This driver allows to write I/O drivers in user-space and feed the input
into the HID subsystem. It operates on the same level as USB-HID and
Bluetooth-HID (HIDP). It does not provide support to write special HID
device drivers but rather provides support for user-space I/O devices to
feed their data into the kernel HID subsystem. The HID subsystem then
loads the HID device drivers for the device and provides input-devices
based on the user-space HID I/O device.
This driver register a new char-device (/dev/uhid). A user-space process
has to open this file for each device that it wants to provide to the
kernel. It can then use write/read to communicate with the UHID driver.
Both input and output data is sent with a uhid_event structure. The "type"
field of the structure specifies what kind of event is sent. There is a
file in Documentation/hid/ explaining the ABI and an example user-space
program that uses this interface in samples/uhid/.
Signed-off-by: David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>
---
Documentation/hid/uhid.txt | 169 +++++++++++++
drivers/hid/Kconfig | 21 ++
drivers/hid/Makefile | 2 +-
drivers/hid/uhid.c | 572 +++++++++++++++++++++++++++++++++++++++++++
include/linux/Kbuild | 1 +
include/linux/uhid.h | 104 ++++++++
samples/uhid/Makefile | 10 +
samples/uhid/uhid-example.c | 381 ++++++++++++++++++++++++++++
8 files changed, 1259 insertions(+), 1 deletion(-)
create mode 100644 Documentation/hid/uhid.txt
create mode 100644 drivers/hid/uhid.c
create mode 100644 include/linux/uhid.h
create mode 100644 samples/uhid/Makefile
create mode 100644 samples/uhid/uhid-example.c
diff --git a/Documentation/hid/uhid.txt b/Documentation/hid/uhid.txt
new file mode 100644
index 0000000..4627c42
--- /dev/null
+++ b/Documentation/hid/uhid.txt
@@ -0,0 +1,169 @@
+ UHID - User-space I/O driver support for HID subsystem
+ ========================================================
+
+The HID subsystem needs two kinds of drivers. In this document we call them:
+
+ 1. The "HID I/O Driver" is the driver that performs raw data I/O to the
+ low-level device. Internally, they register an hid_ll_driver structure with
+ the HID core. They perform device setup, read raw data from the device and
+ push it into the HID subsystem and they provide a callback so the HID
+ subsystem can send data to the device.
+
+ 2. The "HID Device Driver" is the driver that parses HID reports and reacts on
+ them. There are generic drivers like "generic-usb" and "generic-bluetooth"
+ which adhere to the HID specification and provide the standardizes features.
+ But there may be special drivers and quirks for each non-standard device out
+ there. Internally, they use the hid_driver structure.
+
+Historically, the USB stack was the first subsystem to provide an HID I/O
+Driver. However, other standards like Bluetooth have adopted the HID specs and
+may provide HID I/O Drivers, too. The UHID driver allows to implement HID I/O
+Drivers in user-space and feed the data into the kernel HID-subsystem.
+
+This allows user-space to operate on the same level as USB-HID, Bluetooth-HID
+and similar. It does not provide a way to write HID Device Drivers, though. Use
+hidraw for this purpose.
+
+There is an example user-space application in ./samples/uhid/uhid-example.c
+
+The UHID API
+------------
+
+UHID is accessed through a character misc-device. The minor-number is allocated
+dynamically so you need to rely on udev (or similar) to create the device node.
+This is /dev/uhid by default.
+
+If a new device is detected by your HID I/O Driver and you want to register this
+device with the HID subsystem, then you need to open /dev/uhid once for each
+device you want to register. All further communication is done by read()'ing or
+write()'ing "struct uhid_event" objects. Non-blocking operations are supported
+by setting O_NONBLOCK.
+
+struct uhid_event {
+ __u32 type;
+ union {
+ struct uhid_create_req create;
+ struct uhid_data_req data;
+ ...
+ } u;
+};
+
+The "type" field contains the ID of the event. Depending on the ID different
+payloads are sent. You must not split a single event across multiple read()'s or
+multiple write()'s. A single event must always be sent as a whole. Furthermore,
+only a single event can be sent per read() or write(). Pending data is ignored.
+If you want to handle multiple events in a single syscall, then use vectored
+I/O with readv()/writev().
+
+The first thing you should do is sending an UHID_CREATE event. This will
+register the device. UHID will respond with an UHID_START event. You can now
+start sending data to and reading data from UHID. However, unless UHID sends the
+UHID_OPEN event, the internally attached HID Device Driver has no user attached.
+That is, you might put your device asleep unless you receive the UHID_OPEN
+event. If you receive the UHID_OPEN event, you should start I/O. If the last
+user closes the HID device, you will receive an UHID_CLOSE event. This may be
+followed by an UHID_OPEN event again and so on. There is no need to perform
+reference-counting in user-space. That is, you will never receive multiple
+UHID_OPEN events without an UHID_CLOSE event. The HID subsystem performs
+ref-counting for you.
+You may decide to ignore UHID_OPEN/UHID_CLOSE, though. I/O is allowed even
+though the device may have no users.
+
+If you want to send data to the HID subsystem, you send an HID_INPUT event with
+your raw data payload. If the kernel wants to send data to the device, you will
+read an UHID_OUTPUT or UHID_OUTPUT_EV event.
