[alsa-devel] [PATCH v5 1/3] media: Media Device Allocator API
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 Reviewed-by: Hans Verkuil hans.verkuil@cisco.com --- Changes to patch 0001 since v4: - Addressed Sakari's review comments with the exception of opting to not introduce media_device_usb_allocate() macro, and to not add a new routine to find media device instance to avoid a one line check.
Documentation/media/kapi/mc-core.rst | 2 + drivers/media/Makefile | 3 +- drivers/media/media-dev-allocator.c | 135 +++++++++++++++++++++++++++++++++++ include/media/media-dev-allocator.h | 88 +++++++++++++++++++++++ 4 files changed, 227 insertions(+), 1 deletion(-) create mode 100644 drivers/media/media-dev-allocator.c create mode 100644 include/media/media-dev-allocator.h
diff --git a/Documentation/media/kapi/mc-core.rst b/Documentation/media/kapi/mc-core.rst index 1a738e5..0b9090d 100644 --- a/Documentation/media/kapi/mc-core.rst +++ b/Documentation/media/kapi/mc-core.rst @@ -262,3 +262,5 @@ in the end provide a way to use driver-specific callbacks. .. kernel-doc:: include/media/media-devnode.h
.. kernel-doc:: include/media/media-entity.h + +.. kernel-doc:: include/media/media-dev-allocator.h diff --git a/drivers/media/Makefile b/drivers/media/Makefile index 0deaa93..7c0701d 100644 --- a/drivers/media/Makefile +++ b/drivers/media/Makefile @@ -6,7 +6,8 @@ ifeq ($(CONFIG_MEDIA_CEC_EDID),y) obj-$(CONFIG_MEDIA_SUPPORT) += cec-edid.o endif
-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..581e50e --- /dev/null +++ b/drivers/media/media-dev-allocator.c @@ -0,0 +1,135 @@ +/* + * 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/kref.h> +#include <linux/module.h> +#include <linux/slab.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 module *owner; + 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); +} + +/* Callers should hold media_device_lock when calling this function */ +static struct media_device *__media_device_get(struct device *dev, + char *module_name) +{ + struct media_device_instance *mdi; + + list_for_each_entry(mdi, &media_device_list, list) { + if (mdi->dev != dev) + continue; + + kref_get(&mdi->refcount); + /* get module reference for the media_device owner */ + if (find_module(module_name) != mdi->owner && + !try_module_get(mdi->owner)) + dev_err(dev, "%s: try_module_get() error\n", __func__); + dev_dbg(dev, "%s: get mdev=%p module_name %s\n", + __func__, &mdi->mdev, module_name); + return &mdi->mdev; + } + + mdi = kzalloc(sizeof(*mdi), GFP_KERNEL); + if (!mdi) + return NULL; + + mdi->dev = dev; + mdi->owner = find_module(module_name); + kref_init(&mdi->refcount); + list_add_tail(&mdi->list, &media_device_list); + + dev_dbg(dev, "%s: alloc mdev=%p module_name %s\n", __func__, + &mdi->mdev, module_name); + return &mdi->mdev; +} + +#if IS_ENABLED(CONFIG_USB) +struct media_device *media_device_usb_allocate(struct usb_device *udev, + char *module_name) +{ + struct media_device *mdev; + + mutex_lock(&media_device_lock); + mdev = __media_device_get(&udev->dev, module_name); + 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); +#endif + +void media_device_delete(struct media_device *mdev, char *module_name) +{ + struct media_device_instance *mdi = to_media_device_instance(mdev); + + dev_dbg(mdi->mdev.dev, "%s: mdev=%p module_name %s\n", + __func__, &mdi->mdev, module_name); + + mutex_lock(&media_device_lock); + /* put module reference if media_device owner is not THIS_MODULE */ + if (mdi->owner != find_module(module_name)) { + module_put(mdi->owner); + dev_dbg(mdi->mdev.dev, + "%s decremented owner module reference\n", __func__); + } + mutex_unlock(&media_device_lock); + kref_put(&mdi->refcount, media_device_instance_release); +} +EXPORT_SYMBOL_GPL(media_device_delete); diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h new file mode 100644 index 0000000..fad8cb9 --- /dev/null +++ b/include/media/media-dev-allocator.h @@ -0,0 +1,88 @@ +/* + * 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 +/** + * 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_delete(). + * + * 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. + * + * Driver Usage: + * + * Drivers should use the media-core routines to get register reference and + * call media_device_delete() 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_delete() to free the media_device. Free'ing is + * handled by the put handler. + * + */ + +/** + * media_device_usb_allocate() - Allocate and return media device + * + * @udev: struct usb_device pointer + * @module_name: should be filled with KBUILD_MODNAME + * + * 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 structure and calls media_device_usb_init() to initialize + * it. + * + */ +struct media_device *media_device_usb_allocate(struct usb_device *udev, + char *module_name); +/** + * media_device_delete() - Release media device. Calls kref_put(). + * + * @mdev: struct media_device pointer + * @module_name: should be filled with KBUILD_MODNAME + * + * This interface should be called to put Media Device Instance kref. + */ +void media_device_delete(struct media_device *mdev, char *driver_name); +#else +static inline struct media_device *media_device_usb_allocate( + struct usb_device *udev, char *driver_name) + { return NULL; } +static inline void media_device_delete( + struct media_device *mdev, char *module_name) { } +#endif /* CONFIG_MEDIA_CONTROLLER */ +#endif
Em Fri, 18 Nov 2016 14:45:10 -0700 Shuah Khan shuahkh@osg.samsung.com escreveu:
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 Reviewed-by: Hans Verkuil hans.verkuil@cisco.com
Changes to patch 0001 since v4:
- Addressed Sakari's review comments with the exception of opting to not introduce media_device_usb_allocate() macro, and to not add a new routine to find media device instance to avoid a one line check.
Documentation/media/kapi/mc-core.rst | 2 + drivers/media/Makefile | 3 +- drivers/media/media-dev-allocator.c | 135 +++++++++++++++++++++++++++++++++++ include/media/media-dev-allocator.h | 88 +++++++++++++++++++++++ 4 files changed, 227 insertions(+), 1 deletion(-) create mode 100644 drivers/media/media-dev-allocator.c create mode 100644 include/media/media-dev-allocator.h
diff --git a/Documentation/media/kapi/mc-core.rst b/Documentation/media/kapi/mc-core.rst index 1a738e5..0b9090d 100644 --- a/Documentation/media/kapi/mc-core.rst +++ b/Documentation/media/kapi/mc-core.rst @@ -262,3 +262,5 @@ in the end provide a way to use driver-specific callbacks. .. kernel-doc:: include/media/media-devnode.h
.. kernel-doc:: include/media/media-entity.h
+.. kernel-doc:: include/media/media-dev-allocator.h diff --git a/drivers/media/Makefile b/drivers/media/Makefile index 0deaa93..7c0701d 100644 --- a/drivers/media/Makefile +++ b/drivers/media/Makefile @@ -6,7 +6,8 @@ ifeq ($(CONFIG_MEDIA_CEC_EDID),y) obj-$(CONFIG_MEDIA_SUPPORT) += cec-edid.o endif
-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..581e50e --- /dev/null +++ b/drivers/media/media-dev-allocator.c @@ -0,0 +1,135 @@ +/*
- 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/kref.h> +#include <linux/module.h> +#include <linux/slab.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 module *owner;
- struct list_head list;
- struct device *dev;
I agree with Sakari here: mdev is embedded. So, it will always have a mdev.dev inside it. So, if dev == mdev.dev for all cases, we can just get rid of it. If you want to simplify the code, just add a to_dev() macro like:
#define to_dev(mdi) (mdi)->mdev.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);
+}
+/* Callers should hold media_device_lock when calling this function */ +static struct media_device *__media_device_get(struct device *dev,
char *module_name)+{
- struct media_device_instance *mdi;
- list_for_each_entry(mdi, &media_device_list, list) {
