
+static const struct file_operations counter_fops = {
+ .llseek = no_llseek,
+ .read = counter_chrdev_read,
+ .poll = counter_chrdev_poll,
+ .unlocked_ioctl = counter_chrdev_ioctl,
+ .open = counter_chrdev_open,
+ .release = counter_chrdev_release,
+};
+
+int counter_chrdev_add(struct counter_device *const counter,
+ const dev_t counter_devt)
+{
+ struct device *const dev = &counter->dev;
+ struct cdev *const chrdev = &counter->chrdev;
+
+ /* Initialize Counter events lists */
+ INIT_LIST_HEAD(&counter->events_list);
+ INIT_LIST_HEAD(&counter->next_events_list);
+ raw_spin_lock_init(&counter->events_lock);
+
+ /* Initialize Counter events queue */
+ INIT_KFIFO(counter->events);
+ init_waitqueue_head(&counter->events_wait);
+
+ /* Initialize character device */
+ cdev_init(chrdev, &counter_fops);
+ dev->devt = MKDEV(MAJOR(counter_devt), counter->id);
+ cdev_set_parent(chrdev, &dev->kobj);
+
+ return cdev_add(chrdev, dev->devt, 1);
+}
+
+void counter_chrdev_remove(struct counter_device *const counter)
+{
+ cdev_del(&counter->chrdev);
+}
+
+static int counter_get_data(struct counter_device *const counter,
+ const struct counter_comp_node *const comp_node,
+ void *const value)
+{
+ const struct counter_comp *const comp = &comp_node->comp;
+ void *const parent = comp_node->parent;
+
+ switch (comp->type) {
+ case COUNTER_COMP_U8:
+ case COUNTER_COMP_BOOL:
+ case COUNTER_COMP_SIGNAL_LEVEL:
+ case COUNTER_COMP_FUNCTION:
+ case COUNTER_COMP_ENUM:
+ case COUNTER_COMP_COUNT_DIRECTION:
+ case COUNTER_COMP_COUNT_MODE:
+ switch (comp_node->component.scope) {
+ case COUNTER_SCOPE_DEVICE:
+ return comp->device_u8_read(counter, value);
+ case COUNTER_SCOPE_SIGNAL:
+ return comp->signal_u8_read(counter, parent, value);
+ case COUNTER_SCOPE_COUNT:
+ return comp->count_u8_read(counter, parent, value);
+ }
+ break;
+ case COUNTER_COMP_U64:
+ switch (comp_node->component.scope) {
+ case COUNTER_SCOPE_DEVICE:
+ return comp->device_u64_read(counter, value);
+ case COUNTER_SCOPE_SIGNAL:
+ return comp->signal_u64_read(counter, parent, value);
+ case COUNTER_SCOPE_COUNT:
+ return comp->count_u64_read(counter, parent, value);
+ }
+ break;
+ case COUNTER_COMP_SYNAPSE_ACTION:
+ return comp->action_read(counter, parent, comp->priv, value);
+ }
+
+ return 0;
+}
+
+/**
+ * counter_push_event - queue event for userspace reading
+ * @counter: pointer to Counter structure
+ * @event: triggered event
+ * @channel: event channel
+ *
+ * Note: If no one is watching for the respective event, it is silently
+ * discarded.
+ *
+ * RETURNS:
+ * 0 on success, negative error number on failure.
+ */
+int counter_push_event(struct counter_device *const counter, const u8 event,
+ const u8 channel)
+{
+ struct counter_event ev = {0};
+ unsigned int copied = 0;
+ unsigned long flags;
+ struct counter_event_node *event_node;
+ struct counter_comp_node *comp_node;
+ int err;
+
+ ev.timestamp = ktime_get_ns();
+ ev.watch.event = event;
+ ev.watch.channel = channel;
+
+ raw_spin_lock_irqsave(&counter->events_lock, flags);
+
+ /* Search for event in the list */
+ list_for_each_entry(event_node, &counter->events_list, l)
+ if (event_node->event == event &&
+ event_node->channel == channel)
+ break;
+
+ /* If event is not in the list */
+ if (&event_node->l == &counter->events_list)
+ goto exit_early;
+
+ /* Read and queue relevant comp for userspace */
+ list_for_each_entry(comp_node, &event_node->comp_list, l) {
+ err = counter_get_data(counter, comp_node, &ev.value_u8);
+ if (err)
+ goto err_counter_get_data;
+
+ ev.watch.component = comp_node->component;
+
+ copied += kfifo_put(&counter->events, ev);
+ }
+
+ if (copied)
+ wake_up_poll(&counter->events_wait, EPOLLIN);
+
+exit_early:
+ raw_spin_unlock_irqrestore(&counter->events_lock, flags);
+
+ return 0;
+
+err_counter_get_data:
+ raw_spin_unlock_irqrestore(&counter->events_lock, flags);
+ return err;
+}
+EXPORT_SYMBOL_GPL(counter_push_event);
diff --git a/drivers/counter/counter-chrdev.h b/drivers/counter/counter-chrdev.h
new file mode 100644
index 000000000000..cf5a318fe540
--- /dev/null
+++ b/drivers/counter/counter-chrdev.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Counter character device interface
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+#ifndef _COUNTER_CHRDEV_H_
+#define _COUNTER_CHRDEV_H_
+
+#include <linux/counter.h>
+#include <linux/types.h>
+
+int counter_chrdev_add(struct counter_device *const counter,
+ const dev_t counter_devt);
+void counter_chrdev_remove(struct counter_device *const counter);
+
+#endif /* _COUNTER_CHRDEV_H_ */
diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
index 987c6e8277eb..e9c01de36fcf 100644
--- a/drivers/counter/counter-core.c
+++ b/drivers/counter/counter-core.c
@@ -5,12 +5,16 @@
*/
#include <linux/counter.h>
#include <linux/device.h>
+#include <linux/device/bus.h>
#include <linux/export.h>
+#include <linux/fs.h>
#include <linux/gfp.h>
#include <linux/idr.h>
#include <linux/init.h>
#include <linux/module.h>
+#include <linux/types.h>

