/* * userio kernel serio device emulation module * Copyright (C) 2015 Red Hat * Copyright (C) 2015 Stephen Chandler Paul * * This program is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published by * the Free Software Foundation; either version 2 of the License, or (at * your option) any later version. * * This program is distributed in the hope that it will be useful, but * WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser * General Public License for more details. */ #include #include #include #include #include #include #include #include #include #include #include #include #define USERIO_NAME "userio" #define USERIO_BUFSIZE 16 static struct miscdevice userio_misc; struct userio_device { struct serio *serio; struct mutex mutex; bool running; u8 head; u8 tail; spinlock_t buf_lock; unsigned char buf[USERIO_BUFSIZE]; wait_queue_head_t waitq; }; /** * userio_device_write - Write data from serio to a userio device in userspace * @id: The serio port for the userio device * @val: The data to write to the device */ static int userio_device_write(struct serio *id, unsigned char val) { struct userio_device *userio = id->port_data; unsigned long flags; spin_lock_irqsave(&userio->buf_lock, flags); userio->buf[userio->head] = val; userio->head = (userio->head + 1) % USERIO_BUFSIZE; if (userio->head == userio->tail) dev_warn(userio_misc.this_device, "Buffer overflowed, userio client isn't keeping up"); spin_unlock_irqrestore(&userio->buf_lock, flags); wake_up_interruptible(&userio->waitq); return 0; } static int userio_char_open(struct inode *inode, struct file *file) { struct userio_device *userio; userio = kzalloc(sizeof(*userio), GFP_KERNEL); if (!userio) return -ENOMEM; mutex_init(&userio->mutex); spin_lock_init(&userio->buf_lock); init_waitqueue_head(&userio->waitq); userio->serio = kzalloc(sizeof(*userio->serio), GFP_KERNEL); if (!userio->serio) { kfree(userio); return -ENOMEM; } userio->serio->write = userio_device_write; userio->serio->port_data = userio; file->private_data = userio; return 0; } static int userio_char_release(struct inode *inode, struct file *file) { struct userio_device *userio = file->private_data; if (userio->running) { /* * Don't free the serio port here, serio_unregister_port() * does it for us. */ serio_unregister_port(userio->serio); } else { kfree(userio->serio); } kfree(userio); return 0; } static ssize_t userio_char_read(struct file *file, char __user *user_buffer, size_t count, loff_t *ppos) { struct userio_device *userio = file->private_data; int error; size_t nonwrap_len, copylen; unsigned char buf[USERIO_BUFSIZE]; unsigned long flags; /* * By the time we get here, the data that was waiting might have * been taken by another thread. Grab the buffer lock and check if * there's still any data waiting, otherwise repeat this process * until we have data (unless the file descriptor is non-blocking * of course). */ for (;;) { spin_lock_irqsave(&userio->buf_lock, flags); nonwrap_len = CIRC_CNT_TO_END(userio->head, userio->tail, USERIO_BUFSIZE); copylen = min(nonwrap_len, count); if (copylen) { memcpy(buf, &userio->buf[userio->tail], copylen); userio->tail = (userio->tail + copylen) % USERIO_BUFSIZE; } spin_unlock_irqrestore(&userio->buf_lock, flags); if (nonwrap_len) break; /* buffer was/is empty */ if (file->f_flags & O_NONBLOCK) return -EAGAIN; /* * count == 0 is special - no IO is done but we check * for error conditions (see above). */ if (count == 0) return 0; error = wait_event_interruptible(userio->waitq, userio->head != userio->tail); if (error) return error; } if (copylen) if (copy_to_user(user_buffer, buf, copylen)) return -EFAULT; return copylen; } static ssize_t userio_char_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos) { struct userio_device *userio = file->private_data; struct userio_cmd cmd; int error; if (count != sizeof(cmd)) { dev_warn(userio_misc.this_device, "Invalid payload size\n"); return -EINVAL; } if (copy_from_user(&cmd, buffer, sizeof(cmd))) return -EFAULT; error = mutex_lock_interruptible(&userio->mutex); if (error) return error; switch (cmd.type) { case USERIO_CMD_REGISTER: if (!userio->serio->id.type) { dev_warn(userio_misc.this_device, "No port type given on /dev/userio\n"); error = -EINVAL; goto out; } if (userio->running) { dev_warn(userio_misc.this_device, "Begin command sent, but we're already running\n"); error = -EBUSY; goto out; } userio->running = true; serio_register_port(userio->serio); break; case USERIO_CMD_SET_PORT_TYPE: if (userio->running) { dev_warn(userio_misc.this_device, "Can't change port type on an already running userio instance\n"); error = -EBUSY; goto out; } userio->serio->id.type = cmd.data; break; case USERIO_CMD_SEND_INTERRUPT: if (!userio->running) { dev_warn(userio_misc.this_device, "The device must be registered before sending interrupts\n"); error = -ENODEV; goto out; } serio_interrupt(userio->serio, cmd.data, 0); break; default: error = -EOPNOTSUPP; goto out; } out: mutex_unlock(&userio->mutex); return error ?: count; } static __poll_t userio_char_poll(struct file *file, poll_table *wait) { struct userio_device *userio = file->private_data; poll_wait(file, &userio->waitq, wait); if (userio->head != userio->tail) return EPOLLIN | EPOLLRDNORM; return 0; } static const struct file_operations userio_fops = { .owner = THIS_MODULE, .open = userio_char_open, .release = userio_char_release, .read = userio_char_read, .write = userio_char_write, .poll = userio_char_poll, }; static struct miscdevice userio_misc = { .fops = &userio_fops, .minor = USERIO_MINOR, .name = USERIO_NAME, }; module_driver(userio_misc, misc_register, misc_deregister); MODULE_ALIAS_MISCDEV(USERIO_MINOR); MODULE_ALIAS("devname:" USERIO_NAME); MODULE_AUTHOR("Stephen Chandler Paul "); MODULE_DESCRIPTION("Virtual Serio Device Support"); MODULE_LICENSE("GPL");