| Message ID | efdba25cd9ad3b5fa025ed91613921641058a727.1463158822.git.shuahkh@osg.samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Hi Shuah, Some comments below: On 05/13/2016 07:09 PM, Shuah Khan wrote: > Media Device Allocator API to allows multiple drivers share a media device. > Using this API, drivers can allocate a media device with the shared struct > device as the key. Once the media device is allocated by a driver, other > drivers can get a reference to it. The media device is released when all > the references are released. > > Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> > --- > drivers/media/Makefile | 3 +- > drivers/media/media-dev-allocator.c | 139 ++++++++++++++++++++++++++++++++++++ > include/media/media-dev-allocator.h | 118 ++++++++++++++++++++++++++++++ > 3 files changed, 259 insertions(+), 1 deletion(-) > create mode 100644 drivers/media/media-dev-allocator.c > create mode 100644 include/media/media-dev-allocator.h > > diff --git a/drivers/media/Makefile b/drivers/media/Makefile > index e608bbc..b08f091 100644 > --- a/drivers/media/Makefile > +++ b/drivers/media/Makefile > @@ -2,7 +2,8 @@ > # Makefile for the kernel multimedia device drivers. > # > > -media-objs := media-device.o media-devnode.o media-entity.o > +media-objs := media-device.o media-devnode.o media-entity.o \ > + media-dev-allocator.o > > # > # I2C drivers should come before other drivers, otherwise they'll fail > diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c > new file mode 100644 > index 0000000..b49ab55 > --- /dev/null > +++ b/drivers/media/media-dev-allocator.c > @@ -0,0 +1,139 @@ > +/* > + * media-dev-allocator.c - Media Controller Device Allocator API > + * > + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com> > + * Copyright (c) 2016 Samsung Electronics Co., Ltd. > + * > + * This file is released under the GPLv2. > + * 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/slab.h> > +#include <linux/kref.h> > +#include <linux/usb.h> > +#include <media/media-device.h> > + > +static LIST_HEAD(media_device_list); > +static DEFINE_MUTEX(media_device_lock); > + > +struct media_device_instance { > + struct media_device mdev; > + struct list_head list; > + struct device *dev; > + 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: mdev=%p\n", __func__, &mdi->mdev); > + > + 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); > +} > + > +static struct media_device *__media_device_get(struct device *dev, > + bool allocate) > +{ > + struct media_device_instance *mdi; > + > + mutex_lock(&media_device_lock); > + > + list_for_each_entry(mdi, &media_device_list, list) { > + if (mdi->dev == dev) { > + kref_get(&mdi->refcount); > + dev_dbg(dev, "%s: get mdev=%p\n", > + __func__, &mdi->mdev); > + goto done; > + } > + } > + > + if (!allocate) { > + mdi = NULL; > + goto done; > + } > + > + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); > + if (!mdi) > + goto done; > + > + mdi->dev = dev; > + kref_init(&mdi->refcount); > + list_add_tail(&mdi->list, &media_device_list); > + > + dev_dbg(dev, "%s: alloc mdev=%p\n", __func__, &mdi->mdev); > + > +done: > + mutex_unlock(&media_device_lock); > + > + return mdi ? &mdi->mdev : NULL; > +} > + > +struct media_device *media_device_allocate(struct device *dev) > +{ > + dev_dbg(dev, "%s\n", __func__); > + return __media_device_get(dev, true); > +} > +EXPORT_SYMBOL_GPL(media_device_allocate); Do we need this function? Whenever a media device is allocated, you also need to initialize the media device with the media_device_lock held (as happens below in media_device_usb_allocate). You can't really use this function standalone as far as I can see. An alternative might be to pass a callback function with media_device_allocate that initialized the media device. That would ensure that there are no race conditions since media_device_allocate can lock media_device_lock before calling the callback. > + > +struct media_device *media_device_usb_allocate(struct usb_device *udev, > + char *driver_name) > +{ > + struct media_device *mdev; > + > + mdev = media_device_allocate(&udev->dev); > + if (!mdev) > + return ERR_PTR(-ENOMEM); > + > + /* check if media device is already initialized */ > + mutex_lock(&media_device_lock); > + if (!mdev->dev) > + __media_device_usb_init(mdev, udev, udev->product, > + driver_name); > + mutex_unlock(&media_device_lock); > + > + return