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

/* Provides a unique ID for each counter device */
@@ -32,6 +36,8 @@ static struct bus_type counter_bus_type = {
.name = "counter"
};

+static dev_t counter_devt;
+
/**
* counter_register - register Counter to the system
* @counter: pointer to Counter to register
@@ -50,7 +56,6 @@ int counter_register(struct counter_device *const counter)
if (counter->id < 0)
return counter->id;

- /* Configure device structure for Counter */
dev->type = &counter_device_type;
dev->bus = &counter_bus_type;
if (counter->parent) {
@@ -61,20 +66,27 @@ int counter_register(struct counter_device *const counter)
device_initialize(dev);
dev_set_drvdata(dev, counter);

+ /* Add Counter character device */
+ err = counter_chrdev_add(counter, counter_devt);
+ if (err)
+ goto err_free_id;
+
/* Add Counter sysfs attributes */
err = counter_sysfs_add(counter);
if (err)
- goto err_free_id;
+ goto err_remove_chrdev;

/* Add device to system */
err = device_add(dev);
if (err) {
put_device(dev);
- goto err_free_id;
+ goto err_remove_chrdev;
}

return 0;

+err_remove_chrdev:
+ counter_chrdev_remove(counter);
err_free_id:
/* get_device/put_device combo used to free managed resources */
get_device(dev);
@@ -96,6 +108,7 @@ void counter_unregister(struct counter_device *const counter)
return;

device_unregister(&counter->dev);
+ counter_chrdev_remove(counter);
}
EXPORT_SYMBOL_GPL(counter_unregister);

@@ -142,13 +155,30 @@ int devm_counter_register(struct device *dev,
}
EXPORT_SYMBOL_GPL(devm_counter_register);

