1 files changed, 420 insertions, 0 deletions
diff --git a/drivers/gnss/core.c b/drivers/gnss/core.c
new file mode 100644
index 000000000000..4291a0dd22aa
--- /dev/null
+++ b/drivers/gnss/core.c
@@ -0,0 +1,420 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * GNSS receiver core
+ *
+ * Copyright (C) 2018 Johan Hovold <johan@kernel.org>
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/cdev.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/gnss.h>
+#include <linux/idr.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/poll.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/wait.h>
+
+#define GNSS_FLAG_HAS_WRITE_RAW		BIT(0)
+
+#define GNSS_MINORS	16
+
+static DEFINE_IDA(gnss_minors);
+static dev_t gnss_first;
+
+/* FIFO size must be a power of two */
+#define GNSS_READ_FIFO_SIZE	4096
+#define GNSS_WRITE_BUF_SIZE	1024
+
+#define to_gnss_device(d) container_of((d), struct gnss_device, dev)
+
+static int gnss_open(struct inode *inode, struct file *file)
+{
+	struct gnss_device *gdev;
+	int ret = 0;
+
+	gdev = container_of(inode->i_cdev, struct gnss_device, cdev);
+
+	get_device(&gdev->dev);
+
+	nonseekable_open(inode, file);
+	file->private_data = gdev;
+
+	down_write(&gdev->rwsem);
+	if (gdev->disconnected) {
+		ret = -ENODEV;
+		goto unlock;
+	}
+
+	if (gdev->count++ == 0) {
+		ret = gdev->ops->open(gdev);
+		if (ret)
+			gdev->count--;
+	}
+unlock:
+	up_write(&gdev->rwsem);
+
+	if (ret)
+		put_device(&gdev->dev);
+
+	return ret;
+}
+
+static int gnss_release(struct inode *inode, struct file *file)
+{
+	struct gnss_device *gdev = file->private_data;
+
+	down_write(&gdev->rwsem);
+	if (gdev->disconnected)
+		goto unlock;
+
+	if (--gdev->count == 0) {
+		gdev->ops->close(gdev);
+		kfifo_reset(&gdev->read_fifo);
+	}
+unlock:
+	up_write(&gdev->rwsem);
+
+	put_device(&gdev->dev);
+
+	return 0;
+}
+
+static ssize_t gnss_read(struct file *file, char __user *buf,
+				size_t count, loff_t *pos)
+{
+	struct gnss_device *gdev = file->private_data;
+	unsigned int copied;
+	int ret;
+
+	mutex_lock(&gdev->read_mutex);
+	while (kfifo_is_empty(&gdev->read_fifo)) {
+		mutex_unlock(&gdev->read_mutex);
+
+		if (gdev->disconnected)
+			return 0;
+
+		if (file->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+
+		ret = wait_event_interruptible(gdev->read_queue,
+				gdev->disconnected ||
+				!kfifo_is_empty(&gdev->read_fifo));
+		if (ret)
+			return -ERESTARTSYS;
+
+		mutex_lock(&gdev->read_mutex);
+	}
+
+	ret = kfifo_to_user(&gdev->read_fifo, buf, count, &copied);
+	if (ret == 0)
+		ret = copied;
+
+	mutex_unlock(&gdev->read_mutex);
+
+	return ret;
+}
+
+static ssize_t gnss_write(struct file *file, const char __user *buf,
+				size_t count, loff_t *pos)
+{
+	struct gnss_device *gdev = file->private_data;
+	size_t written = 0;
+	int ret;
+
+	if (gdev->disconnected)
+		return -EIO;
+
+	if (!count)
+		return 0;
+
+	if (!(gdev->flags & GNSS_FLAG_HAS_WRITE_RAW))
+		return -EIO;
+
+	/* Ignoring O_NONBLOCK, write_raw() is synchronous. */
+
+	ret = mutex_lock_interruptible(&gdev->write_mutex);
+	if (ret)
+		return -ERESTARTSYS;
+
+	for (;;) {
+		size_t n = count - written;
+
+		if (n > GNSS_WRITE_BUF_SIZE)
+			n = GNSS_WRITE_BUF_SIZE;
+
+		if (copy_from_user(gdev->write_buf, buf, n)) {
+			ret = -EFAULT;
+			goto out_unlock;
+		}
+
+		/*
+		 * Assumes write_raw can always accept GNSS_WRITE_BUF_SIZE
+		 * bytes.
