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    Subject[PATCH v9 01/12] media: Media device node support
    Date
    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.

    Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
    ---
    drivers/media/Kconfig | 13 ++
    drivers/media/Makefile | 6 +
    drivers/media/media-devnode.c | 321 +++++++++++++++++++++++++++++++++++++++++
    include/media/media-devnode.h | 97 +++++++++++++
    4 files changed, 437 insertions(+), 0 deletions(-)
    create mode 100644 drivers/media/media-devnode.c
    create mode 100644 include/media/media-devnode.h

    diff --git a/drivers/media/Kconfig b/drivers/media/Kconfig
    index 81b3ba8..2466f2b 100644
    --- a/drivers/media/Kconfig
    +++ b/drivers/media/Kconfig
    @@ -14,6 +14,19 @@ if MEDIA_SUPPORT
    comment "Multimedia core support"

    #
    +# Media controller
    +#
    +
    +config MEDIA_CONTROLLER
    + bool "Media Controller API (EXPERIMENTAL)"
    + depends on EXPERIMENTAL
    + ---help---
    + Enable the media controller API used to query media devices internal
    + topology and configure it dynamically.
    +
    + This API is mostly used by camera interfaces in embedded platforms.
    +
    +#
    # V4L core and enabled API's
    #

    diff --git a/drivers/media/Makefile b/drivers/media/Makefile
    index b603ea6..d56349f 100644
    --- a/drivers/media/Makefile
    +++ b/drivers/media/Makefile
    @@ -2,6 +2,12 @@
    # Makefile for the kernel multimedia device drivers.
    #

    +media-objs := media-devnode.o
    +
    +ifeq ($(CONFIG_MEDIA_CONTROLLER),y)
    + obj-$(CONFIG_MEDIA_SUPPORT) += media.o
    +endif
    +
    obj-y += common/ rc/ video/

    obj-$(CONFIG_VIDEO_DEV) += radio/
    diff --git a/drivers/media/media-devnode.c b/drivers/media/media-devnode.c
    new file mode 100644
    index 0000000..5509984
    --- /dev/null
    +++ b/drivers/media/media-devnode.c
    @@ -0,0 +1,321 @@
    +/*
    + * 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/smp_lock.h>
    +#include <linux/string.h>
    +#include <linux/types.h>
    +#include <linux/uaccess.h>
    +#include <asm/system.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, 0, MEDIA_NUM_DEVICES);
    + if (minor == MEDIA_NUM_DEVICES) {
    + mutex_unlock(&media_devnode_lock);
    + printk(KERN_ERR "could not get a free minor\n");
    + return -ENFILE;
    + }
    +
    + set_bit(mdev->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);
    +}
    +
    +module_init(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");
    diff --git a/include/media/media-devnode.h b/include/media/media-devnode.h
    new file mode 100644
    index 0000000..f6caafc
    --- /dev/null
    +++ b/include/media/media-devnode.h
    @@ -0,0 +1,97 @@
    +/*
    + * Media device node
    + *
    + * Copyright (C) 2010 Nokia Corporation
    + *
    + * 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
    + *
    + * --
    + *
    + * Common functions for media-related drivers to register and unregister media
    + * device nodes.
    + */
    +
    +#ifndef _MEDIA_DEVNODE_H
    +#define _MEDIA_DEVNODE_H
    +
    +#include <linux/poll.h>
    +#include <linux/fs.h>
    +#include <linux/device.h>
    +#include <linux/cdev.h>
    +
    +/*
    + * Flag to mark the media_devnode struct as registered. Drivers must not touch
    + * this flag directly, it will be set and cleared by media_devnode_register and
    + * media_devnode_unregister.
    + */
    +#define MEDIA_FLAG_REGISTERED 0
    +
    +struct media_file_operations {
    + struct module *owner;
    + ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
    + ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
    + unsigned int (*poll) (struct file *, struct poll_table_struct *);
    + long (*ioctl) (struct file *, unsigned int, unsigned long);
    + int (*open) (struct file *);
    + int (*release) (struct file *);
    +};
    +
    +/**
    + * struct media_devnode - Media device node
    + * @parent: parent device
    + * @minor: device node minor number
    + * @flags: flags, combination of the MEDIA_FLAG_* constants
    + *
    + * This structure represents a media-related device node.
    + *
    + * The @parent is a physical device. It must be set by core or device drivers
    + * before registering the node.
    + */
    +struct media_devnode {
    + /* device ops */
    + const struct media_file_operations *fops;
    +
    + /* sysfs */
    + struct device dev; /* media device */
    + struct cdev cdev; /* character device */
    + struct device *parent; /* device parent */
    +
    + /* device info */
    + int minor;
    + unsigned long flags; /* Use bitops to access flags */
    +
    + /* callbacks */
    + void (*release)(struct media_devnode *mdev);
    +};
    +
    +/* dev to media_devnode */
    +#define to_media_devnode(cd) container_of(cd, struct media_devnode, dev)
    +
    +int __must_check media_devnode_register(struct media_devnode *mdev);
    +void media_devnode_unregister(struct media_devnode *mdev);
    +
    +static inline struct media_devnode *media_devnode_data(struct file *filp)
    +{
    + return filp->private_data;
    +}
    +
    +static inline int media_devnode_is_registered(struct media_devnode *mdev)
    +{
    + return test_bit(MEDIA_FLAG_REGISTERED, &mdev->flags);
    +}
    +
    +#endif /* _MEDIA_DEVNODE_H */
    --
    1.7.3.4


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