+#define COUNTER_DEV_MAX 256
+
static int __init counter_init(void)
{
- return bus_register(&counter_bus_type);
+ int err;
+
+ err = bus_register(&counter_bus_type);
+ if (err < 0)
+ return err;
+
+ err = alloc_chrdev_region(&counter_devt, 0, COUNTER_DEV_MAX, "counter");
+ if (err < 0)
+ goto err_unregister_bus;
+
+ return 0;
+
+err_unregister_bus:
+ bus_unregister(&counter_bus_type);
+ return err;
}

static void __exit counter_exit(void)
{
+ unregister_chrdev_region(counter_devt, COUNTER_DEV_MAX);
bus_unregister(&counter_bus_type);
}

diff --git a/drivers/counter/counter-sysfs.c b/drivers/counter/counter-sysfs.c
index e66ed99dd5ea..cefef61f170d 100644
--- a/drivers/counter/counter-sysfs.c
+++ b/drivers/counter/counter-sysfs.c
@@ -434,6 +434,7 @@ static ssize_t counter_comp_name_show(struct device *dev,

static int counter_name_attr_create(struct device *const dev,
struct counter_attribute_group *const group,
+ const char *const attr_name,
const char *const name)
{
struct counter_attribute *counter_attr;
@@ -448,7 +449,7 @@ static int counter_name_attr_create(struct device *const dev,

/* Configure device attribute */
sysfs_attr_init(&counter_attr->dev_attr.attr);
- counter_attr->dev_attr.attr.name = "name";
+ counter_attr->dev_attr.attr.name = attr_name;
counter_attr->dev_attr.attr.mode = 0444;
counter_attr->dev_attr.show = counter_comp_name_show;

@@ -459,6 +460,76 @@ static int counter_name_attr_create(struct device *const dev,
return 0;
}

+static ssize_t counter_comp_width_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ switch (to_counter_attribute(attr)->comp.type) {
+ case COUNTER_COMP_U8:
+ case COUNTER_COMP_BOOL:
+ case COUNTER_COMP_SIGNAL_LEVEL:
+ case COUNTER_COMP_FUNCTION:
+ case COUNTER_COMP_SYNAPSE_ACTION:
+ case COUNTER_COMP_ENUM:
+ case COUNTER_COMP_COUNT_DIRECTION:
+ case COUNTER_COMP_COUNT_MODE:
+ return sprintf(buf, "8\n");
+ case COUNTER_COMP_U64:
+ return sprintf(buf, "64\n");
+ }
+
+ return 0;
+}
+
+static int counter_ext_width_attr_create(struct device *const dev,
+ struct counter_attribute_group *const group, const size_t i,
+ const struct counter_comp *const ext)
+{
+ struct counter_attribute *counter_attr;
+ const char *name;
+
+ /* Allocate Counter attribute */
+ counter_attr = devm_kzalloc(dev, sizeof(*counter_attr), GFP_KERNEL);
+ if (!counter_attr)
+ return -ENOMEM;
+
+ /* Generate attribute name */
+ name = devm_kasprintf(dev, GFP_KERNEL, "extension%zu_width", i);
+ if (!name)
+ return -ENOMEM;
+
+ /* Configure Counter attribute */
+ counter_attr->comp.type = ext->type;
+
+ /* Configure device attribute */
+ sysfs_attr_init(&counter_attr->dev_attr.attr);
+ counter_attr->dev_attr.attr.name = name;
+ counter_attr->dev_attr.attr.mode = 0444;
+ counter_attr->dev_attr.show = counter_comp_width_show;
+
+ /* Store list node */
+ list_add(&counter_attr->l, &group->attr_list);
+ group->num_attr++;
+
+ return 0;
+}
+
+static int counter_ext_meta_attrs_create(struct device *const dev,
+ struct counter_attribute_group *const group, const size_t i,
+ const struct counter_comp *const ext)
+{
+ const char *attr_name;
+ int err;
+
+ attr_name = devm_kasprintf(dev, GFP_KERNEL, "extension%zu_name", i);
+ if (!attr_name)
+ return -ENOMEM;
+
+ err = counter_name_attr_create(dev, group, attr_name, ext->name);
+ if (err)
+ return err;
+
+ return counter_ext_width_attr_create(dev, group, i, ext);
+}

