[media] media: Media device node support
The media_devnode structure provides support for registering and unregistering character devices using a dynamic major number. Reference counting is handled internally, making device drivers easier to write without having to solve the open/disconnect race condition issue over and over again. The code is based on video/v4l2-dev.c. [mchehab@redhat.com: Remove linux/smp_lock.h include to not break compilation on bisect] Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Acked-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Laurent Pinchart
Mauro Carvalho Chehab
parent
02adb1cc76
commit
cf4b9211b5
4 changed files with 436 additions and 0 deletions
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@ -13,6 +13,19 @@ if MEDIA_SUPPORT
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comment "Multimedia core support"
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#
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# Media controller
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#
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config MEDIA_CONTROLLER
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bool "Media Controller API (EXPERIMENTAL)"
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depends on EXPERIMENTAL
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---help---
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Enable the media controller API used to query media devices internal
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topology and configure it dynamically.
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This API is mostly used by camera interfaces in embedded platforms.
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#
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# V4L core and enabled API's
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#
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@ -2,6 +2,12 @@
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# Makefile for the kernel multimedia device drivers.
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#
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media-objs := media-devnode.o
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ifeq ($(CONFIG_MEDIA_CONTROLLER),y)
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obj-$(CONFIG_MEDIA_SUPPORT) += media.o
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endif
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obj-y += common/ rc/ video/
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obj-$(CONFIG_VIDEO_DEV) += radio/
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320
drivers/media/media-devnode.c
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320
drivers/media/media-devnode.c
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@ -0,0 +1,320 @@
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/*
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* Media device node
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*
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* Copyright (C) 2010 Nokia Corporation
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*
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* Based on drivers/media/video/v4l2_dev.c code authored by
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* Mauro Carvalho Chehab <mchehab@infradead.org> (version 2)
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* Alan Cox, <alan@lxorguk.ukuu.org.uk> (version 1)
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*
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* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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* Sakari Ailus <sakari.ailus@iki.fi>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* --
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*
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* Generic media device node infrastructure to register and unregister
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* character devices using a dynamic major number and proper reference
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* counting.
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*/
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#include <linux/errno.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/kmod.h>
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#include <linux/slab.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/uaccess.h>
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#include <asm/system.h>
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#include <media/media-devnode.h>
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#define MEDIA_NUM_DEVICES 256
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#define MEDIA_NAME "media"
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static dev_t media_dev_t;
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/*
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* Active devices
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*/
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static DEFINE_MUTEX(media_devnode_lock);
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static DECLARE_BITMAP(media_devnode_nums, MEDIA_NUM_DEVICES);
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/* Called when the last user of the media device exits. */
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static void media_devnode_release(struct device *cd)
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{
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struct media_devnode *mdev = to_media_devnode(cd);
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mutex_lock(&media_devnode_lock);
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/* Delete the cdev on this minor as well */
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cdev_del(&mdev->cdev);
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/* Mark device node number as free */
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clear_bit(mdev->minor, media_devnode_nums);
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mutex_unlock(&media_devnode_lock);
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/* Release media_devnode and perform other cleanups as needed. */
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if (mdev->release)
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mdev->release(mdev);
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}
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static struct bus_type media_bus_type = {
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.name = MEDIA_NAME,
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};
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static ssize_t media_read(struct file *filp, char __user *buf,
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size_t sz, loff_t *off)
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{
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struct media_devnode *mdev = media_devnode_data(filp);
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if (!mdev->fops->read)
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return -EINVAL;
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if (!media_devnode_is_registered(mdev))
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return -EIO;
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return mdev->fops->read(filp, buf, sz, off);
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}
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static ssize_t media_write(struct file *filp, const char __user *buf,
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size_t sz, loff_t *off)
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{
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struct media_devnode *mdev = media_devnode_data(filp);
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if (!mdev->fops->write)
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return -EINVAL;
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if (!media_devnode_is_registered(mdev))
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return -EIO;
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return mdev->fops->write(filp, buf, sz, off);
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}
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static unsigned int media_poll(struct file *filp,
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struct poll_table_struct *poll)
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{
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struct media_devnode *mdev = media_devnode_data(filp);
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if (!media_devnode_is_registered(mdev))
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return POLLERR | POLLHUP;
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if (!mdev->fops->poll)
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return DEFAULT_POLLMASK;
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return mdev->fops->poll(filp, poll);
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}
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static long media_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
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{
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struct media_devnode *mdev = media_devnode_data(filp);
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if (!mdev->fops->ioctl)
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return -ENOTTY;
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if (!media_devnode_is_registered(mdev))
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return -EIO;
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return mdev->fops->ioctl(filp, cmd, arg);
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}
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/* Override for the open function */
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static int media_open(struct inode *inode, struct file *filp)
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{
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struct media_devnode *mdev;
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int ret;
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/* Check if the media device is available. This needs to be done with
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* the media_devnode_lock held to prevent an open/unregister race:
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* without the lock, the device could be unregistered and freed between
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* the media_devnode_is_registered() and get_device() calls, leading to
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* a crash.