if (mdi->dev != dev)continue;kref_get(&mdi->refcount);/* get module reference for the media_device owner */if (find_module(module_name) != mdi->owner &&!try_module_get(mdi->owner))dev_err(dev, "%s: try_module_get() error\n", __func__);dev_dbg(dev, "%s: get mdev=%p module_name %s\n",__func__, &mdi->mdev, module_name);return &mdi->mdev;- }
- mdi = kzalloc(sizeof(*mdi), GFP_KERNEL);
- if (!mdi)
return NULL;- mdi->dev = dev;
- mdi->owner = find_module(module_name);
- kref_init(&mdi->refcount);
- list_add_tail(&mdi->list, &media_device_list);
- dev_dbg(dev, "%s: alloc mdev=%p module_name %s\n", __func__,
&mdi->mdev, module_name);- return &mdi->mdev;
+}
+#if IS_ENABLED(CONFIG_USB) +struct media_device *media_device_usb_allocate(struct usb_device *udev,
char *module_name)+{
- struct media_device *mdev;
- mutex_lock(&media_device_lock);
- mdev = __media_device_get(&udev->dev, module_name);
- 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);
It misses variant for PCI drivers. Ok, we could postpone it until we have the need of using media device allocator on pci drivers.
- mutex_unlock(&media_device_lock);
- return mdev;
+} +EXPORT_SYMBOL_GPL(media_device_usb_allocate); +#endif
+void media_device_delete(struct media_device *mdev, char *module_name) +{
- struct media_device_instance *mdi = to_media_device_instance(mdev);
- dev_dbg(mdi->mdev.dev, "%s: mdev=%p module_name %s\n",
__func__, &mdi->mdev, module_name);- mutex_lock(&media_device_lock);
- /* put module reference if media_device owner is not THIS_MODULE */
- if (mdi->owner != find_module(module_name)) {
module_put(mdi->owner);dev_dbg(mdi->mdev.dev,"%s decremented owner module reference\n", __func__);- }
- mutex_unlock(&media_device_lock);
- kref_put(&mdi->refcount, media_device_instance_release);
+} +EXPORT_SYMBOL_GPL(media_device_delete); diff --git a/include/media/media-dev-allocator.h b/include/media/media-dev-allocator.h new file mode 100644 index 0000000..fad8cb9 --- /dev/null +++ b/include/media/media-dev-allocator.h @@ -0,0 +1,88 @@ +/*
- 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 +/**
- Media Controller Device Allocator API
Huh? kernel-doc won't work with this. Did you test this patch with the media documentation, by calling: make DOCBOOKS="" SPHINXOPTS="-j9" SPHINXDIRS=media htmldocs
Also, as I said before: please move those textual descriptions to Documentation/media/kapi/mc-core.rst, and use ReST markup to enrich it and add cross-references to functions and data structs mentioned below.
- 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_delete().
- 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.
- Driver Usage:
- Drivers should use the media-core routines to get register reference and
- call media_device_delete() 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_delete() to free the media_device. Free'ing is
- handled by the put handler.
- */
+/**
- media_device_usb_allocate() - Allocate and return media device
- @udev: struct usb_device pointer
- @module_name: should be filled with KBUILD_MODNAME
- 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 structure and calls media_device_usb_init() to initialize
- it.
- */
+struct media_device *media_device_usb_allocate(struct usb_device *udev,
char *module_name);+/**
- media_device_delete() - Release media device. Calls kref_put().
- @mdev: struct media_device pointer
- @module_name: should be filled with KBUILD_MODNAME
- This interface should be called to put Media Device Instance kref.
- */
+void media_device_delete(struct media_device *mdev, char *driver_name); +#else +static inline struct media_device *media_device_usb_allocate(
struct usb_device *udev, char *driver_name){ return NULL; }+static inline void media_device_delete(
struct media_device *mdev, char *module_name) { }+#endif /* CONFIG_MEDIA_CONTROLLER */ +#endif
Thanks, Mauro
participants (2)
-
Mauro Carvalho Chehab -
Shuah Khan