+
+If your device disconnects, you should send an UHID_DESTROY event. This will
+unregister the device. You can now send UHID_CREATE again to register a new
+device.
+If you close() the fd, the device is automatically unregistered and destroyed
+internally.
+
+write()
+-------
+write() allows you to modify the state of the device and feed input data into
+the kernel. The following types are supported: UHID_CREATE, UHID_DESTROY and
+UHID_INPUT. The kernel will parse the event immediately and if the event ID is
+not supported, it will return -EOPNOTSUPP. If the payload is invalid, then
+-EINVAL is returned, otherwise, the amount of data that was read is returned and
+the request was handled successfully.
+
+ UHID_CREATE:
+ This creates the internal HID device. No I/O is possible until you send this
+ event to the kernel. The payload is of type struct uhid_create_req and
+ contains information about your device. You can start I/O now.
+
+ UHID_DESTROY:
+ This destroys the internal HID device. No further I/O will be accepted. There
+ may still be pending messages that you can receive with read() but no further
+ UHID_INPUT events can be sent to the kernel.
+ You can create a new device by sending UHID_CREATE again. There is no need to
+ reopen the character device.
+
+ UHID_INPUT:
+ You must send UHID_CREATE before sending input to the kernel! This event
+ contains a data-payload. This is the raw data that you read from your device.
+ The kernel will parse the HID reports and react on it.
+
+ UHID_FEATURE_ANSWER:
+ If you receive a UHID_FEATURE request you must answer with this request. You
+ must copy the "id" field from the request into the answer. Set the "err" field
+ to 0 if no error occured or to EIO if an I/O error occurred.
+ If "err" is 0 then you should fill the buffer of the answer with the results
+ of the feature request and set "size" correspondingly.
+
+read()
+------
+read() will return a queued ouput report. These output reports can be of type
+UHID_START, UHID_STOP, UHID_OPEN, UHID_CLOSE, UHID_OUTPUT or UHID_OUTPUT_EV. No
+reaction is required to any of them but you should handle them according to your
+needs. Only UHID_OUTPUT and UHID_OUTPUT_EV have payloads.
+
+ UHID_START:
+ This is sent when the HID device is started. Consider this as an answer to
+ UHID_CREATE. This is always the first event that is sent.
+
+ UHID_STOP:
+ This is sent when the HID device is stopped. Consider this as an answer to
+ UHID_DESTROY.
+ If the kernel HID device driver closes the device manually (that is, you
+ didn't send UHID_DESTROY) then you should consider this device closed and send
+ an UHID_DESTROY event. You may want to reregister your device, though. This is
+ always the last message that is sent to you unless you reopen the device with
+ UHID_CREATE.
+
+ UHID_OPEN:
+ This is sent when the HID device is opened. That is, the data that the HID
+ device provides is read by some other process. You may ignore this event but
+ it is useful for power-management. As long as you haven't received this event
+ there is actually no other process that reads your data so there is no need to
+ send UHID_INPUT events to the kernel.
+
+ UHID_CLOSE:
+ This is sent when there are no more processes which read the HID data. It is
+ the counterpart of UHID_OPEN and you may as well ignore this event.
+
+ UHID_OUTPUT:
+ This is sent if the HID device driver wants to send raw data to the I/O
+ device. You should read the payload and forward it to the device. The payload
+ is of type "struct uhid_data_req".
+ This may be received even though you haven't received UHID_OPEN, yet.
+
+ UHID_OUTPUT_EV:
+ Same as UHID_OUTPUT but this contains a "struct input_event" as payload. This
+ is called for force-feedback, LED or similar events which are received through
+ an input device by the HID subsystem. You should convert this into raw reports
+ and send them to your device similar to events of type UHID_OUTPUT.
+
+ UHID_FEATURE:
+ This event is sent if the kernel driver wants to perform a feature request as
+ described in the HID specs. The report-type and report-number are available in
+ the payload.
+ The kernel serializes feature requests so there will never be two in parallel.
+ However, if you fail to respond with a UHID_FEATURE_ANSWER in a time-span of 5
+ seconds, then the requests will be dropped and a new one might be sent.
+ Therefore, the payload also contains an "id" field that identifies every
+ request.
