--- /dev/null
+/*
+ * 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.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#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,
+ long (*ioctl_func)(struct file *filp, unsigned int cmd,
+ unsigned long arg))
+{
+ struct media_devnode *mdev = media_devnode_data(filp);
+
+ if (!ioctl_func)
+ return -ENOTTY;
+
+ if (!media_devnode_is_registered(mdev))
+ return -EIO;
+
+ return ioctl_func(filp, cmd, arg);
+}
+
+static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+ struct media_devnode *mdev = media_devnode_data(filp);
+
+ return __media_ioctl(filp, cmd, arg, mdev->fops->ioctl);
+}
+
+#ifdef CONFIG_COMPAT
+
+static long media_compat_ioctl(struct file *filp, unsigned int cmd,
+ unsigned long arg)
+{
+ struct media_devnode *mdev = media_devnode_data(filp);
+
+ return __media_ioctl(filp, cmd, arg, mdev->fops->compat_ioctl);
+}
+
+#endif /* CONFIG_COMPAT */
+
+/* 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);
+
+ 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 0;
+}
+
+static const struct file_operations media_devnode_fops = {
+ .owner = THIS_MODULE,
+ .read = media_read,
+ .write = media_write,
+ .open = media_open,
+ .unlocked_ioctl = media_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = media_compat_ioctl,
+#endif /* CONFIG_COMPAT */
+ .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,
+ struct module *owner)
+{
+ 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);
+ pr_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 = owner;
+
+ ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
+ if (ret < 0) {
+ pr_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) {
+ pr_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;
+
+ pr_info("Linux media interface: v0.10\n");
+ ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
+ MEDIA_NAME);
+ if (ret < 0) {
+ pr_warn("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);
+ pr_warn("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");
Code Review / kvmfornfv.git / blobdiff