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*/
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mutex_lock(&media_devnode_lock);
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mdev = container_of(inode->i_cdev, struct media_devnode, cdev);
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/* return ENXIO if the media device has been removed
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already or if it is not registered anymore. */
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if (!media_devnode_is_registered(mdev)) {
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mutex_unlock(&media_devnode_lock);
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return -ENXIO;
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}
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/* and increase the device refcount */
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get_device(&mdev->dev);
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mutex_unlock(&media_devnode_lock);
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filp->private_data = mdev;
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if (mdev->fops->open) {
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ret = mdev->fops->open(filp);
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if (ret) {
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put_device(&mdev->dev);
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return ret;
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}
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}
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return 0;
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}
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/* Override for the release function */
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static int media_release(struct inode *inode, struct file *filp)
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{
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struct media_devnode *mdev = media_devnode_data(filp);
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int ret = 0;
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if (mdev->fops->release)
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mdev->fops->release(filp);
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/* decrease the refcount unconditionally since the release()
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return value is ignored. */
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put_device(&mdev->dev);
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filp->private_data = NULL;
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return ret;
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}
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static const struct file_operations media_devnode_fops = {
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.owner = THIS_MODULE,
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.read = media_read,
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.write = media_write,
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.open = media_open,
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.unlocked_ioctl = media_ioctl,
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.release = media_release,
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.poll = media_poll,
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.llseek = no_llseek,
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};
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/**
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* media_devnode_register - register a media device node
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* @mdev: media device node structure we want to register
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*
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* The registration code assigns minor numbers and registers the new device node
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* with the kernel. An error is returned if no free minor number can be found,
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* or if the registration of the device node fails.
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*
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* Zero is returned on success.
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*
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* Note that if the media_devnode_register call fails, the release() callback of
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* the media_devnode structure is *not* called, so the caller is responsible for
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* freeing any data.
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*/
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int __must_check media_devnode_register(struct media_devnode *mdev)
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{
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int minor;
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int ret;
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/* Part 1: Find a free minor number */
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mutex_lock(&media_devnode_lock);
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minor = find_next_zero_bit(media_devnode_nums, 0, MEDIA_NUM_DEVICES);
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if (minor == MEDIA_NUM_DEVICES) {
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mutex_unlock(&media_devnode_lock);
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printk(KERN_ERR "could not get a free minor\n");
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return -ENFILE;
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}
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set_bit(mdev->minor, media_devnode_nums);
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mutex_unlock(&media_devnode_lock);
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mdev->minor = minor;
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/* Part 2: Initialize and register the character device */
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cdev_init(&mdev->cdev, &media_devnode_fops);
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mdev->cdev.owner = mdev->fops->owner;
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ret = cdev_add(&mdev->cdev, MKDEV(MAJOR(media_dev_t), mdev->minor), 1);
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if (ret < 0) {
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printk(KERN_ERR "%s: cdev_add failed\n", __func__);
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goto error;
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}
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/* Part 3: Register the media device */
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mdev->dev.bus = &media_bus_type;
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mdev->dev.devt = MKDEV(MAJOR(media_dev_t), mdev->minor);
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mdev->dev.release = media_devnode_release;
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if (mdev->parent)
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mdev->dev.parent = mdev->parent;
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dev_set_name(&mdev->dev, "media%d", mdev->minor);
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ret = device_register(&mdev->dev);
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if (ret < 0) {
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printk(KERN_ERR "%s: device_register failed\n", __func__);
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goto error;
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}
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/* Part 4: Activate this minor. The char device can now be used. */
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set_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
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return 0;
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error:
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cdev_del(&mdev->cdev);
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clear_bit(mdev->minor, media_devnode_nums);
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return ret;
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}
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/**
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* media_devnode_unregister - unregister a media device node
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* @mdev: the device node to unregister
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*
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* This unregisters the passed device. Future open calls will be met with
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* errors.
