HID: uhid: introduce user-space I/O driver support for HID

This adds a dummy driver that will support user-space I/O drivers for the
HID subsystem. This allows to write transport-level drivers like USB-HID
and Bluetooth-HID in user-space.

Low-Energy Bluetooth needs this to feed HID data that is parsed in
user-space back into the kernel.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/Kconfig

@@ -59,6 +59,27 @@ config HIDRAW
 
 	If unsure, say Y.
 
+config UHID
+	tristate "User-space I/O driver support for HID subsystem"
+	depends on HID
+	default n
+	---help---
+	Say Y here if you want to provide HID I/O Drivers from user-space.
+	This allows to write I/O drivers in user-space and feed the data from
+	the device into the kernel. The kernel parses the HID reports, loads the
+	corresponding HID Device Driver or provides input devices on top of your
+	user-space device.
+
+	This driver cannot be used to parse HID-reports in user-space and write
+	special HID-drivers. You should use hidraw for that.
+	Instead, this driver allows to write the transport-layer driver in
+	user-space like USB-HID and Bluetooth-HID do in kernel-space.
+
+	If unsure, say N.
+
+	To compile this driver as a module, choose M here: the
+	module will be called uhid.
+
 source "drivers/hid/usbhid/Kconfig"
 
 menu "Special HID drivers"

drivers/hid/Makefile

@@ -8,6 +8,7 @@ ifdef CONFIG_DEBUG_FS
 endif
 
 obj-$(CONFIG_HID)		+= hid.o
+obj-$(CONFIG_UHID)		+= uhid.o
 
 obj-$(CONFIG_HID_GENERIC)	+= hid-generic.o
 

drivers/hid/uhid.c

@@ -0,0 +1,88 @@
+/*
+ * User-space I/O driver support for HID subsystem
+ * Copyright (c) 2012 David Herrmann
+ */
+
+/*
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ */
+
+#include <linux/atomic.h>
+#include <linux/device.h>
+#include <linux/fs.h>
+#include <linux/hid.h>
+#include <linux/input.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/poll.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/uhid.h>
+#include <linux/wait.h>
+
+#define UHID_NAME	"uhid"
+
+static struct miscdevice uhid_misc;
+
+static int uhid_char_open(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+static int uhid_char_release(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+static ssize_t uhid_char_read(struct file *file, char __user *buffer,
+				size_t count, loff_t *ppos)
+{
+	return 0;
+}
+
+static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
+				size_t count, loff_t *ppos)
+{
+	return 0;
+}
+
+static unsigned int uhid_char_poll(struct file *file, poll_table *wait)
+{
+	return 0;
+}
+
+static const struct file_operations uhid_fops = {
+	.owner		= THIS_MODULE,
+	.open		= uhid_char_open,
+	.release	= uhid_char_release,
+	.read		= uhid_char_read,
+	.write		= uhid_char_write,
+	.poll		= uhid_char_poll,
+	.llseek		= no_llseek,
+};
+
+static struct miscdevice uhid_misc = {
+	.fops		= &uhid_fops,
+	.minor		= MISC_DYNAMIC_MINOR,
+	.name		= UHID_NAME,
+};
+
+static int __init uhid_init(void)
+{
+	return misc_register(&uhid_misc);
+}
+
+static void __exit uhid_exit(void)
+{
+	misc_deregister(&uhid_misc);
+}
+
+module_init(uhid_init);
+module_exit(uhid_exit);
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("David Herrmann <dh.herrmann@gmail.com>");
+MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");