static struct counter_comp counter_signal_comp = {
.type = COUNTER_COMP_SIGNAL_LEVEL,
@@ -474,6 +545,7 @@ static int counter_signal_attrs_create(struct counter_device *const counter,
int err;
struct counter_comp comp;
size_t i;
+ struct counter_comp *ext;

/* Create main Signal attribute */
comp = counter_signal_comp;
@@ -483,14 +555,19 @@ static int counter_signal_attrs_create(struct counter_device *const counter,
return err;

/* Create Signal name attribute */
- err = counter_name_attr_create(dev, group, signal->name);
+ err = counter_name_attr_create(dev, group, "name", signal->name);
if (err)
return err;

/* Create an attribute for each extension */
for (i = 0; i < signal->num_ext; i++) {
- err = counter_attr_create(dev, group, signal->ext + i, scope,
- signal);
+ ext = signal->ext + i;
+
+ err = counter_attr_create(dev, group, ext, scope, signal);
+ if (err)
+ return err;
+
+ err = counter_ext_meta_attrs_create(dev, group, i, ext);
if (err)
return err;
}
@@ -575,6 +652,7 @@ static int counter_count_attrs_create(struct counter_device *const counter,
int err;
struct counter_comp comp;
size_t i;
+ struct counter_comp *ext;

/* Create main Count attribute */
comp = counter_count_comp;
@@ -585,7 +663,7 @@ static int counter_count_attrs_create(struct counter_device *const counter,
return err;

/* Create Count name attribute */
- err = counter_name_attr_create(dev, group, count->name);
+ err = counter_name_attr_create(dev, group, "name", count->name);
if (err)
return err;

@@ -599,8 +677,13 @@ static int counter_count_attrs_create(struct counter_device *const counter,

/* Create an attribute for each extension */
for (i = 0; i < count->num_ext; i++) {
- err = counter_attr_create(dev, group, count->ext + i, scope,
- count);
+ ext = count->ext + i;
+
+ err = counter_attr_create(dev, group, ext, scope, count);
+ if (err)
+ return err;
+
+ err = counter_ext_meta_attrs_create(dev, group, i, ext);
if (err)
return err;
}
@@ -664,6 +747,7 @@ static int counter_device_register(struct counter_device *const counter,
struct device *const dev = &counter->dev;
int err;
size_t i;
+ struct counter_comp *ext;

/* Register Signals */
err = counter_signals_register(counter, group);
@@ -678,7 +762,7 @@ static int counter_device_register(struct counter_device *const counter,
group += counter->num_counts;

/* Create name attribute */
- err = counter_name_attr_create(dev, group, counter->name);
+ err = counter_name_attr_create(dev, group, "name", counter->name);
if (err)
return err;

@@ -696,8 +780,13 @@ static int counter_device_register(struct counter_device *const counter,

/* Create an attribute for each extension */
for (i = 0; i < counter->num_ext; i++) {
- err = counter_attr_create(dev, group, counter->ext + i, scope,
- NULL);
+ ext = counter->ext + i;
+
+ err = counter_attr_create(dev, group, ext, scope, NULL);
+ if (err)
+ return err;
+
+ err = counter_ext_meta_attrs_create(dev, group, i, ext);
if (err)
return err;
}
diff --git a/include/linux/counter.h b/include/linux/counter.h
index 132bfecca5c3..25d79047c9fc 100644
--- a/include/linux/counter.h
+++ b/include/linux/counter.h
@@ -6,10 +6,15 @@
#ifndef _COUNTER_H_
#define _COUNTER_H_

