/*
* Media device node
*
* Copyright (C) 2010 Nokia Corporation
*
* Based on drivers/media/video/v4l2_dev.c code authored by
* Mauro Carvalho Chehab <mchehab@infradead.org> (version 2)
* Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
*
* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
* Sakari Ailus <sakari.ailus@iki.fi>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* --
*
* Generic media device node infrastructure to register and unregister
* character devices using a dynamic major number and proper reference
* counting.
*/
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/kmod.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include <media/media-devnode.h>
#define MEDIA_NUM_DEVICES 256
#define MEDIA_NAME "media"
static dev_t media_dev_t;
/*
* Active devices
*/
static DEFINE_MUTEX(media_devnode_lock);
static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
/* Called when the last user of the media device exits. */
static void media_devnode_release(struct device *cd)
{
struct media_devnode *mdev = to_media_devnode(cd);
mutex_lock(&media_devnode_lock);
/* Delete the cdev on this minor as well */
cdev_del(&mdev->cdev);
/* Mark device node number as free */
clear_bit(mdev->minor, media_devnode_nums);
mutex_unlock(&media_devnode_lock);
/* Release media_devnode and perform other cleanups as needed. */
if (mdev->release)
mdev->release(mdev);
}
static struct bus_type media_bus_type = {
.name = MEDIA_NAME,
};
static ssize_t media_read(struct file *filp, char __user *buf,
size_t sz, loff_t *off)
{
struct media_devnode *mdev = media_devnode_data(filp);
if (!mdev->fops->read)
return -EINVAL;
if (!media_devnode_is_registered(mdev))
return -EIO;
return mdev->fops->read(filp, buf, sz, off);
}
static ssize_t media_write(struct file *filp, const char __user *buf,
size_t sz, loff_t *off)
{
struct media_devnode *mdev = media_devnode_data(filp);
if (!mdev->fops->write)
return -EINVAL;
if (!media_devnode_is_registered(mdev))
return -EIO;
return mdev->fops->write(filp, buf, sz, off);
}
static unsigned int media_poll(struct file *filp,
struct poll_table_struct *poll)
{
struct media_devnode *mdev = media_devnode_data(filp);
if (!media_devnode_is_registered(mdev))
return POLLERR | POLLHUP;
if (!mdev->fops->poll)
return DEFAULT_POLLMASK;
return mdev->fops->poll(filp, poll);
}
static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct media_devnode *mdev = media_devnode_data(filp);
if (!mdev->fops->ioctl)
return -ENOTTY;
if (!media_devnode_is_registered(mdev))
return -EIO;
return mdev->fops->ioctl(filp, cmd, arg);
}
/* Override for the open function */
static int media_open(struct inode *inode, struct file *filp)
{
struct media_devnode *mdev;
int ret;
/* Check if the media device is available. This needs to be done with
* the media_devnode_lock held to prevent an open/unregister race:
* without the lock, the device could be unregistered and freed between
* the media_devnode_is_registered() and get_device() calls, leading to
* a crash.
*/
mutex_lock(&media_devnode_lock);
mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
/* return ENXIO if the media device has been removed
already or if it is not registered anymore. */
if (!media_devnode_is_registered(mdev)) {
mutex_unlock(&media_devnode_lock);
return -ENXIO;
}
/* and increase the device refcount */
get_device(&mdev->dev);
mutex_unlock(&media_devnode_lock);
filp->private_data = mdev;
if (mdev->fops->open) {
ret = mdev->fops->open(filp);
if (ret) {
put_device(&mdev->dev);
return ret;
}
}
return 0;
}
/* Override for the release function */
static int media_release(struct inode *inode, struct file *filp)
{
struct media_devnode *mdev = media_devnode_data(filp);
int ret = 0;
if (mdev->fops->release)
mdev->fops->release(filp);
/* decrease the refcount unconditionally since the release()
return value is ignored. */
put_device(&mdev->dev);
filp->private_data = NULL;
return ret;
}
static const struct file_operations media_devnode_fops = {
.owner = THIS_MODULE,
.read = media_read,
.write = media_write,
.open = media_open,
.unlocked_ioctl = media_ioctl,
.release = media_release,
.poll = media_poll,
.llseek = no_llseek,
};
/**
* media_devnode_register - register a media device node
* @mdev: media device node structure we want to register
*
* The registration code assigns minor numbers and registers the new device node
* with the kernel. An error is returned if no free minor number can be found,
* or if the registration of the device node fails.
*
* Zero is returned on success.
*
* Note that if the media_devnode_register call fails, the release() callback of
* the media_devnode structure is *not* called, so the caller is responsible for
* freeing any data.
*/
int __must_check media_devnode_register(struct media_devnode *mdev)
{
int minor;
int ret;
/* Part 1: Find a free minor number */
mutex_lock(&media_devnode_lock);
minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0);
if (minor == MEDIA_NUM_DEVICES) {
mutex_unlock(&media_devnode_lock);
printk(KERN_ERR "could not get a free minor\n");
return -ENFILE;
}
set_bit(minor, media_devnode_nums);
mutex_unlock(&media_devnode_lock);
mdev->minor = minor;
/* Part 2: Initialize and register the character device */
cdev_init(&mdev->cdev, &media_devnode_fops);
mdev->cdev.owner = mdev->fops->owner;
ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
if (ret < 0) {
printk(KERN_ERR "%s: cdev_add failed\n", __func__);
goto error;
}
/* Part 3: Register the media device */
mdev->dev.bus = &media_bus_type;
mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
mdev->dev.release = media_devnode_release;
if (mdev->parent)
mdev->dev.parent = mdev->parent;
dev_set_name(&mdev->dev, "media%d", mdev->minor);
ret = device_register(&mdev->dev);
if (ret < 0) {
printk(KERN_ERR "%s: device_register failed\n", __func__);
goto error;
}
/* Part 4: Activate this minor. The char device can now be used. */
set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
return 0;
error:
cdev_del(&mdev->cdev);
clear_bit(mdev->minor, media_devnode_nums);
return ret;
}
/**
* media_devnode_unregister - unregister a media device node
* @mdev: the device node to unregister
*
* This unregisters the passed device. Future open calls will be met with
* errors.
*
* This function can safely be called if the device node has never been
* registered or has already been unregistered.
*/
void media_devnode_unregister(struct media_devnode *mdev)
{
/* Check if mdev was ever registered at all */
if (!media_devnode_is_registered(mdev))
return;
mutex_lock(&media_devnode_lock);
clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
mutex_unlock(&media_devnode_lock);
device_unregister(&mdev->dev);
}
/*
* Initialise media for linux
*/
static int __init media_devnode_init(void)
{
int ret;
printk(KERN_INFO "Linux media interface: v0.10\n");
ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
MEDIA_NAME);
if (ret < 0) {
printk(KERN_WARNING "media: unable to allocate major\n");
return ret;
}
ret = bus_register(&media_bus_type);
if (ret < 0) {
unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
printk(KERN_WARNING "media: bus_register failed\n");
return -EIO;
}
return 0;
}
static void __exit media_devnode_exit(void)
{
bus_unregister(&media_bus_type);
unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
}
subsys_initcall(media_devnode_init);
module_exit(media_devnode_exit)
MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
MODULE_DESCRIPTION("Device node registration for media drivers");
MODULE_LICENSE("GPL");