+
+Document by:
+ David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>
diff --git a/drivers/hid/Kconfig b/drivers/hid/Kconfig
index 54cc92f..f6d47cd 100644
--- a/drivers/hid/Kconfig
+++ b/drivers/hid/Kconfig
@@ -55,6 +55,27 @@ 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"
diff --git a/drivers/hid/Makefile b/drivers/hid/Makefile
index 22f1d16..cadb84f 100644
--- a/drivers/hid/Makefile
+++ b/drivers/hid/Makefile
@@ -8,6 +8,7 @@ ifdef CONFIG_DEBUG_FS
endif
obj-$(CONFIG_HID) += hid.o
+obj-$(CONFIG_UHID) += uhid.o
hid-$(CONFIG_HIDRAW) += hidraw.o
@@ -88,4 +89,3 @@ obj-$(CONFIG_HID_WIIMOTE) += hid-wiimote.o
obj-$(CONFIG_USB_HID) += usbhid/
obj-$(CONFIG_USB_MOUSE) += usbhid/
obj-$(CONFIG_USB_KBD) += usbhid/
-
diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
new file mode 100644
index 0000000..df8c0f2
--- /dev/null
+++ b/drivers/hid/uhid.c
@@ -0,0 +1,572 @@
+/*
+ * 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"
+#define UHID_BUFSIZE 32
+
+struct uhid_device {
+ struct mutex devlock;
+ bool running;
+
+ __u8 *rd_data;
+ uint rd_size;
+
+ struct hid_device *hid;
+ struct uhid_event input_buf;
+
+ wait_queue_head_t waitq;
+ spinlock_t qlock;
+ __u8 head;
+ __u8 tail;
+ struct uhid_event *outq[UHID_BUFSIZE];
+
+ struct mutex report_lock;
+ wait_queue_head_t report_wait;
+ atomic_t report_done;
+ atomic_t report_id;
+ struct uhid_event report_buf;
+};
+
+static struct miscdevice uhid_misc;
+
+static void uhid_queue(struct uhid_device *uhid, struct uhid_event *ev)
+{
+ __u8 newhead;
+
+ newhead = (uhid->head + 1) % UHID_BUFSIZE;
+
+ if (newhead != uhid->tail) {
+ uhid->outq[uhid->head] = ev;
+ uhid->head = newhead;
+ wake_up_interruptible(&uhid->waitq);
+ } else {
+ pr_warn("Output queue is full\n");
+ kfree(ev);
+ }
+}
+
+static int uhid_queue_event(struct uhid_device *uhid, unsigned int event)
+{
+ unsigned long flags;
+ struct uhid_event *ev;
+
+ ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+ if (!ev)
+ return -ENOMEM;
+
+ ev->type = event;
+
+ spin_lock_irqsave(&uhid->qlock, flags);
+ uhid_queue(uhid, ev);
+ spin_unlock_irqrestore(&uhid->qlock, flags);
+
+ return 0;
+}
+
+static int uhid_hid_start(struct hid_device *hid)
+{
+ struct uhid_device *uhid = hid->driver_data;
+
+ return uhid_queue_event(uhid, UHID_START);
+}
+
+static void uhid_hid_stop(struct hid_device *hid)
+{
+ struct uhid_device *uhid = hid->driver_data;
+
+ hid->claimed = 0;
+ uhid_queue_event(uhid, UHID_STOP);
+}
+
+static int uhid_hid_open(struct hid_device *hid)
+{
+ struct uhid_device *uhid = hid->driver_data;
+
+ return uhid_queue_event(uhid, UHID_OPEN);
+}
+
+static void uhid_hid_close(struct hid_device *hid)
+{
+ struct uhid_device *uhid = hid->driver_data;
+
+ uhid_queue_event(uhid, UHID_CLOSE);
+}
+
+static int uhid_hid_input(struct input_dev *input, unsigned int type,
+ unsigned int code, int value)
+{
+ struct hid_device *hid = input_get_drvdata(input);
+ struct uhid_device *uhid = hid->driver_data;
+ unsigned long flags;
+ struct uhid_event *ev;
+
+ ev = kzalloc(sizeof(*ev), GFP_ATOMIC);
+ if (!ev)
+ return -ENOMEM;
+
+ ev->type = UHID_OUTPUT_EV;
+ ev->u.output_ev.type = type;
+ ev->u.output_ev.code = code;
+ ev->u.output_ev.value = value;
+
+ spin_lock_irqsave(&uhid->qlock, flags);
+ uhid_queue(uhid, ev);
+ spin_unlock_irqrestore(&uhid->qlock, flags);
+
+ return 0;
+}
+
+static int uhid_hid_parse(struct hid_device *hid)
+{
+ struct uhid_device *uhid = hid->driver_data;
+
+ return hid_parse_report(hid, uhid->rd_data, uhid->rd_size);
+}
+
+static int uhid_hid_get_raw(struct hid_device *hid, unsigned char rnum,
+ __u8 *buf, size_t count, unsigned char rtype)
+{
+ struct uhid_device *uhid = hid->driver_data;
+ __u8 report_type;
+ struct uhid_event *ev;
+ unsigned long flags;
+ int ret;
+ size_t len;
+ struct uhid_feature_answer_req *req;
+
+ if (!uhid->running)
+ return -EIO;
+
+ switch (rtype) {
+ case HID_FEATURE_REPORT:
+ report_type = UHID_FEATURE_REPORT;
+ break;
+ case HID_OUTPUT_REPORT:
+ report_type = UHID_OUTPUT_REPORT;
+ break;
+ case HID_INPUT_REPORT:
+ report_type = UHID_INPUT_REPORT;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ ret = mutex_lock_interruptible(&uhid->report_lock);
+ if (ret)
+ return ret;
+
+ ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+ if (!ev) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+
+ spin_lock_irqsave(&uhid->qlock, flags);
+ ev->type = UHID_FEATURE;
+ ev->u.feature.id = atomic_inc_return(&uhid->report_id);
+ ev->u.feature.rnum = rnum;
+ ev->u.feature.rtype = report_type;
+
+ atomic_set(&uhid->report_done, 0);
+ uhid_queue(uhid, ev);
+ spin_unlock_irqrestore(&uhid->qlock, flags);
+
+ ret = wait_event_interruptible_timeout(uhid->report_wait,
+ atomic_read(&uhid->report_done), 5 * HZ);
+
+ /*
+ * Make sure "uhid->running" is cleared on shutdown before
+ * "uhid->report_done" is set.
