3 files changed, 300 insertions, 0 deletions

diff --git a/drivers/input/serio/Kconfig b/drivers/input/serio/Kconfig
index 200841b77edb..c3d05b4d3118 100644
--- a/drivers/input/serio/Kconfig
+++ b/drivers/input/serio/Kconfig
@@ -292,4 +292,18 @@ config SERIO_SUN4I_PS2
 	  To compile this driver as a module, choose M here: the
 	  module will be called sun4i-ps2.
 
+config USERIO
+	tristate "User space serio port driver support"
+	help
+	  Say Y here if you want to support user level drivers for serio
+	  subsystem accessible under char device 10:240 - /dev/userio. Using
+	  this facility userspace programs can implement serio ports that
+	  will be used by the standard in-kernel serio consumer drivers,
+	  such as psmouse and atkbd.
+
+	  To compile this driver as a module, choose M here: the module will be
+	  called userio.
+
+	  If you are unsure, say N.
+
 endif
diff --git a/drivers/input/serio/Makefile b/drivers/input/serio/Makefile
index c600089b7a34..2374ef9b33d7 100644
--- a/drivers/input/serio/Makefile
+++ b/drivers/input/serio/Makefile
@@ -30,3 +30,4 @@ obj-$(CONFIG_SERIO_APBPS2)	+= apbps2.o
 obj-$(CONFIG_SERIO_OLPC_APSP)	+= olpc_apsp.o
 obj-$(CONFIG_HYPERV_KEYBOARD)	+= hyperv-keyboard.o
 obj-$(CONFIG_SERIO_SUN4I_PS2)	+= sun4i-ps2.o
+obj-$(CONFIG_USERIO)		+= userio.o
diff --git a/drivers/input/serio/userio.c b/drivers/input/serio/userio.c
new file mode 100644
index 000000000000..df1fd41860ac
--- /dev/null
+++ b/drivers/input/serio/userio.c
@@ -0,0 +1,285 @@
+/*
+ * userio kernel serio device emulation module
+ * Copyright (C) 2015 Red Hat
+ * Copyright (C) 2015 Stephen Chandler Paul <thatslyude@gmail.com>
+ *
+ * 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 <linux/circ_buf.h>
+#include <linux/mutex.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/serio.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/sched.h>
+#include <linux/poll.h>
+#include <uapi/linux/userio.h>
+
+#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(struct userio_device), 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(struct 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 unsigned int 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 POLLIN | POLLRDNORM;
+
+	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,
+	.llseek		= no_llseek,
+};
+
+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 <thatslyude@gmail.com>");
+MODULE_DESCRIPTION("Virtual Serio Device Support");
+MODULE_LICENSE("GPL");