mdev; > +} > +EXPORT_SYMBOL_GPL(media_device_usb_allocate); > + > +/* don't allocate - get reference if one is found */ > +struct media_device *media_device_get(struct media_device *mdev) > +{ > + struct media_device_instance *mdi = to_media_device_instance(mdev); > + > + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); > + return __media_device_get(mdi->dev, false); > +} > +EXPORT_SYMBOL_GPL(media_device_get); Do we need this anywhere? It makes no sense to call this standalone, at least, not that I can see. You just have different drivers that all call media_device_usb_allocate, and they also call media_device_put when they are done with it. See also my comments for the next patch. > + > +void media_device_put(struct media_device *mdev) > +{ > + struct media_device_instance *mdi = to_media_device_instance(mdev); > + > + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); > + kref_put(&mdi->refcount, media_device_instance_release); > +} > +EXPORT_SYMBOL_GPL(media_device_put); > diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h > new file mode 100644 > index 0000000..a63dfc6 > --- /dev/null > +++ b/include/media/media-dev-allocator.h > @@ -0,0 +1,118 @@ > +/* > + * media-dev-allocator.h - Media Controller Device Allocator API > + * > + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com> > + * Copyright (c) 2016 Samsung Electronics Co., Ltd. > + * > + * This file is released under the GPLv2. > + * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com> > + */ > + > +/* > + * This file adds a global ref-counted 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. > +*/ > + > +#ifndef _MEDIA_DEV_ALLOCTOR_H > +#define _MEDIA_DEV_ALLOCTOR_H > + > +struct usb_device; > + > +#ifdef CONFIG_MEDIA_CONTROLLER > +/** > + * DOC: Media Controller Device Allocator API > + * > + * When media device belongs to more than one driver, the shared media device > + * is allocated with the shared struct device as the key for look ups. > + * > + * Shared media device should stay in registered state until the last driver > + * unregisters it. In addition, media device should be released when all the > + * references are released. Each driver gets a reference to the media device > + * during probe, when it allocates the media device. If media device is already > + * allocated, allocate API bumps up the refcount and return the existing media > + * device. Driver puts the reference back from its disconnect routine when it > + * calls media_device_unregister_put(). > + * > + * Media device is unregistered and cleaned up from the kref put handler to > + * ensure that the media device stays in registered state until the last driver > + * unregisters the media device. > + * > + * Media Device can be in any the following states: > + * > + * - Allocated I don't think this is a real state. It's either unregistered or allocated and registered. Just 'allocated' doesn't really make sense. This ties in to my comment about media_device_allocate(). > + * - Registered (could be tied to more than one driver) > + * - Unregistered and released in the kref put handler. I would probably drop these 5 lines altogether. > + * > + * Driver Usage: > + * > + * Drivers should use the media-core routines to get register reference and > + * use the media_device_unregister_put() routine to make sure the shared > + * media device delete is handled correctly. > + * > + * driver probe: > + * Call media_device_usb_allocate() to allocate or get a reference > + * Call media_device_register(), if media devnode isn't registered > + * > + * driver disconnect: > + * Call media_device_unregister_put() to put the reference. There is no media_device_unregister_put() (yet). That should be in the next patch. > + * > + */ > + > +/** > + * media_device_usb_allocate() - Allocate and return media device > + * > + * @udev - struct usb_device pointer > + * @driver_name > + * > + * This interface should be called to allocate a media device when multiple > + * drivers share usb_device and the media device. This interface allocates > + * media device and calls media_device_usb_init() to initialize it. > + * > + */ > +struct media_device *media_device_usb_allocate(struct usb_device *udev, > + char *driver_name); > +/** > + * media_device_allocate() - Allocate and return global media device > + * > + * @dev - struct device pointer > + * > + * This interface should be called to allocate media device. A new media > + * device instance is created and added to the system wide media device > + * instance list. If media device instance exists, media_device_allocate() > + * increments the reference count and returns the media device. When more > + * than one driver control the media device, the first driver to probe will > + * allocate and the second driver when it calls media_device_allocate(), > + * it will get a reference. > + * > + */ > +struct media_device *media_device_allocate(struct device *dev); > +/** > + * media_device_get() - Get reference to a registered media device. > + * > + * @mdev - struct media_device pointer > + * > + * This interface should be called to get a reference to an allocated media > + * device. > + */ > +struct media_device *media_device_get(struct media_device *mdev); > +/** > + * media_device_put() - Release media device. Calls kref_put(). > + * > + * @mdev - struct media_device pointer > + * > + * This interface should be called to put Media Device Instance kref. > + */ > +void media_device_put(struct media_device *mdev); > +#else > +static inline struct media_device *media_device_usb_allocate( > + struct usb_device *udev, char *driver_name) > + { return NULL; } > +static inline struct media_device *media_device_allocate(struct device *dev) > + { return NULL; } > +static inline struct media_device *media_device_get(struct media_device *mdev) > + { return NULL; } > +static inline void media_device_put(struct media_device *mdev) { } > +#endif /* CONFIG_MEDIA_CONTROLLER */ > +#endif > Regards, Hans -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 05/23/2016 05:26 AM, Hans Verkuil wrote: > Hi Shuah, > > Some comments below: Thanks for the review. > > On 05/13/2016 07:09 PM, Shuah Khan wrote: >> Media Device Allocator API to allows multiple drivers share a media device. >> Using this API, drivers can allocate a media device with the shared struct >> device as the key. Once the media device is allocated by a driver, other >> drivers can get a reference to it. The media device is released when all >> the references are released. >> >> Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> >> --- >> drivers/media/Makefile | 3 +- >> drivers/media/media-dev-allocator.c | 139 ++++++++++++++++++++++++++++++++++++ >> include/media/media-dev-allocator.h | 118 ++++++++++++++++++++++++++++++ >> 3 files changed, 259 insertions(+), 1 deletion(-) >> create mode 100644 drivers/media/media-dev-allocator.c >> create mode 100644 include/media/media-dev-allocator.h >> >> diff --git a/drivers/media/Makefile b/drivers/media/Makefile >> index e608bbc..b08f091 100644 >> --- a/drivers/media/Makefile >> +++ b/drivers/media/Makefile >> @@ -2,7 +2,8 @@ >> # Makefile for the kernel multimedia device drivers. >> # >> >> -media-objs := media-device.o media-devnode.o media-entity.o >> +media-objs := media-device.o media-devnode.o media-entity.o \ >> + media-dev-allocator.o >> >> # >> # I2C drivers should come before other drivers, otherwise they'll fail >> diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c >> new file mode 100644 >> index 0000000..b49ab55 >> --- /dev/null >> +++ b/drivers/media/media-dev-allocator.c >> @@ -0,0 +1,139 @@ >> +/* >> + * media-dev-allocator.c - Media Controller Device Allocator API >> + * >> + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com> >> + * Copyright (c) 2016 Samsung Electronics Co., Ltd. >> + * >> + * This file is released under the GPLv2. >> + * 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/slab.h> >> +#include <linux/kref.h> >> +#include <linux/usb.h> >> +#include <media/media-device.h> >> + >> +static LIST_HEAD(media_device_list); >> +static DEFINE_MUTEX(media_device_lock); >> + >> +struct media_device_instance { >> + struct media_device mdev; >> + struct list_head list; >> + struct device *dev; >> + 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: mdev=%p\n", __func__, &mdi->mdev); >> + >> + 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); >> +} >> + >> +static struct media_device *__media_device_get(struct device *dev, >> + bool allocate) >> +{ >> + struct media_device_instance *mdi; >> + >> + mutex_lock(&media_device_lock); >> + >> + list_for_each_entry(mdi, &media_device_list, list) { >> + if (mdi->dev == dev) { >> + kref_get(&mdi->refcount); >> + dev_dbg(dev, "%s: get mdev=%p\n", >> + __func__, &mdi->mdev); >> + goto done; >> + } >> + } >> + >> + if (!allocate) { >> + mdi = NULL; >> + goto done; >> + } >> + >> + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); >> + if (!mdi) >> + goto done; >> + >> + mdi->dev = dev; >> + kref_init(&mdi->refcount); >> + list_add_tail(&mdi->list, &media_device_list); >> + >> + dev_dbg(dev, "%s: alloc mdev=%p\n", __func__, &mdi->mdev); >> + >> +done: >> + mutex_unlock(&media_device_lock); >> + >> + return mdi ? &mdi->mdev : NULL; >> +} >> + >> +struct media_device *media_device_allocate(struct device *dev) >> +{ >> + dev_dbg(dev, "%s\n", __func__); >> + return __media_device_get(dev, true); >> +} >> +EXPORT_SYMBOL_GPL(media_device_allocate); > > Do we need this function? Whenever a media device is allocated, you also need > to initialize the media device with the media_device_lock held (as happens > below in media_device_usb_allocate). You can't really use this function > standalone as far as I can see. > > An alternative might be to pass a callback function with media_device_allocate > that initialized the media device. That would ensure that there are no race > conditions since media_device_allocate can lock media_device_lock before > calling the callback. You are right, it is not used and all the usb drivers will use the media_device_usb_allocate() and for pci drivers that have the need to share the media device, we could add media_device_pci_allocate(). I think deleting this and collapsing the logic media_device_usb_allocate() will help with the locking as well. I will fix this. I can delete this routine all together and make some changes to __media_device_get() to expect to be called media_device_lock held. That should work well. > >> + >> +struct media_device *media_device_usb_allocate(struct usb_device *udev, >> + char *driver_name) >> +{ >> + struct media_device *mdev; >> + >> + mdev = media_device_allocate(&udev->dev); >> + if (!mdev) >> + return ERR_PTR(-ENOMEM); >> + >> + /* check if media device is already initialized */ >> + mutex_lock(&media_device_lock); >> + if (!mdev->dev) >> + __media_device_usb_init(mdev, udev, udev->product, >> + driver_name); >> + mutex_unlock(&media_device_lock); >> + >> + return mdev; >> +} >> +EXPORT_SYMBOL_GPL(media_device_usb_allocate); >> + >> +/* don't allocate - get reference if one is found */ >> +struct media_device *media_device_get(struct media_device *mdev) >> +{ >> + struct media_device_instance *mdi = to_media_device_instance(mdev); >> + >> + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); >> + return __media_device_get(mdi->dev, false); >> +} >> +EXPORT_SYMBOL_GPL(media_device_get); > > Do we need this anywhere? It makes no sense to call this standalone, at least, not > that I can see. You just have different drivers that all call media_device_usb_allocate, > and they also call media_device_put when they are done with it. See also my comments > for the next patch. You are right. It was needed when I originally did this patch series and used this to fix the lifetime issue. media_device_get() used to get called from media_device_open() and media_device_put() from media_device_close(). I left it in there just in case, there is a need to get a reference, but I think it can be added later when the need arises. I will delete this. >> + >> +void media_device_put(struct media_device *mdev) >> +{ >> + struct media_device_instance *mdi = to_media_device_instance(mdev); >> + >> + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); >> + kref_put(&mdi->refcount, media_device_instance_release); >> +} >> +EXPORT_SYMBOL_GPL(media_device_put); >> diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h >> new file mode 100644 >> index 0000000..a63dfc6 >> --- /dev/null >> +++ b/include/media/media-dev-allocator.h >> @@ -0,0 +1,118 @@ >> +/* >> + * media-dev-allocator.h - Media Controller Device Allocator API >> + * >> + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com> >> + * Copyright (c) 2016 Samsung Electronics Co., Ltd. >> + * >> + * This file is released under the GPLv2. >> + * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com> >> + */ >> + >> +/* >> + * This file adds a global ref-counted 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. >> +*/ >> + >> +#ifndef _MEDIA_DEV_ALLOCTOR_H >> +#define _MEDIA_DEV_ALLOCTOR_H >> + >> +struct usb_device; >> + >> +#ifdef CONFIG_MEDIA_CONTROLLER >> +/** >> + * DOC: Media Controller Device Allocator API >> + * >> + * When media device belongs to more than one driver, the shared media device >> + * is allocated with the shared struct device as the key for look ups. >> + * >> + * Shared media device should stay in registered state until the last driver >> + * unregisters it. In addition, media device should be released when all the >> + * references are released. Each driver gets a reference to the media device >> + * during probe, when it allocates the media device. If media device is already >> + * allocated, allocate API bumps up the refcount and return the existing media >> + * device. Driver puts the reference back from its disconnect routine when it >> + * calls media_device_unregister_put(). >> + * >> + * Media device is unregistered and cleaned up from the kref put handler to >> + * ensure that the media device stays in registered state until the last driver >> + * unregisters the media device. >> + * >> + * Media Device can be in any the following states: >> + * >> + * - Allocated > > I don't think this is a real state. It's either unregistered or allocated and > registered. Just 'allocated' doesn't really make sense. This ties in to my > comment about media_device_allocate(). > >> + * - Registered (could be tied to more than one driver) >> + * - Unregistered and released in the kref put handler. > > I would probably drop these 5 lines altogether. > >> + * >> + * Driver Usage: >> + * >> + * Drivers should use the media-core routines to get register reference and >> + * use the media_device_unregister_put() routine to make sure the shared >> + * media device delete is handled correctly. >> + * >> + * driver probe: >> + * Call media_device_usb_allocate() to allocate or get a reference >> + * Call media_device_register(), if media devnode isn't registered >> + * >> + * driver disconnect: >> + * Call media_device_unregister_put() to put the reference. > > There is no media_device_unregister_put() (yet). That should be in the > next patch. > >> + * >> + */ >> + >> +/** >> + * media_device_usb_allocate() - Allocate and return media device >> + * >> + * @udev - struct usb_device pointer >> + * @driver_name >> + * >> + * This interface should be called to allocate a media device when multiple >> + * drivers share usb_device and the media device. This interface allocates >> + * media device and calls media_device_usb_init() to initialize it. >> + * >> + */ >> +struct media_device *media_device_usb_allocate(struct usb_device *udev, >> + char *driver_name); >> +/** >> + * media_device_allocate() - Allocate and return global media device >> + * >> + * @dev - struct device pointer >> + * >> + * This interface should be called to allocate media device. A new media >> + * device instance is created and added to the system wide media device >> + * instance list. If media device instance exists, media_device_allocate() >> + * increments the reference count and returns the media device. When more >> + * than one driver control the media device, the first driver to probe will >> + * allocate and the second driver when it calls media_device_allocate(), >> + * it will get a reference. >> + * >> + */ >> +struct media_device *media_device_allocate(struct device *dev); >> +/** >> + * media_device_get() - Get reference to a registered media device. >> + * >> + * @mdev - struct media_device pointer >> + * >> + * This interface should be called to get a reference to an allocated media >> + * device. >> + */ >> +struct media_device *media_device_get(struct media_device *mdev); >> +/** >> + * media_device_put() - Release media device. Calls kref_put(). >> + * >> + * @mdev - struct media_device pointer >> + * >> + * This interface should be called to put Media Device Instance kref. >> + */ >> +void media_device_put(struct media_device *mdev); >> +#else >> +static inline struct media_device *media_device_usb_allocate( >> + struct usb_device *udev, char *driver_name) >> + { return NULL; } >> +static inline struct media_device *media_device_allocate(struct device *dev) >> + { return NULL; } >> +static inline struct media_device *media_device_get(struct media_device *mdev) >> + { return NULL; } >> +static