+ */
+ smp_rmb();
+ if (!ret || !uhid->running) {
+ ret = -EIO;
+ } else if (ret < 0) {
+ ret = -ERESTARTSYS;
+ } else {
+ spin_lock_irqsave(&uhid->qlock, flags);
+ req = &uhid->report_buf.u.feature_answer;
+
+ if (req->err) {
+ ret = -EIO;
+ } else {
+ ret = 0;
+ len = min(count,
+ min_t(size_t, req->size, UHID_DATA_MAX));
+ memcpy(buf, req->data, len);
+ }
+
+ spin_unlock_irqrestore(&uhid->qlock, flags);
+ }
+
+ atomic_set(&uhid->report_done, 1);
+
+unlock:
+ mutex_unlock(&uhid->report_lock);
+ return ret ? ret : len;
+}
+
+static int uhid_hid_output_raw(struct hid_device *hid, __u8 *buf, size_t count,
+ unsigned char report_type)
+{
+ struct uhid_device *uhid = hid->driver_data;
+ __u8 rtype;
+ unsigned long flags;
+ struct uhid_event *ev;
+
+ switch (report_type) {
+ case HID_FEATURE_REPORT:
+ rtype = UHID_FEATURE_REPORT;
+ break;
+ case HID_OUTPUT_REPORT:
+ rtype = UHID_OUTPUT_REPORT;
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (count < 1 || count > UHID_DATA_MAX)
+ return -EINVAL;
+
+ ev = kzalloc(sizeof(*ev), GFP_KERNEL);
+ if (!ev)
+ return -ENOMEM;
+
+ ev->type = UHID_OUTPUT;
+ ev->u.output.size = count;
+ ev->u.output.rtype = rtype;
+ memcpy(ev->u.output.data, buf, count);
+
+ spin_lock_irqsave(&uhid->qlock, flags);
+ uhid_queue(uhid, ev);
+ spin_unlock_irqrestore(&uhid->qlock, flags);
+
+ return count;
+}
+
+static struct hid_ll_driver uhid_hid_driver = {
+ .start = uhid_hid_start,
+ .stop = uhid_hid_stop,
+ .open = uhid_hid_open,
+ .close = uhid_hid_close,
+ .hidinput_input_event = uhid_hid_input,
+ .parse = uhid_hid_parse,
+};
+
+static int uhid_dev_create(struct uhid_device *uhid,
+ const struct uhid_event *ev)
+{
+ struct hid_device *hid;
+ int ret;
+
+ if (uhid->running)
+ return -EALREADY;
+
+ uhid->rd_size = ev->u.create.rd_size;
+ if (uhid->rd_size <= 0 || uhid->rd_size > HID_MAX_DESCRIPTOR_SIZE)
+ return -EINVAL;
+
+ uhid->rd_data = kmalloc(uhid->rd_size, GFP_KERNEL);
+ if (!uhid->rd_data)
+ return -ENOMEM;
+
+ if (copy_from_user(uhid->rd_data, ev->u.create.rd_data,
+ uhid->rd_size)) {
+ ret = -EFAULT;
+ goto err_free;
+ }
+
+ hid = hid_allocate_device();
+ if (IS_ERR(hid)) {
+ ret = PTR_ERR(hid);
+ goto err_free;
+ }
+
+ strncpy(hid->name, ev->u.create.name, 128);
+ hid->name[127] = 0;
+ strncpy(hid->phys, ev->u.create.phys, 64);
+ hid->phys[63] = 0;
+ strncpy(hid->uniq, ev->u.create.uniq, 64);
+ hid->uniq[63] = 0;
+
+ hid->ll_driver = &uhid_hid_driver;
+ hid->hid_get_raw_report = uhid_hid_get_raw;
+ hid->hid_output_raw_report = uhid_hid_output_raw;
+ hid->bus = ev->u.create.bus;
+ hid->vendor = ev->u.create.vendor;
+ hid->product = ev->u.create.product;
+ hid->version = ev->u.create.version;
+ hid->country = ev->u.create.country;
+ hid->driver_data = uhid;
+ hid->dev.parent = uhid_misc.this_device;
+
+ uhid->hid = hid;
+ uhid->running = true;
+
+ ret = hid_add_device(hid);
+ if (ret) {
+ pr_err("Cannot register HID device\n");
+ goto err_hid;
+ }
+
+ return 0;
+
+err_hid:
+ hid_destroy_device(hid);
+ uhid->hid = NULL;
+ uhid->running = false;
+err_free:
+ kfree(uhid->rd_data);
+ return ret;
+}
+
+static int uhid_dev_destroy(struct uhid_device *uhid)
+{
+ if (!uhid->running)
+ return -EINVAL;
+
+ /* clear "running" before setting "report_done" */
+ uhid->running = false;
+ smp_wmb();
+ atomic_set(&uhid->report_done, 1);
+ wake_up_interruptible(&uhid->report_wait);
+
+ hid_destroy_device(uhid->hid);
+ kfree(uhid->rd_data);
+
+ return 0;
+}
+
+static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
+{
+ if (!uhid->running)
+ return -EINVAL;
+
+ hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
+ min_t(size_t, ev->u.input.size, UHID_DATA_MAX), 0);
+
+ return 0;
+}
+
+static int uhid_dev_feature_answer(struct uhid_device *uhid,
+ struct uhid_event *ev)
+{
+ unsigned long flags;
+
+ if (!uhid->running)
+ return -EINVAL;
+
+ spin_lock_irqsave(&uhid->qlock, flags);
+
+ /* id for old report; drop it silently */
+ if (atomic_read(&uhid->report_id) != ev->u.feature_answer.id)
+ goto unlock;
+ if (atomic_read(&uhid->report_done))
+ goto unlock;
+
+ memcpy(&uhid->report_buf, ev, sizeof(*ev));
