counter: Add character device interface

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.

Cc: David Lechner <david@lechnology.com>
Cc: Gwendal Grignou <gwendal@chromium.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
Link: https://lore.kernel.org/r/b8b8c64b4065aedff43699ad1f0e2f8d1419c15b.1632884256.git.vilhelm.gray@gmail.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

1 files changed, 51 insertions, 5 deletions

diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
index 3cda2c47bacb..5acc54539623 100644
--- a/drivers/counter/counter-core.c
+++ b/drivers/counter/counter-core.c
@@ -3,14 +3,22 @@
  * Generic Counter interface
  * Copyright (C) 2020 William Breathitt Gray
  */
+#include <linux/cdev.h>
 #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/kdev_t.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/types.h>
+#include <linux/wait.h>
 
+#include "counter-chrdev.h"
 #include "counter-sysfs.h"
 
 /* Provides a unique ID for each counter device */
@@ -18,6 +26,9 @@ static DEFINE_IDA(counter_ida);
 
 static void counter_device_release(struct device *dev)
 {
+	struct counter_device *const counter = dev_get_drvdata(dev);
+
+	counter_chrdev_remove(counter);
 	ida_free(&counter_ida, dev->id);
 }
 
@@ -31,6 +42,8 @@ static struct bus_type counter_bus_type = {
 	.dev_name = "counter",
 };
 
+static dev_t counter_devt;
+
 /**
  * counter_register - register Counter to the system
  * @counter:	pointer to Counter to register
@@ -53,10 +66,13 @@ int counter_register(struct counter_device *const counter)
 	if (id < 0)
 		return id;
 
+	mutex_init(&counter->ops_exist_lock);
+
 	/* Configure device structure for Counter */
 	dev->id = id;
 	dev->type = &counter_device_type;
 	dev->bus = &counter_bus_type;
+	dev->devt = MKDEV(MAJOR(counter_devt), id);
 	if (counter->parent) {
 		dev->parent = counter->parent;
 		dev->of_node = counter->parent->of_node;
@@ -64,18 +80,22 @@ int counter_register(struct counter_device *const counter)
 	device_initialize(dev);
 	dev_set_drvdata(dev, counter);
 
-	/* Add Counter sysfs attributes */
 	err = counter_sysfs_add(counter);
 	if (err < 0)
 		goto err_free_id;
 
-	/* Add device to system */
-	err = device_add(dev);
+	err = counter_chrdev_add(counter);
 	if (err < 0)
 		goto err_free_id;
 
+	err = cdev_device_add(&counter->chrdev, dev);
+	if (err < 0)
+		goto err_remove_chrdev;
+
 	return 0;
 
+err_remove_chrdev:
+	counter_chrdev_remove(counter);
 err_free_id:
 	put_device(dev);
 	return err;
@@ -93,7 +113,16 @@ void counter_unregister(struct counter_device *const counter)
 	if (!counter)
 		return;
 
-	device_unregister(&counter->dev);
+	cdev_device_del(&counter->chrdev, &counter->dev);
+
+	mutex_lock(&counter->ops_exist_lock);
+
+	counter->ops = NULL;
+	wake_up(&counter->events_wait);
+
+	mutex_unlock(&counter->ops_exist_lock);
+
+	put_device(&counter->dev);
 }
 EXPORT_SYMBOL_GPL(counter_unregister);
 
@@ -127,13 +156,30 @@ 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);
 }