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drivers/media/media-devnode.c
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/* * 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. */ |
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#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> |
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#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); |
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minor = find_next_zero_bit(media_devnode_nums, MEDIA_NUM_DEVICES, 0); |
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if (minor == MEDIA_NUM_DEVICES) { mutex_unlock(&media_devnode_lock); |
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pr_err("could not get a free minor "); |
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return -ENFILE; } |
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set_bit(minor, media_devnode_nums); |
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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) { |
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pr_err("%s: cdev_add failed ", __func__); |
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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) { |
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pr_err("%s: device_register failed ", __func__); |
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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; |
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pr_info("Linux media interface: v0.10 "); |
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ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES, MEDIA_NAME); if (ret < 0) { |
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pr_warn("unable to allocate major "); |
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return ret; } ret = bus_register(&media_bus_type); if (ret < 0) { unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES); |
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pr_warn("bus_register failed "); |
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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); } |
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subsys_initcall(media_devnode_init); |
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module_exit(media_devnode_exit) MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>"); MODULE_DESCRIPTION("Device node registration for media drivers"); MODULE_LICENSE("GPL"); |