+ atomic_set(&uhid->report_done, 1);
+ wake_up_interruptible(&uhid->report_wait);
+
+unlock:
+ spin_unlock_irqrestore(&uhid->qlock, flags);
+ return 0;
+}
+
+static int uhid_char_open(struct inode *inode, struct file *file)
+{
+ struct uhid_device *uhid;
+
+ uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
+ if (!uhid)
+ return -ENOMEM;
+
+ mutex_init(&uhid->devlock);
+ mutex_init(&uhid->report_lock);
+ spin_lock_init(&uhid->qlock);
+ init_waitqueue_head(&uhid->waitq);
+ init_waitqueue_head(&uhid->report_wait);
+ uhid->running = false;
+ atomic_set(&uhid->report_done, 1);
+
+ file->private_data = uhid;
+ nonseekable_open(inode, file);
+
+ return 0;
+}
+
+static int uhid_char_release(struct inode *inode, struct file *file)
+{
+ struct uhid_device *uhid = file->private_data;
+ unsigned int i;
+
+ uhid_dev_destroy(uhid);
+
+ for (i = 0; i < UHID_BUFSIZE; ++i)
+ kfree(uhid->outq[i]);
+
+ kfree(uhid);
+
+ return 0;
+}
+
+static ssize_t uhid_char_read(struct file *file, char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct uhid_device *uhid = file->private_data;
+ int ret;
+ unsigned long flags;
+ size_t len;
+
+ /* they need at least the "type" member of uhid_event */
+ if (count < sizeof(__u32))
+ return -EINVAL;
+
+try_again:
+ if (file->f_flags & O_NONBLOCK) {
+ if (uhid->head == uhid->tail)
+ return -EAGAIN;
+ } else {
+ ret = wait_event_interruptible(uhid->waitq,
+ uhid->head != uhid->tail);
+ if (ret)
+ return ret;
+ }
+
+ ret = mutex_lock_interruptible(&uhid->devlock);
+ if (ret)
+ return ret;
+
+ if (uhid->head == uhid->tail) {
+ mutex_unlock(&uhid->devlock);
+ goto try_again;
+ } else {
+ len = min(count, sizeof(**uhid->outq));
+ if (copy_to_user(buffer, &uhid->outq[uhid->tail], len)) {
+ ret = -EFAULT;
+ } else {
+ kfree(uhid->outq[uhid->tail]);
+ uhid->outq[uhid->tail] = NULL;
+
+ spin_lock_irqsave(&uhid->qlock, flags);
+ uhid->tail = (uhid->tail + 1) % UHID_BUFSIZE;
+ spin_unlock_irqrestore(&uhid->qlock, flags);
+ }
+ }
+
+ mutex_unlock(&uhid->devlock);
+ return ret ? ret : len;
+}
+
+static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
+ size_t count, loff_t *ppos)
+{
+ struct uhid_device *uhid = file->private_data;
+ int ret;
+ size_t len;
+
+ /* we need at least the "type" member of uhid_event */
+ if (count < sizeof(__u32))
+ return -EINVAL;
+
+ ret = mutex_lock_interruptible(&uhid->devlock);
+ if (ret)
+ return ret;
+
+ memset(&uhid->input_buf, 0, sizeof(uhid->input_buf));
+ len = min(count, sizeof(uhid->input_buf));
+ if (copy_from_user(&uhid->input_buf, buffer, len)) {
+ ret = -EFAULT;
+ goto unlock;
+ }
+
+ switch (uhid->input_buf.type) {
+ case UHID_CREATE:
+ ret = uhid_dev_create(uhid, &uhid->input_buf);
+ break;
+ case UHID_DESTROY:
+ ret = uhid_dev_destroy(uhid);
+ break;
+ case UHID_INPUT:
+ ret = uhid_dev_input(uhid, &uhid->input_buf);
+ break;
+ case UHID_FEATURE_ANSWER:
+ ret = uhid_dev_feature_answer(uhid, &uhid->input_buf);
+ break;
+ default:
+ ret = -EOPNOTSUPP;
+ }
+
+unlock:
+ mutex_unlock(&uhid->devlock);
+
+ /* return "count" not "len" to not confuse the caller */
+ return ret ? ret : count;
+}
+
+static unsigned int uhid_char_poll(struct file *file, poll_table *wait)
+{
+ struct uhid_device *uhid = file->private_data;
+
+ poll_wait(file, &uhid->waitq, wait);
+
+ if (uhid->head != uhid->tail)
+ return POLLIN | POLLRDNORM;
+
+ 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@xxxxxxxxx>");
+MODULE_DESCRIPTION("User-space I/O driver support for HID subsystem");
diff --git a/include/linux/Kbuild b/include/linux/Kbuild
index c94e717..b8d5ed0 100644
--- a/include/linux/Kbuild
+++ b/include/linux/Kbuild
@@ -370,6 +370,7 @@ header-y += tty.h
header-y += types.h
header-y += udf_fs_i.h
header-y += udp.h
+header-y += uhid.h
header-y += uinput.h
header-y += uio.h
header-y += ultrasound.h
diff --git a/include/linux/uhid.h b/include/linux/uhid.h
new file mode 100644
index 0000000..9c6974f
--- /dev/null
+++ b/include/linux/uhid.h
@@ -0,0 +1,104 @@
+#ifndef __UHID_H_
+#define __UHID_H_
+
+/*
+ * 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.