+#include <linux/cdev.h>
#include <linux/device.h>
#include <linux/kernel.h>
+#include <linux/kfifo.h>
#include <linux/list.h>
+#include <linux/spinlock_types.h>
#include <linux/types.h>
+#include <linux/wait.h>
+#include <uapi/linux/counter.h>

struct counter_device;
struct counter_count;
@@ -28,35 +33,6 @@ enum counter_comp_type {
COUNTER_COMP_COUNT_MODE,
};

-#define COUNTER_SCOPE_DEVICE 0
-#define COUNTER_SCOPE_SIGNAL 1
-#define COUNTER_SCOPE_COUNT 2
-
-#define COUNTER_COUNT_DIRECTION_FORWARD 0
-#define COUNTER_COUNT_DIRECTION_BACKWARD 1
-
-#define COUNTER_COUNT_MODE_NORMAL 0
-#define COUNTER_COUNT_MODE_RANGE_LIMIT 1
-#define COUNTER_COUNT_MODE_NON_RECYCLE 2
-#define COUNTER_COUNT_MODE_MODULO_N 3
-
-#define COUNTER_FUNCTION_INCREASE 0
-#define COUNTER_FUNCTION_DECREASE 1
-#define COUNTER_FUNCTION_PULSE_DIRECTION 2
-#define COUNTER_FUNCTION_QUADRATURE_X1_A 3
-#define COUNTER_FUNCTION_QUADRATURE_X1_B 4
-#define COUNTER_FUNCTION_QUADRATURE_X2_A 5
-#define COUNTER_FUNCTION_QUADRATURE_X2_B 6
-#define COUNTER_FUNCTION_QUADRATURE_X4 7
-
-#define COUNTER_SIGNAL_LEVEL_LOW 0
-#define COUNTER_SIGNAL_LEVEL_HIGH 1
-
-#define COUNTER_SYNAPSE_ACTION_NONE 0
-#define COUNTER_SYNAPSE_ACTION_RISING_EDGE 1
-#define COUNTER_SYNAPSE_ACTION_FALLING_EDGE 2
-#define COUNTER_SYNAPSE_ACTION_BOTH_EDGES 3
-
struct counter_comp {
enum counter_comp_type type;
const char *name;
@@ -205,6 +181,12 @@ struct counter_ops {
* @priv: optional private data supplied by driver
* @id: unique ID used to identify the Counter
* @dev: internal device structure
+ * @chrdev: internal character device structure
+ * @events_lock: synchronization lock for Counter events
+ * @events_list: list of current watching Counter events
+ * @next_events_list: list of next watching Counter events
+ * @events: queue of detected Counter events
+ * @events_wait: wait queue to allow blocking reads of Counter events
*/
struct counter_device {
const char *name;
@@ -224,6 +206,12 @@ struct counter_device {

int id;
struct device dev;
+ struct cdev chrdev;
+ raw_spinlock_t events_lock;
+ struct list_head events_list;
+ struct list_head next_events_list;
+ DECLARE_KFIFO(events, struct counter_event, 64);
+ wait_queue_head_t events_wait;
};

int counter_register(struct counter_device *const counter);
@@ -232,6 +220,8 @@ int devm_counter_register(struct device *dev,
struct counter_device *const counter);
void devm_counter_unregister(struct device *dev,
struct counter_device *const counter);
+int counter_push_event(struct counter_device *const counter, const u8 event,
+ const u8 channel);

