HID: uhid: add internal message buffer

When receiving messages from the HID subsystem, we need to process them
and store them in an internal buffer so user-space can read() on the char
device to retrieve the messages.

This adds a static buffer for 32 messages to each uhid device. Each
message is dynamically allocated so the uhid_device structure does not get
too big.

uhid_queue() adds a message to the buffer. If the buffer is full, the
message is discarded. uhid_queue_event() is an helper for messages without
payload.

This also adds a public header: uhid.h. It contains the declarations for
the user-space API. It is built around "struct uhid_event" which contains
a type field which specifies the event type and each event can then add a
variable-length payload. For now, there is only a dummy event but later
patches will add new event types and payloads.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
This commit is contained in:
David Herrmann 2012-06-10 15:16:14 +02:00 committed by Jiri Kosina
parent 1ccd7a2a33
commit ace3d8614a
3 changed files with 99 additions and 0 deletions

View file

@ -25,16 +25,81 @@
#include <linux/wait.h>
#define UHID_NAME "uhid"
#define UHID_BUFSIZE 32
struct uhid_device {
struct hid_device *hid;
wait_queue_head_t waitq;
spinlock_t qlock;
__u8 head;
__u8 tail;
struct uhid_event *outq[UHID_BUFSIZE];
};
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 {
hid_warn(uhid->hid, "Output queue is full\n");
kfree(ev);
}
}
static int uhid_queue_event(struct uhid_device *uhid, __u32 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_char_open(struct inode *inode, struct file *file)
{
struct uhid_device *uhid;
uhid = kzalloc(sizeof(*uhid), GFP_KERNEL);
if (!uhid)
return -ENOMEM;
spin_lock_init(&uhid->qlock);
init_waitqueue_head(&uhid->waitq);
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;
for (i = 0; i < UHID_BUFSIZE; ++i)
kfree(uhid->outq[i]);
kfree(uhid);
return 0;
}

View file

@ -373,6 +373,7 @@ 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

33
include/linux/uhid.h Normal file
View file

@ -0,0 +1,33 @@
#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_DUMMY,
};
struct uhid_event {
__u32 type;
} __attribute__((__packed__));
#endif /* __UHID_H_ */