Hi Marcel
On Tue, Mar 27, 2012 at 9:13 PM, Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
> Hi David,
>
>> 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.
>
> <snip>
>
>> +#define UHID_NAME "uhid"
>> +#define UHID_BUFSIZE 32
>> +
>> +struct uhid_device {
>> + struct mutex devlock;
>> + bool running;
>> + struct device *parent;
>> +
>> + __u8 *rd_data;
>> + uint rd_size;
>> +
>> + struct hid_device *hid;
>> + struct uhid_event input_buf;
>> +
>> + wait_queue_head_t waitq;
>> + spinlock_t qlock;
>> + struct uhid_event assemble;
>> + __u8 head;
>> + __u8 tail;
>> + struct uhid_event outq[UHID_BUFSIZE];
>> +};
>
> The kernel has a ringbuffer structure. Would it make sense to use that
> one?
>
> Or would using just a SKB queue be better?
I had a look at include/linux/circ_buf.h but it isn't really much of
an help here. It provides 2 macros that could be used but would make
the access to the fields more complicated so I decided to copy it from
uinput. SKB is only for socket-related stuff and has much overhead if
used without sockets. sizeof(struct sk_buff) is about 64KB or more and
is really uncommon outside of ./net/.
>> +static void uhid_queue(struct uhid_device *uhid, const struct uhid_event *ev)
>> +{
>> + __u8 newhead;
>> +
>> + newhead = (uhid->head + 1) % UHID_BUFSIZE;
>> +
>> + if (newhead != uhid->tail) {
>> + memcpy(&uhid->outq[uhid->head], ev, sizeof(struct uhid_event));
>> + uhid->head = newhead;
>> + wake_up_interruptible(&uhid->waitq);
>> + } else {
>> + pr_warn("Output queue is full\n");
>> + }
>> +}
>> +
>> +static int uhid_hid_start(struct hid_device *hid)
>> +{
>> + struct uhid_device *uhid = hid->driver_data;
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&uhid->qlock, flags);
>> + memset(&uhid->assemble, 0, sizeof(uhid->assemble));
>> + uhid->assemble.type = UHID_START;
>> + uhid_queue(uhid, &uhid->assemble);
>> + spin_unlock_irqrestore(&uhid->qlock, flags);
>> +
>> + return 0;
>> +}
>> +
>> +static void uhid_hid_stop(struct hid_device *hid)
>> +{
>> + struct uhid_device *uhid = hid->driver_data;
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&uhid->qlock, flags);
>> + memset(&uhid->assemble, 0, sizeof(uhid->assemble));
>> + uhid->assemble.type = UHID_STOP;
>> + uhid_queue(uhid, &uhid->assemble);
>> + spin_unlock_irqrestore(&uhid->qlock, flags);
>> +
>> + hid->claimed = 0;
>> +}
>> +
>> +static int uhid_hid_open(struct hid_device *hid)
>> +{
>> + struct uhid_device *uhid = hid->driver_data;
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&uhid->qlock, flags);
>> + memset(&uhid->assemble, 0, sizeof(uhid->assemble));
>> + uhid->assemble.type = UHID_OPEN;
>> + uhid_queue(uhid, &uhid->assemble);
>> + spin_unlock_irqrestore(&uhid->qlock, flags);
>> +
>> + return 0;
>> +}
>> +
>> +static void uhid_hid_close(struct hid_device *hid)
>> +{
>> + struct uhid_device *uhid = hid->driver_data;
>> + unsigned long flags;
>> +
>> + spin_lock_irqsave(&uhid->qlock, flags);
>> + memset(&uhid->assemble, 0, sizeof(uhid->assemble));
>> + uhid->assemble.type = UHID_CLOSE;
>> + uhid_queue(uhid, &uhid->assemble);
>> + spin_unlock_irqrestore(&uhid->qlock, flags);
>> +}
>> +
>> +static int uhid_hid_power(struct hid_device *hid, int level)
>> +{
>> + /* TODO: Handle PM-hints. This isn't mandatory so we simply return 0
>> + * here.