#define COUNTER_COMP_DEVICE_U8(_name, _read, _write) \
{ \
diff --git a/include/uapi/linux/counter.h b/include/uapi/linux/counter.h
new file mode 100644
index 000000000000..ad9a8686b2b0
--- /dev/null
+++ b/include/uapi/linux/counter.h
@@ -0,0 +1,99 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Userspace ABI for Counter character devices
+ * Copyright (C) 2020 William Breathitt Gray
+ */
+#ifndef _UAPI_COUNTER_H_
+#define _UAPI_COUNTER_H_
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+#define COUNTER_SCOPE_DEVICE 0
+#define COUNTER_SCOPE_SIGNAL 1
+#define COUNTER_SCOPE_COUNT 2
+
+#define COUNTER_COMPONENT_SIGNAL 0
+#define COUNTER_COMPONENT_COUNT 1
+#define COUNTER_COMPONENT_FUNCTION 2
+#define COUNTER_COMPONENT_SYNAPSE_ACTION 3
+#define COUNTER_COMPONENT_EXTENSION 4
+
+/**
+ * struct counter_component - Counter component identification
+ * @scope: component scope (Device, Count, or Signal)
+ * @parent: parent component identification number
+ * @type: component type (Count, extension, etc.)
+ * @id: component identification number
+ */
+struct counter_component {
+ __u8 scope;
+ __u64 parent;
+ __u8 type;
+ __u64 id;
+};
+
+#define COUNTER_EVENT_OVERFLOW 0
+#define COUNTER_EVENT_UNDERFLOW 1
+#define COUNTER_EVENT_OVERFLOW_UNDERFLOW 2
+#define COUNTER_EVENT_THRESHOLD 3
+#define COUNTER_EVENT_INDEX 4
+
+/**
+ * struct counter_watch - Counter component watch configuration
+ * @event: event that triggers
+ * @channel: event channel
+ * @component: component to watch when event triggers
+ */
+struct counter_watch {
+ __u8 event;
+ __u8 channel;
+ struct counter_component component;
+};
+
+#define COUNTER_CLEAR_WATCHES_IOCTL _IO(0x3E, 0x00)
+#define COUNTER_SET_WATCH_IOCTL _IOW(0x3E, 0x01, struct counter_watch)
+#define COUNTER_LOAD_WATCHES_IOCTL _IO(0x3E, 0x02)
+
+/**
+ * struct counter_event - Counter event data
+ * @timestamp: best estimate of time of event occurrence, in nanoseconds
+ * @watch: component watch configuration
+ * @value_u8: component value as __u8 data type
+ * @value_u64: component value as __u64 data type
+ */
+struct counter_event {
+ __u64 timestamp;
+ struct counter_watch watch;
+ union {
+ __u8 value_u8;
+ __u64 value_u64;
+ };
+};
+
+#define COUNTER_COUNT_DIRECTION_FORWARD 0
+#define COUNTER_COUNT_DIRECTION_BACKWARD 1
+
+#define COUNTER_COUNT_MODE_NORMAL 0
+#define COUNTER_COUNT_MODE_RANGE_LIMIT 1
+#define COUNTER_COUNT_MODE_NON_RECYCLE 2
+#define COUNTER_COUNT_MODE_MODULO_N 3
+
+#define COUNTER_FUNCTION_INCREASE 0
+#define COUNTER_FUNCTION_DECREASE 1
+#define COUNTER_FUNCTION_PULSE_DIRECTION 2
+#define COUNTER_FUNCTION_QUADRATURE_X1_A 3
+#define COUNTER_FUNCTION_QUADRATURE_X1_B 4
+#define COUNTER_FUNCTION_QUADRATURE_X2_A 5
+#define COUNTER_FUNCTION_QUADRATURE_X2_B 6
+#define COUNTER_FUNCTION_QUADRATURE_X4 7
+
+#define COUNTER_SIGNAL_LEVEL_LOW 0
+#define COUNTER_SIGNAL_LEVEL_HIGH 1
+
+#define COUNTER_SYNAPSE_ACTION_NONE 0
+#define COUNTER_SYNAPSE_ACTION_RISING_EDGE 1
+#define COUNTER_SYNAPSE_ACTION_FALLING_EDGE 2
+#define COUNTER_SYNAPSE_ACTION_BOTH_EDGES 3
+
+#endif /* _UAPI_COUNTER_H_ */
--
2.28.0