+		 *
+		 * FIXME: revisit
+		 */
+		down_read(&gdev->rwsem);
+		if (!gdev->disconnected)
+			ret = gdev->ops->write_raw(gdev, gdev->write_buf, n);
+		else
+			ret = -EIO;
+		up_read(&gdev->rwsem);
+
+		if (ret < 0)
+			break;
+
+		written += ret;
+		buf += ret;
+
+		if (written == count)
+			break;
+	}
+
+	if (written)
+		ret = written;
+out_unlock:
+	mutex_unlock(&gdev->write_mutex);
+
+	return ret;
+}
+
+static __poll_t gnss_poll(struct file *file, poll_table *wait)
+{
+	struct gnss_device *gdev = file->private_data;
+	__poll_t mask = 0;
+
+	poll_wait(file, &gdev->read_queue, wait);
+
+	if (!kfifo_is_empty(&gdev->read_fifo))
+		mask |= EPOLLIN | EPOLLRDNORM;
+	if (gdev->disconnected)
+		mask |= EPOLLHUP;
+
+	return mask;
+}
+
+static const struct file_operations gnss_fops = {
+	.owner		= THIS_MODULE,
+	.open		= gnss_open,
+	.release	= gnss_release,
+	.read		= gnss_read,
+	.write		= gnss_write,
+	.poll		= gnss_poll,
+	.llseek		= no_llseek,
+};
+
+static struct class *gnss_class;
+
+static void gnss_device_release(struct device *dev)
+{
+	struct gnss_device *gdev = to_gnss_device(dev);
+
+	kfree(gdev->write_buf);
+	kfifo_free(&gdev->read_fifo);
+	ida_simple_remove(&gnss_minors, gdev->id);
+	kfree(gdev);
+}
+
+struct gnss_device *gnss_allocate_device(struct device *parent)
+{
+	struct gnss_device *gdev;
+	struct device *dev;
+	int id;
+	int ret;
+
+	gdev = kzalloc(sizeof(*gdev), GFP_KERNEL);
+	if (!gdev)
+		return NULL;
+
+	id = ida_simple_get(&gnss_minors, 0, GNSS_MINORS, GFP_KERNEL);
+	if (id < 0) {
+		kfree(gdev);
+		return NULL;
+	}
+
+	gdev->id = id;
+
+	dev = &gdev->dev;
+	device_initialize(dev);
+	dev->devt = gnss_first + id;
+	dev->class = gnss_class;
+	dev->parent = parent;
+	dev->release = gnss_device_release;
+	dev_set_drvdata(dev, gdev);
+	dev_set_name(dev, "gnss%d", id);
+
+	init_rwsem(&gdev->rwsem);
+	mutex_init(&gdev->read_mutex);
+	mutex_init(&gdev->write_mutex);
+	init_waitqueue_head(&gdev->read_queue);
+
+	ret = kfifo_alloc(&gdev->read_fifo, GNSS_READ_FIFO_SIZE, GFP_KERNEL);
+	if (ret)
+		goto err_put_device;
+
+	gdev->write_buf = kzalloc(GNSS_WRITE_BUF_SIZE, GFP_KERNEL);
+	if (!gdev->write_buf)
+		goto err_put_device;
+
+	cdev_init(&gdev->cdev, &gnss_fops);
+	gdev->cdev.owner = THIS_MODULE;
+
+	return gdev;
+
+err_put_device:
+	put_device(dev);
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(gnss_allocate_device);
+
+void gnss_put_device(struct gnss_device *gdev)
+{
+	put_device(&gdev->dev);
+}
+EXPORT_SYMBOL_GPL(gnss_put_device);
+
+int gnss_register_device(struct gnss_device *gdev)
+{
+	int ret;
+
+	/* Set a flag which can be accessed without holding the rwsem. */
+	if (gdev->ops->write_raw != NULL)
+		gdev->flags |= GNSS_FLAG_HAS_WRITE_RAW;
+
+	ret = cdev_device_add(&gdev->cdev, &gdev->dev);
+	if (ret) {
+		dev_err(&gdev->dev, "failed to add device: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gnss_register_device);
+
+void gnss_deregister_device(struct gnss_device *gdev)
+{
+	down_write(&gdev->rwsem);
+	gdev->disconnected = true;
+	if (gdev->count) {
+		wake_up_interruptible(&gdev->read_queue);
+		gdev->ops->close(gdev);
+	}
+	up_write(&gdev->rwsem);
+
+	cdev_device_del(&gdev->cdev, &gdev->dev);
+}
+EXPORT_SYMBOL_GPL(gnss_deregister_device);
+
+/*
+ * Caller guarantees serialisation.