inline void media_device_put(struct media_device *mdev) { } >> +#endif /* CONFIG_MEDIA_CONTROLLER */ >> +#endif >> > > Regards, > > Hans > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/media/Makefile b/drivers/media/Makefile index e608bbc..b08f091 100644 --- a/drivers/media/Makefile +++ b/drivers/media/Makefile @@ -2,7 +2,8 @@ # Makefile for the kernel multimedia device drivers. # -media-objs := media-device.o media-devnode.o media-entity.o +media-objs := media-device.o media-devnode.o media-entity.o \ + media-dev-allocator.o # # I2C drivers should come before other drivers, otherwise they'll fail diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c new file mode 100644 index 0000000..b49ab55 --- /dev/null +++ b/drivers/media/media-dev-allocator.c @@ -0,0 +1,139 @@ +/* + * media-dev-allocator.c - Media Controller Device Allocator API + * + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com> + * Copyright (c) 2016 Samsung Electronics Co., Ltd. + * + * This file is released under the GPLv2. + * 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/slab.h> +#include <linux/kref.h> +#include <linux/usb.h> +#include <media/media-device.h> + +static LIST_HEAD(media_device_list); +static DEFINE_MUTEX(media_device_lock); + +struct media_device_instance { + struct media_device mdev; + struct list_head list; + struct device *dev; + 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: mdev=%p\n", __func__, &mdi->mdev); + + 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); +} + +static struct media_device *__media_device_get(struct device *dev, + bool allocate) +{ + struct media_device_instance *mdi; + + mutex_lock(&media_device_lock); + + list_for_each_entry(mdi, &media_device_list, list) { + if (mdi->dev == dev) { + kref_get(&mdi->refcount); + dev_dbg(dev, "%s: get mdev=%p\n", + __func__, &mdi->mdev); + goto done; + } + } + + if (!allocate) { + mdi = NULL; + goto done; + } + + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); + if (!mdi) + goto done; + + mdi->dev = dev; + kref_init(&mdi->refcount); + list_add_tail(&mdi->list, &media_device_list); + + dev_dbg(dev, "%s: alloc mdev=%p\n", __func__, &mdi->mdev); + +done: + mutex_unlock(&media_device_lock); + + return mdi ? &mdi->mdev : NULL; +} + +struct media_device *media_device_allocate(struct device *dev) +{ + dev_dbg(dev, "%s\n", __func__); + return __media_device_get(dev, true); +} +EXPORT_SYMBOL_GPL(media_device_allocate); + +struct media_device *media_device_usb_allocate(struct usb_device *udev, + char *driver_name) +{ + struct media_device *mdev; + + mdev = media_device_allocate(&udev->dev); + if (!mdev) + return ERR_PTR(-ENOMEM); + + /* check if media device is already initialized */ + mutex_lock(&media_device_lock); + if (!mdev->dev) + __media_device_usb_init(mdev, udev, udev->product, + driver_name); + mutex_unlock(&media_device_lock); + + return mdev; +} +EXPORT_SYMBOL_GPL(media_device_usb_allocate); + +/* don't allocate - get reference if one is found */ +struct media_device *media_device_get(struct media_device *mdev) +{ + struct media_device_instance *mdi = to_media_device_instance(mdev); + + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); + return __media_device_get(mdi->dev, false); +} +EXPORT_SYMBOL_GPL(media_device_get); + +void media_device_put(struct media_device *mdev) +{ + struct media_device_instance *mdi = to_media_device_instance(mdev); + + dev_dbg(mdi->mdev.dev, "%s: mdev=%p\n", __func__, &mdi->mdev); + kref_put(&mdi->refcount, media_device_instance_release); +} +EXPORT_SYMBOL_GPL(media_device_put); diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h new file mode 100644 index 0000000..a63dfc6 --- /dev/null +++ b/include/media/media-dev-allocator.h @@ -0,0 +1,118 @@ +/* + * media-dev-allocator.h - Media Controller Device Allocator API + * + * Copyright (c) 2016 Shuah Khan <shuahkh@osg.samsung.com> + * Copyright (c) 2016 Samsung Electronics Co., Ltd. + * + * This file is released under the GPLv2. + * Credits: Suggested by Laurent Pinchart <laurent.pinchart@ideasonboard.com> + */ + +/* + * This file adds a global ref-counted 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. +*/ + +#ifndef _MEDIA_DEV_ALLOCTOR_H +#define _MEDIA_DEV_ALLOCTOR_H + +struct usb_device; + +#ifdef CONFIG_MEDIA_CONTROLLER +/** + * DOC: Media Controller Device Allocator API + * + * When media