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*
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* This function can safely be called if the device node has never been
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* registered or has already been unregistered.
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*/
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void media_devnode_unregister(struct media_devnode *mdev)
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{
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/* Check if mdev was ever registered at all */
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if (!media_devnode_is_registered(mdev))
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return;
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mutex_lock(&media_devnode_lock);
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clear_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
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mutex_unlock(&media_devnode_lock);
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device_unregister(&mdev->dev);
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}
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/*
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* Initialise media for linux
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*/
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static int __init media_devnode_init(void)
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{
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int ret;
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printk(KERN_INFO "Linux media interface: v0.10\n");
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ret = alloc_chrdev_region(&media_dev_t, 0, MEDIA_NUM_DEVICES,
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MEDIA_NAME);
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if (ret < 0) {
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printk(KERN_WARNING "media: unable to allocate major\n");
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return ret;
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}
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ret = bus_register(&media_bus_type);
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if (ret < 0) {
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unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
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printk(KERN_WARNING "media: bus_register failed\n");
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return -EIO;
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}
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return 0;
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}
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static void __exit media_devnode_exit(void)
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{
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bus_unregister(&media_bus_type);
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unregister_chrdev_region(media_dev_t, MEDIA_NUM_DEVICES);
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}
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module_init(media_devnode_init)
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module_exit(media_devnode_exit)
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MODULE_AUTHOR("Laurent Pinchart <laurent.pinchart@ideasonboard.com>");
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MODULE_DESCRIPTION("Device node registration for media drivers");
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MODULE_LICENSE("GPL");
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97
include/media/media-devnode.h
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97
include/media/media-devnode.h
Normal file
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@ -0,0 +1,97 @@
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/*
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* Media device node
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*
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* Copyright (C) 2010 Nokia Corporation
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*
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* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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* Sakari Ailus <sakari.ailus@iki.fi>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*
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* --
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*
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* Common functions for media-related drivers to register and unregister media
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* device nodes.
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*/
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#ifndef _MEDIA_DEVNODE_H
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#define _MEDIA_DEVNODE_H
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#include <linux/poll.h>
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#include <linux/fs.h>
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#include <linux/device.h>
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#include <linux/cdev.h>
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/*
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* Flag to mark the media_devnode struct as registered. Drivers must not touch
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* this flag directly, it will be set and cleared by media_devnode_register and
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* media_devnode_unregister.
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*/
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#define MEDIA_FLAG_REGISTERED 0
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struct media_file_operations {
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struct module *owner;
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ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
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ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
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unsigned int (*poll) (struct file *, struct poll_table_struct *);
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long (*ioctl) (struct file *, unsigned int, unsigned long);
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int (*open) (struct file *);
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int (*release) (struct file *);
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};
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/**
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* struct media_devnode - Media device node
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* @parent: parent device
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* @minor: device node minor number
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* @flags: flags, combination of the MEDIA_FLAG_* constants
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*
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* This structure represents a media-related device node.
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*
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* The @parent is a physical device. It must be set by core or device drivers
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* before registering the node.
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*/
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struct media_devnode {
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/* device ops */
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const struct media_file_operations *fops;
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/* sysfs */
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struct device dev; /* media device */
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struct cdev cdev; /* character device */
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struct device *parent; /* device parent */
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/* device info */
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int minor;
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unsigned long flags; /* Use bitops to access flags */
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/* callbacks */
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void (*release)(struct media_devnode *mdev);
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};
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/* dev to media_devnode */
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#define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
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int __must_check media_devnode_register(struct media_devnode *mdev);
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void media_devnode_unregister(struct media_devnode *mdev);
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static inline struct media_devnode *media_devnode_data(struct file *filp)
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{
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return filp->private_data;
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}
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static inline int media_devnode_is_registered(struct media_devnode *mdev)
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{
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return test_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
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}
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#endif /* _MEDIA_DEVNODE_H */
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