+ *
+ * Must not be called for a closed device.
+ */
+int gnss_insert_raw(struct gnss_device *gdev, const unsigned char *buf,
+				size_t count)
+{
+	int ret;
+
+	ret = kfifo_in(&gdev->read_fifo, buf, count);
+
+	wake_up_interruptible(&gdev->read_queue);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gnss_insert_raw);
+
+static const char * const gnss_type_names[GNSS_TYPE_COUNT] = {
+	[GNSS_TYPE_NMEA]	= "NMEA",
+	[GNSS_TYPE_SIRF]	= "SiRF",
+	[GNSS_TYPE_UBX]		= "UBX",
+};
+
+static const char *gnss_type_name(struct gnss_device *gdev)
+{
+	const char *name = NULL;
+
+	if (gdev->type < GNSS_TYPE_COUNT)
+		name = gnss_type_names[gdev->type];
+
+	if (!name)
+		dev_WARN(&gdev->dev, "type name not defined\n");
+
+	return name;
+}
+
+static ssize_t type_show(struct device *dev, struct device_attribute *attr,
+				char *buf)
+{
+	struct gnss_device *gdev = to_gnss_device(dev);
+
+	return sprintf(buf, "%s\n", gnss_type_name(gdev));
+}
+static DEVICE_ATTR_RO(type);
+
+static struct attribute *gnss_attrs[] = {
+	&dev_attr_type.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(gnss);
+
+static int gnss_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	struct gnss_device *gdev = to_gnss_device(dev);
+	int ret;
+
+	ret = add_uevent_var(env, "GNSS_TYPE=%s", gnss_type_name(gdev));
+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int __init gnss_module_init(void)
+{
+	int ret;
+
+	ret = alloc_chrdev_region(&gnss_first, 0, GNSS_MINORS, "gnss");
+	if (ret < 0) {
+		pr_err("failed to allocate device numbers: %d\n", ret);
+		return ret;
+	}
+
+	gnss_class = class_create(THIS_MODULE, "gnss");
+	if (IS_ERR(gnss_class)) {
+		ret = PTR_ERR(gnss_class);
+		pr_err("failed to create class: %d\n", ret);
+		goto err_unregister_chrdev;
+	}
+
+	gnss_class->dev_groups = gnss_groups;
+	gnss_class->dev_uevent = gnss_uevent;
+
+	pr_info("GNSS driver registered with major %d\n", MAJOR(gnss_first));
+
+	return 0;
+
+err_unregister_chrdev:
+	unregister_chrdev_region(gnss_first, GNSS_MINORS);
+
+	return ret;
+}
+module_init(gnss_module_init);
+
+static void __exit gnss_module_exit(void)
+{
+	class_destroy(gnss_class);
+	unregister_chrdev_region(gnss_first, GNSS_MINORS);
+	ida_destroy(&gnss_minors);
+}
+module_exit(gnss_module_exit);
+
+MODULE_AUTHOR("Johan Hovold <johan@kernel.org>");
+MODULE_DESCRIPTION("GNSS receiver core");
+MODULE_LICENSE("GPL v2");