>> + */
>> +
>> + return 0;
>> +}
>> +
>> +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;
>> +
>> + spin_lock_irqsave(&uhid->qlock, flags);
>> + memset(&uhid->assemble, 0, sizeof(uhid->assemble));
>> +
>> + uhid->assemble.type = UHID_OUTPUT_EV;
>> + uhid->assemble.u.output_ev.type = type;
>> + uhid->assemble.u.output_ev.code = code;
>> + uhid->assemble.u.output_ev.value = value;
>> +
>> + uhid_queue(uhid, &uhid->assemble);
>> + 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)
>> +{
>> + /* TODO: we currently do not support this request. If we want this we
>> + * would need some kind of stream-locking but it isn't needed by the
>> + * main drivers, anyway.
>> + */
>> +
>> + return -EOPNOTSUPP;
>> +}
>> +
>> +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;
>> +
>> + 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;
>> +
>> + spin_lock_irqsave(&uhid->qlock, flags);
>> + memset(&uhid->assemble, 0, sizeof(uhid->assemble));
>> +
>> + uhid->assemble.type = UHID_OUTPUT;
>> + uhid->assemble.u.output.size = count;
>> + uhid->assemble.u.output.rtype = rtype;
>> + memcpy(uhid->assemble.u.output.data, buf, count);
>> +
>> + uhid_queue(uhid, &uhid->assemble);
>> + 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,
>> + .power = uhid_hid_power,
>> + .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;
>> +
>> + ret = mutex_lock_interruptible(&uhid->devlock);
>> + if (ret)
>> + return ret;
>> +
>> + if (uhid->running) {
>> + ret = -EALREADY;
>> + goto unlock;
>> + }
>> +
>> + uhid->rd_size = ev->u.create.rd_size;
>> + uhid->rd_data = kzalloc(uhid->rd_size, GFP_KERNEL);
>> + if (!uhid->rd_data) {
>> + ret = -ENOMEM;
>> + goto unlock;
>> + }
>> +
>> + 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;
>> + 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->phys[0] = 0;
>> + hid->uniq[0] = 0;
>> + hid->driver_data = uhid;
>> + hid->dev.parent = uhid->parent;
>
> Here we have to make sure that we have all required information provided
> by userspace. Anything else that HID might require to work better. Or
> that BR/EDR or LE provides additionally over USB.
Beside phys and uniq I have copied all information that HIDP and
USBHID use. I haven't found any other field that could be of interest
here. We can also always add UHID_CREATE2 with additional fields to
allow further additions (or use a "size" field as you suggested
below).
>> + uhid->hid = hid;
>> + uhid->running = true;
>> +
>> + ret = hid_add_device(hid);
>> + if (ret) {
>> + pr_err("Cannot register HID device\n");
>> + goto err_hid;
>> + }
>> +
>> + mutex_unlock(&uhid->devlock);
>> +
>> + return 0;
>> +
>> +err_hid:
>> + hid_destroy_device(hid);
>> + uhid->hid = NULL;
>> + uhid->running = false;
>> +err_free:
>> + kfree(uhid->rd_data);
>> +unlock:
>> + mutex_unlock(&uhid->devlock);
>> + return ret;
>> +}
>> +
>> +static int uhid_dev_destroy(struct uhid_device *uhid)
>> +{
>> + int ret;
>> +
>> + ret = mutex_lock_interruptible(&uhid->devlock);
>> + if (ret)
>> + return ret;
>> +
>> + if (!uhid->running) {
>> + ret = -EINVAL;
>> + goto unlock;
>> + }
>> +
>> + hid_destroy_device(uhid->hid);
>> + kfree(uhid->rd_data);
>> + uhid->running = false;
>> +
>> +unlock:
>> + mutex_unlock(&uhid->devlock);
>> + return ret;
>> +}
>> +
>> +static int uhid_dev_input(struct uhid_device *uhid, struct uhid_event *ev)
>> +{
>> + int ret;
>> +
>> + ret = mutex_lock_interruptible(&uhid->devlock);
>> + if (ret)
>> + return ret;
>> +
>> + if (!uhid->running) {
>> + ret = -EINVAL;
>> + goto unlock;
>> + }
>> +
>> + hid_input_report(uhid->hid, HID_INPUT_REPORT, ev->u.input.data,
>> + ev->u.input.size, 0);
>> +
>> +unlock:
>> + mutex_unlock(&uhid->devlock);
>> + return ret;
>> +}
>> +
>> +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);
>> + spin_lock_init(&uhid->qlock);
>> + init_waitqueue_head(&uhid->waitq);
>> + uhid->running = false;
>> + uhid->parent = NULL;
>> +
>> + file->private_data = uhid;
>> + nonseekable_open(inode, file);
>> +
>> + return 0;
>
> return nonseekable_open().
