diff options
Diffstat (limited to 'drivers/media/mc/mc-dev-allocator.c')
-rw-r--r-- | drivers/media/mc/mc-dev-allocator.c | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/drivers/media/mc/mc-dev-allocator.c b/drivers/media/mc/mc-dev-allocator.c new file mode 100644 index 000000000000..ae17887dec59 --- /dev/null +++ b/drivers/media/mc/mc-dev-allocator.c @@ -0,0 +1,135 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * media-dev-allocator.c - Media Controller Device Allocator API + * + * Copyright (c) 2019 Shuah Khan <shuah@kernel.org> + * + * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com> + */ + +/* + * This file adds a global refcounted Media Controller Device Instance API. + * A system wide global media device list is managed and each media device + * includes a kref count. The last put on the media device releases the media + * device instance. + * + */ + +#include <linux/kref.h> +#include <linux/module.h> +#include <linux/slab.h> +#include <linux/usb.h> + +#include <media/media-device.h> +#include <media/media-dev-allocator.h> + +static LIST_HEAD(media_device_list); +static DEFINE_MUTEX(media_device_lock); + +struct media_device_instance { + struct media_device mdev; + struct module *owner; + struct list_head list; + struct kref refcount; +}; + +static inline struct media_device_instance * +to_media_device_instance(struct media_device *mdev) +{ + return container_of(mdev, struct media_device_instance, mdev); +} + +static void media_device_instance_release(struct kref *kref) +{ + struct media_device_instance *mdi = + container_of(kref, struct media_device_instance, refcount); + + dev_dbg(mdi->mdev.dev, "%s: releasing Media Device\n", __func__); + + mutex_lock(&media_device_lock); + + media_device_unregister(&mdi->mdev); + media_device_cleanup(&mdi->mdev); + + list_del(&mdi->list); + mutex_unlock(&media_device_lock); + + kfree(mdi); +} + +/* Callers should hold media_device_lock when calling this function */ +static struct media_device *__media_device_get(struct device *dev, + const char *module_name, + struct module *owner) +{ + struct media_device_instance *mdi; + + list_for_each_entry(mdi, &media_device_list, list) { + if (mdi->mdev.dev != dev) + continue; + + kref_get(&mdi->refcount); + + /* get module reference for the media_device owner */ + if (owner != mdi->owner && !try_module_get(mdi->owner)) + dev_err(dev, + "%s: module %s get owner reference error\n", + __func__, module_name); + else + dev_dbg(dev, "%s: module %s got owner reference\n", + __func__, module_name); + return &mdi->mdev; + } + + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); + if (!mdi) + return NULL; + + mdi->owner = owner; + kref_init(&mdi->refcount); + list_add_tail(&mdi->list, &media_device_list); + + dev_dbg(dev, "%s: Allocated media device for owner %s\n", + __func__, module_name); + return &mdi->mdev; +} + +struct media_device *media_device_usb_allocate(struct usb_device *udev, + const char *module_name, + struct module *owner) +{ + struct media_device *mdev; + + mutex_lock(&media_device_lock); + mdev = __media_device_get(&udev->dev, module_name, owner); + if (!mdev) { + mutex_unlock(&media_device_lock); + return ERR_PTR(-ENOMEM); + } + + /* check if media device is already initialized */ + if (!mdev->dev) + __media_device_usb_init(mdev, udev, udev->product, + module_name); + mutex_unlock(&media_device_lock); + return mdev; +} +EXPORT_SYMBOL_GPL(media_device_usb_allocate); + +void media_device_delete(struct media_device *mdev, const char *module_name, + struct module *owner) +{ + struct media_device_instance *mdi = to_media_device_instance(mdev); + + mutex_lock(&media_device_lock); + /* put module reference for the media_device owner */ + if (mdi->owner != owner) { + module_put(mdi->owner); + dev_dbg(mdi->mdev.dev, + "%s: module %s put owner module reference\n", + __func__, module_name); + } + mutex_unlock(&media_device_lock); + kref_put(&mdi->refcount, media_device_instance_release); +} +EXPORT_SYMBOL_GPL(media_device_delete); |