+ */
+
+/*
+ * Public header for user-space communication. We try to keep every structure
+ * aligned but to be safe we also use __attribute__((__packed__)). Therefore,
+ * the communication should be ABI compatible even between architectures.
+ */
+
+#include <linux/input.h>
+#include <linux/types.h>
+
+enum uhid_event_type {
+ UHID_CREATE,
+ UHID_DESTROY,
+ UHID_START,
+ UHID_STOP,
+ UHID_OPEN,
+ UHID_CLOSE,
+ UHID_OUTPUT,
+ UHID_OUTPUT_EV,
+ UHID_INPUT,
+ UHID_FEATURE,
+ UHID_FEATURE_ANSWER,
+};
+
+struct uhid_create_req {
+ __u8 name[128];
+ __u8 phys[64];
+ __u8 uniq[64];
+ __u8 __user *rd_data;
+ __u16 rd_size;
+
+ __u16 bus;
+ __u32 vendor;
+ __u32 product;
+ __u32 version;
+ __u32 country;
+} __attribute__((__packed__));
+
+#define UHID_DATA_MAX 4096
+
+enum uhid_report_type {
+ UHID_FEATURE_REPORT,
+ UHID_OUTPUT_REPORT,
+ UHID_INPUT_REPORT,
+};
+
+struct uhid_input_req {
+ __u8 data[UHID_DATA_MAX];
+ __u16 size;
+} __attribute__((__packed__));
+
+struct uhid_output_req {
+ __u8 data[UHID_DATA_MAX];
+ __u16 size;
+ __u8 rtype;
+} __attribute__((__packed__));
+
+struct uhid_output_ev_req {
+ __u16 type;
+ __u16 code;
+ __s32 value;
+} __attribute__((__packed__));
+
+struct uhid_feature_req {
+ __u32 id;
+ __u8 rnum;
+ __u8 rtype;
+} __attribute__((__packed__));
+
+struct uhid_feature_answer_req {
+ __u32 id;
+ __u16 err;
+ __u16 size;
+ __u8 data[UHID_DATA_MAX];
+};
+
+struct uhid_event {
+ __u32 type;
+
+ union {
+ struct uhid_create_req create;
+ struct uhid_input_req input;
+ struct uhid_output_req output;
+ struct uhid_output_ev_req output_ev;
+ struct uhid_feature_req feature;
+ struct uhid_feature_answer_req feature_answer;
+ } u;
+} __attribute__((__packed__));
+
+#endif /* __UHID_H_ */
diff --git a/samples/uhid/Makefile b/samples/uhid/Makefile
new file mode 100644
index 0000000..c95a696
--- /dev/null
+++ b/samples/uhid/Makefile
@@ -0,0 +1,10 @@
+# kbuild trick to avoid linker error. Can be omitted if a module is built.
+obj- := dummy.o
+
+# List of programs to build
+hostprogs-y := uhid-example
+
+# Tell kbuild to always build the programs
+always := $(hostprogs-y)
+
+HOSTCFLAGS_uhid-example.o += -I$(objtree)/usr/include
diff --git a/samples/uhid/uhid-example.c b/samples/uhid/uhid-example.c
new file mode 100644
index 0000000..03ce3c0
--- /dev/null
+++ b/samples/uhid/uhid-example.c
@@ -0,0 +1,381 @@
+/*
+ * UHID Example
+ *
+ * Copyright (c) 2012 David Herrmann <dh.herrmann@xxxxxxxxxxxxxx>
+ *
+ * The code may be used by anyone for any purpose,
+ * and can serve as a starting point for developing
+ * applications using uhid.
+ */
+
+/* UHID Example
+ * This example emulates a basic 3 buttons mouse with wheel over UHID. Run this
+ * program as root and then use the following keys to control the mouse:
+ * q: Quit the application
+ * 1: Toggle left button (down, up, ...)
+ * 2: Toggle right button
+ * 3: Toggle middle button
+ * a: Move mouse left
+ * d: Move mouse right
+ * w: Move mouse up
+ * s: Move mouse down
+ * r: Move wheel up
+ * f: Move wheel down
+ *
+ * If uhid is not available as /dev/uhid, then you can pass a different path as
+ * first argument.
+ * If <linux/uhid.h> is not installed in /usr, then compile this with:
+ * gcc -o ./uhid_test -Wall -I./include ./samples/uhid/uhid-example.c
+ * And ignore the warning about kernel headers. However, it is recommended to
+ * use the installed uhid.h if available.