No. See the comment in ./fs/open.c. This function is supposed to never fail
and the only reason it returns int is that it can be used directly in
file_operations.open = nonseekable_open
Also I need to do kfree(uhid) if nonseekable_open() fails so just ignoring
the return value is the recommended way. See evdev.c, joydev.c and other
input devices.
Of course, using it as constant replacement for "return 0;" works, but I
really prefer not confusing the reader of the code ;)
>> +}
>> +
>> +static int uhid_char_release(struct inode *inode, struct file *file)
>> +{
>> + struct uhid_device *uhid = file->private_data;
>> +
>> + uhid_dev_destroy(uhid);
>> + 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 {
>> + 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;
>> +
>> + 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))
>> + return -EFAULT;
>> +
>> + 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;
>> + default:
>> + ret = -EOPNOTSUPP;
>
> switch and case should be on the same indentation.
Ugh, yeah, doesn't make any difference here as the lines are pretty
short but I will fix that. Thanks.
>> + }
>> +
>> + /* 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..67d9c8d
>> --- /dev/null
>> +++ b/include/linux/uhid.h
>> @@ -0,0 +1,84 @@
>> +#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 {
>
> Can we add an UHID_UNSPEC or UHID_INVALID here for the 0 value.
I have no objections here but I didn't need it. Anyway, I can add it.
>> + UHID_CREATE,
>> + UHID_DESTROY,
>> + UHID_START,
>> + UHID_STOP,
>> + UHID_OPEN,
>> + UHID_CLOSE,
>> + UHID_OUTPUT,
>> + UHID_OUTPUT_EV,
>> + UHID_INPUT,
>> +};
>> +
>> +struct uhid_create_req {
>> + __u8 name[128];
>> + __u8 __user *rd_data;
>> + __u16 rd_size;
>> +
>> + __u16 bus;
>> + __u32 vendor;
>> + __u32 product;
>> + __u32 version;
>> + __u32 country;
>> +} __attribute__((packed));
>
> __packed please and all others.
Thanks, I will fix that.
>> +
>> +#define UHID_DATA_MAX 4096
>> +
>> +enum uhid_report_type {
>> + UHID_FEATURE_REPORT,
>> + UHID_OUTPUT_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_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;
>> + } u;
>> +} __attribute__((packed));
>
> What about adding another __u32 len here? Just so we can do some extra
> length checks if needed.
Then "len" field would be an overhead of 4 bytes per packet which is
not needed at all. Of course, it would allow us to extent the
payload-structure without adding new EVENT-types but is it really
needed? Wouldn't it be better to add a single "version" field to
UHID_CREATE and then the size attribute would be fixed for all the
event-payloads?
The "len" field would allow multiple packets per read/write, though.
> Regards
>
> Marcel
Thanks for reviewing. I will resend an updated version in a week.
Regards
David
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