// 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, .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", [GNSS_TYPE_MTK] = "MTK", }; 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");