device belongs to more than one driver, the shared media device + * is allocated with the shared struct device as the key for look ups. + * + * Shared media device should stay in registered state until the last driver + * unregisters it. In addition, media device should be released when all the + * references are released. Each driver gets a reference to the media device + * during probe, when it allocates the media device. If media device is already + * allocated, allocate API bumps up the refcount and return the existing media + * device. Driver puts the reference back from its disconnect routine when it + * calls media_device_unregister_put(). + * + * Media device is unregistered and cleaned up from the kref put handler to + * ensure that the media device stays in registered state until the last driver + * unregisters the media device. + * + * Media Device can be in any the following states: + * + * - Allocated + * - Registered (could be tied to more than one driver) + * - Unregistered and released in the kref put handler. + * + * Driver Usage: + * + * Drivers should use the media-core routines to get register reference and + * use the media_device_unregister_put() routine to make sure the shared + * media device delete is handled correctly. + * + * driver probe: + * Call media_device_usb_allocate() to allocate or get a reference + * Call media_device_register(), if media devnode isn't registered + * + * driver disconnect: + * Call media_device_unregister_put() to put the reference. + * + */ + +/** + * media_device_usb_allocate() - Allocate and return media device + * + * @udev - struct usb_device pointer + * @driver_name + * + * This interface should be called to allocate a media device when multiple + * drivers share usb_device and the media device. This interface allocates + * media device and calls media_device_usb_init() to initialize it. + * + */ +struct media_device *media_device_usb_allocate(struct usb_device *udev, + char *driver_name); +/** + * media_device_allocate() - Allocate and return global media device + * + * @dev - struct device pointer + * + * This interface should be called to allocate media device. A new media + * device instance is created and added to the system wide media device + * instance list. If media device instance exists, media_device_allocate() + * increments the reference count and returns the media device. When more + * than one driver control the media device, the first driver to probe will + * allocate and the second driver when it calls media_device_allocate(), + * it will get a reference. + * + */ +struct media_device *media_device_allocate(struct device *dev); +/** + * media_device_get() - Get reference to a registered media device. + * + * @mdev - struct media_device pointer + * + * This interface should be called to get a reference to an allocated media + * device. + */ +struct media_device *media_device_get(struct media_device *mdev); +/** + * media_device_put() - Release media device. Calls kref_put(). + * + * @mdev - struct media_device pointer + * + * This interface should be called to put Media Device Instance kref. + */ +void media_device_put(struct media_device *mdev); +#else +static inline struct media_device *media_device_usb_allocate( + struct usb_device *udev, char *driver_name) + { return NULL; } +static inline struct media_device *media_device_allocate(struct device *dev) + { return NULL; } +static inline struct media_device *media_device_get(struct media_device *mdev) + { return NULL; } +static inline void media_device_put(struct media_device *mdev) { } +#endif /* CONFIG_MEDIA_CONTROLLER */ +#endif
Media Device Allocator API to allows multiple drivers share a media device. Using this API, drivers can allocate a media device with the shared struct device as the key. Once the media device is allocated by a driver, other drivers can get a reference to it. The media device is released when all the references are released. Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com> --- drivers/media/Makefile | 3 +- drivers/media/media-dev-allocator.c | 139 ++++++++++++++++++++++++++++++++++++ include/media/media-dev-allocator.h | 118 ++++++++++++++++++++++++++++++ 3 files changed, 259 insertions(+), 1 deletion(-) create mode 100644 drivers/media/media-dev-allocator.c create mode 100644 include/media/media-dev-allocator.h