// 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); 	stream_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,}; 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_free(&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_obj(*gdev);	if (!gdev)		return NULL; 	id = ida_alloc_max(&gnss_minors, GNSS_MINORS - 1, 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",	[GNSS_TYPE_MTK]		= "MTK",}; static const char *gnss_type_name(const 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(const struct device *dev, struct kobj_uevent_env *env){	const 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("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");