+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <termios.h>
+#include <unistd.h>
+#include <linux/uhid.h>
+
+/* HID Report Desciptor
+ * We emulate a basic 3 button mouse with wheel. This is the report-descriptor
+ * as the kernel will parse it:
+ *
+ * INPUT[INPUT]
+ * Field(0)
+ * Physical(GenericDesktop.Pointer)
+ * Application(GenericDesktop.Mouse)
+ * Usage(3)
+ * Button.0001
+ * Button.0002
+ * Button.0003
+ * Logical Minimum(0)
+ * Logical Maximum(1)
+ * Report Size(1)
+ * Report Count(3)
+ * Report Offset(0)
+ * Flags( Variable Absolute )
+ * Field(1)
+ * Physical(GenericDesktop.Pointer)
+ * Application(GenericDesktop.Mouse)
+ * Usage(3)
+ * GenericDesktop.X
+ * GenericDesktop.Y
+ * GenericDesktop.Wheel
+ * Logical Minimum(-128)
+ * Logical Maximum(127)
+ * Report Size(8)
+ * Report Count(3)
+ * Report Offset(8)
+ * Flags( Variable Relative )
+ *
+ * This is the mapping that we expect:
+ * Button.0001 ---> Key.LeftBtn
+ * Button.0002 ---> Key.RightBtn
+ * Button.0003 ---> Key.MiddleBtn
+ * GenericDesktop.X ---> Relative.X
+ * GenericDesktop.Y ---> Relative.Y
+ * GenericDesktop.Wheel ---> Relative.Wheel
+ *
+ * This information can be verified by reading /sys/kernel/debug/hid/<dev>/rdesc
+ * This file should print the same information as showed above.
+ */
+
+static unsigned char rdesc[] = {
+ 0x05, 0x01, 0x09, 0x02, 0xa1, 0x01, 0x09, 0x01,
+ 0xa1, 0x00, 0x05, 0x09, 0x19, 0x01, 0x29, 0x03,
+ 0x15, 0x00, 0x25, 0x01, 0x95, 0x03, 0x75, 0x01,
+ 0x81, 0x02, 0x95, 0x01, 0x75, 0x05, 0x81, 0x01,
+ 0x05, 0x01, 0x09, 0x30, 0x09, 0x31, 0x09, 0x38,
+ 0x15, 0x80, 0x25, 0x7f, 0x75, 0x08, 0x95, 0x03,
+ 0x81, 0x06, 0xc0, 0xc0,
+};
+
+static int uhid_write(int fd, const struct uhid_event *ev)
+{
+ ssize_t ret;
+
+ ret = write(fd, ev, sizeof(*ev));
+ if (ret < 0) {
+ fprintf(stderr, "Cannot write to uhid: %m\n");
+ return -errno;
+ } else if (ret != sizeof(*ev)) {
+ fprintf(stderr, "Wrong size written to uhid: %ld != %lu\n",
+ ret, sizeof(ev));
+ return -EFAULT;
+ } else {
+ return 0;
+ }
+}
+
+static int create(int fd)
+{
+ struct uhid_event ev;
+
+ memset(&ev, 0, sizeof(ev));
+ ev.type = UHID_CREATE;
+ strcpy((char*)ev.u.create.name, "test-uhid-device");
+ ev.u.create.rd_data = rdesc;
+ ev.u.create.rd_size = sizeof(rdesc);
+ ev.u.create.bus = BUS_USB;
+ ev.u.create.vendor = 0x15d9;
+ ev.u.create.product = 0x0a37;
+ ev.u.create.version = 0;
+ ev.u.create.country = 0;
+
+ return uhid_write(fd, &ev);
+}
+
+static void destroy(int fd)
+{
+ struct uhid_event ev;
+
+ memset(&ev, 0, sizeof(ev));
+ ev.type = UHID_DESTROY;
+
+ uhid_write(fd, &ev);
+}
+
+static int event(int fd)
+{
+ struct uhid_event ev;
+ ssize_t ret;
+
+ memset(&ev, 0, sizeof(ev));
+ ret = read(fd, &ev, sizeof(ev));
+ if (ret == 0) {
+ fprintf(stderr, "Read HUP on uhid-cdev\n");
+ return -EFAULT;
+ } else if (ret < 0) {
+ fprintf(stderr, "Cannot read uhid-cdev: %m\n");
+ return -errno;
+ } else if (ret != sizeof(ev)) {
+ fprintf(stderr, "Invalid size read from uhid-dev: %ld != %lu\n",
+ ret, sizeof(ev));
+ return -EFAULT;
+ }
+
+ switch (ev.type) {
+ case UHID_START:
+ fprintf(stderr, "UHID_START from uhid-dev\n");
+ break;
+ case UHID_STOP:
+ fprintf(stderr, "UHID_STOP from uhid-dev\n");
+ break;
+ case UHID_OPEN:
+ fprintf(stderr, "UHID_OPEN from uhid-dev\n");
+ break;
+ case UHID_CLOSE:
+ fprintf(stderr, "UHID_CLOSE from uhid-dev\n");
+ break;
+ case UHID_OUTPUT:
+ fprintf(stderr, "UHID_OUTPUT from uhid-dev\n");
+ break;
+ case UHID_OUTPUT_EV:
+ fprintf(stderr, "UHID_OUTPUT_EV from uhid-dev\n");
+ break;
+ default:
+ fprintf(stderr, "Invalid event from uhid-dev: %u\n", ev.type);
+ }
+
+ return 0;
+}
+
+static bool btn1_down;
+static bool btn2_down;
+static bool btn3_down;
+static signed char abs_hor;
+static signed char abs_ver;
+static signed char wheel;
+
+static int send_event(int fd)
+{
+ struct uhid_event ev;
+
+ memset(&ev, 0, sizeof(ev));
+ ev.type = UHID_INPUT;
+ ev.u.input.size = 4;
+
+ if (btn1_down)
+ ev.u.input.data[0] |= 0x1;
+ if (btn2_down)
+ ev.u.input.data[0] |= 0x2;
+ if (btn3_down)
+ ev.u.input.data[0] |= 0x4;
+
+ ev.u.input.data[1] = abs_hor;
+ ev.u.input.data[2] = abs_ver;
+ ev.u.input.data[3] = wheel;
+
+ return uhid_write(fd, &ev);
+}
+
+static int keyboard(int fd)
+{
+ char buf[128];
+ ssize_t ret, i;
+
+ ret = read(STDIN_FILENO, buf, sizeof(buf));
+ if (ret == 0) {
+ fprintf(stderr, "Read HUP on stdin\n");
+ return -EFAULT;
+ } else if (ret < 0) {
+ fprintf(stderr, "Cannot read stdin: %m\n");
+ return -errno;
+ }
+
+ for (i = 0; i < ret; ++i) {
+ switch (buf[i]) {
+ case '1':
+ btn1_down = !btn1_down;
+ ret = send_event(fd);
+ if (ret)
+ return ret;
+ break;
+ case '2':
+ btn2_down = !btn2_down;
+ ret = send_event(fd);
+ if (ret)
+ return ret;
+ break;
+ case '3':
+ btn3_down = !btn3_down;
+ ret = send_event(fd);
+ if (ret)
+ return ret;
+ break;
+ case 'a':
+ abs_hor = -20;
+ ret = send_event(fd);
+ abs_hor = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'd':
+ abs_hor = 20;
+ ret = send_event(fd);
+ abs_hor = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'w':
+ abs_ver = -20;
+ ret = send_event(fd);
+ abs_ver = 0;
+ if (ret)
+ return ret;
+ break;
+ case 's':
+ abs_ver = 20;
+ ret = send_event(fd);
+ abs_ver = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'r':
+ wheel = 1;
+ ret = send_event(fd);
+ wheel = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'f':
+ wheel = -1;
+ ret = send_event(fd);
+ wheel = 0;
+ if (ret)
+ return ret;
+ break;
+ case 'q':
+ return -ECANCELED;
+ default:
+ fprintf(stderr, "Invalid input: %c\n", buf[i]);
+ }
+ }
+
+ return 0;
+}
+
+int main(int argc, char **argv)
+{
+ int fd;
+ const char *path = "/dev/uhid";
+ struct pollfd pfds[2];
+ int ret;
+ struct termios state;
+
+ ret = tcgetattr(STDIN_FILENO, &state);
+ if (ret) {
+ fprintf(stderr, "Cannot get tty state\n");
+ } else {
+ state.c_lflag &= ~ICANON;
+ state.c_cc[VMIN] = 1;
+ ret = tcsetattr(STDIN_FILENO, TCSANOW, &state);
+ if (ret)
+ fprintf(stderr, "Cannot set tty state\n");
+ }
+
+ if (argc >= 2) {
+ if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
+ fprintf(stderr, "Usage: %s [%s]\n", argv[0], path);
+ return EXIT_SUCCESS;
+ } else {
+ path = argv[1];
+ }
+ }
+
+ fprintf(stderr, "Open uhid-cdev %s\n", path);
+ fd = open(path, O_RDWR | O_CLOEXEC);
+ if (fd < 0) {
+ fprintf(stderr, "Cannot open uhid-cdev %s: %m\n", path);
+ return EXIT_FAILURE;
+ }
+
+ fprintf(stderr, "Create uhid device\n");
+ ret = create(fd);
+ if (ret) {
+ close(fd);
+ return EXIT_FAILURE;
+ }
+
+ pfds[0].fd = STDIN_FILENO;
+ pfds[0].events = POLLIN;
+ pfds[1].fd = fd;
+ pfds[1].events = POLLIN;
+
+ fprintf(stderr, "Press 'q' to quit...\n");
+ while (1) {
+ ret = poll(pfds, 2, -1);
+ if (ret < 0) {
+ fprintf(stderr, "Cannot poll for fds: %m\n");
+ break;
+ }
+ if (pfds[0].revents & POLLHUP) {
+ fprintf(stderr, "Received HUP on stdin\n");
+ break;
+ }
+ if (pfds[1].revents & POLLHUP) {
+ fprintf(stderr, "Received HUP on uhid-cdev\n");
+ break;
+ }
+
+ if (pfds[0].revents & POLLIN) {
+ ret = keyboard(fd);
+ if (ret)
+ break;
+ }
+ if (pfds[1].revents & POLLIN) {
+ ret = event(fd);
+ if (ret)
+ break;
+ }
+ }
+
+ fprintf(stderr, "Destroy uhid device\n");
+ destroy(fd);
+ return EXIT_SUCCESS;
+}
--
1.7.10
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