From patchwork Wed Mar 27 02:24:48 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shuah X-Patchwork-Id: 10872397 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 84D071669 for ; Wed, 27 Mar 2019 02:25:22 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 6EAEF27FA9 for ; Wed, 27 Mar 2019 02:25:22 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 62A4328B9C; Wed, 27 Mar 2019 02:25:22 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 8700727FA9 for ; Wed, 27 Mar 2019 02:25:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732715AbfC0CY7 (ORCPT ); Tue, 26 Mar 2019 22:24:59 -0400 Received: from mail.kernel.org ([198.145.29.99]:36808 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731571AbfC0CY6 (ORCPT ); Tue, 26 Mar 2019 22:24:58 -0400 Received: from shuah-t480s.internal (c-24-9-64-241.hsd1.co.comcast.net [24.9.64.241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 88E4D2146E; Wed, 27 Mar 2019 02:24:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553653497; bh=qjJRpFiljckmmG2rqFmj5LP0eMlcjdUzy7BFEspY2jQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=bGr3dDtBRuvulmTrCcWr1OldCsKdS7o6P0TBCanSQ7yBBe0soG6csk7NvKkbBPT9y vPKR4Co9MvnnktCMoQQtxky/4jNvPNynPNCSPbfqYQubyKmqmjPceX6/f+qY6YOPQa 31yT0EZ5VnHE1CTid72pbsj/oj7la24Cn7Rd6NWA= From: Shuah Khan To: mchehab@kernel.org, perex@perex.cz, tiwai@suse.com, hverkuil@xs4all.nl Cc: Shuah Khan , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, alsa-devel@alsa-project.org Subject: [PATCH v12 1/5] media: Media Device Allocator API Date: Tue, 26 Mar 2019 20:24:48 -0600 Message-Id: <1e22c34b011c3c1fd793a623fb59c82081d46038.1553634246.git.shuah@kernel.org> X-Mailer: git-send-email 2.19.1 In-Reply-To: References: MIME-Version: 1.0 Sender: linux-media-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-media@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Media Device Allocator API to allows multiple drivers share a media device. This API solves a very common use-case for media devices where one physical device (an USB stick) provides both audio and video. When such media device exposes a standard USB Audio class, a proprietary Video class, two or more independent drivers will share a single physical USB bridge. In such cases, it is necessary to coordinate access to the shared resource. 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 --- Documentation/media/kapi/mc-core.rst | 41 ++++++++ drivers/media/Makefile | 6 ++ drivers/media/media-dev-allocator.c | 142 +++++++++++++++++++++++++++ include/media/media-dev-allocator.h | 54 ++++++++++ 4 files changed, 243 insertions(+) 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 f930725e0d6b..05bba0b61748 100644 --- a/Documentation/media/kapi/mc-core.rst +++ b/Documentation/media/kapi/mc-core.rst @@ -259,6 +259,45 @@ Subsystems should facilitate link validation by providing subsystem specific helper functions to provide easy access for commonly needed information, and in the end provide a way to use driver-specific callbacks. +Media Controller Device Allocator API +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +When the 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. + +The shared media device should stay in registered state until the last +driver unregisters it. In addition, the 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, the allocate API bumps up the refcount and returns the +existing media device. The driver puts the reference back in its disconnect +routine when it calls :c:func:`media_device_delete()`. + +The 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 appropriate media-core routines to manage the shared +media device life-time handling the two states: +1. allocate -> register -> delete +2. get reference to already registered device -> delete + +call :c:func:`media_device_delete()` routine to make sure the shared media +device delete is handled correctly. + +**driver probe:** +Call :c:func:`media_device_usb_allocate()` to allocate or get a reference +Call :c:func:`media_device_register()`, if media devnode isn't registered + +**driver disconnect:** +Call :c:func:`media_device_delete()` to free the media_device. Freeing is +handled by the kref put handler. + +API Definitions +^^^^^^^^^^^^^^^ + .. kernel-doc:: include/media/media-device.h .. kernel-doc:: include/media/media-devnode.h @@ -266,3 +305,5 @@ in the end provide a way to use driver-specific callbacks. .. kernel-doc:: include/media/media-entity.h .. kernel-doc:: include/media/media-request.h + +.. kernel-doc:: include/media/media-dev-allocator.h diff --git a/drivers/media/Makefile b/drivers/media/Makefile index 985d35ec6b29..20b488067ec2 100644 --- a/drivers/media/Makefile +++ b/drivers/media/Makefile @@ -6,6 +6,12 @@ media-objs := media-device.o media-devnode.o media-entity.o \ media-request.o +ifeq ($(CONFIG_USB),y) + ifeq ($(CONFIG_MODULES),y) + media-objs += media-dev-allocator.o + endif +endif + # # I2C drivers should come before other drivers, otherwise they'll fail # when compiled as builtin drivers diff --git a/drivers/media/media-dev-allocator.c b/drivers/media/media-dev-allocator.c new file mode 100644 index 000000000000..a37515254009 --- /dev/null +++ b/drivers/media/media-dev-allocator.c @@ -0,0 +1,142 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * media-dev-allocator.c - Media Controller Device Allocator API + * + * Copyright (c) 2018 Shuah Khan + * + * Credits: Suggested by Laurent Pinchart + */ + +/* + * 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 +#include +#include +#include + +#include + +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: 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, + const char *module_name, + struct module *modp) +{ + 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 (modp != 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->owner = modp; + 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; +} + +struct media_device *media_device_usb_allocate(struct usb_device *udev, + const char *module_name) +{ + struct media_device *mdev; + struct module *modptr; + + mutex_lock(&module_mutex); + modptr = find_module(module_name); + mutex_unlock(&module_mutex); + + mutex_lock(&media_device_lock); + mdev = __media_device_get(&udev->dev, module_name, modptr); + 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 media_device_instance *mdi = to_media_device_instance(mdev); + struct module *modptr; + + dev_dbg(mdi->mdev.dev, "%s: mdev=%p module_name %s\n", + __func__, &mdi->mdev, module_name); + + mutex_lock(&module_mutex); + modptr = find_module(module_name); + mutex_unlock(&module_mutex); + + mutex_lock(&media_device_lock); + /* put module reference if media_device owner is not THIS_MODULE */ + if (mdi->owner != modptr) { + 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 000000000000..69aee9a4b4c1 --- /dev/null +++ b/include/media/media-dev-allocator.h @@ -0,0 +1,54 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * media-dev-allocator.h - Media Controller Device Allocator API + * + * Copyright (c) 2018 Shuah Khan + * + * Credits: Suggested by Laurent Pinchart + */ + +/* + * 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; + +#if defined(CONFIG_MEDIA_CONTROLLER) && defined(CONFIG_USB) && \ + defined(CONFIG_MODULES) +/** + * media_device_usb_allocate() - Allocate and return struct &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 *module_name); +#else +static inline struct media_device *media_device_usb_allocate( + struct usb_device *udev, char *module_name) + { return NULL; } +static inline void media_device_delete( + struct media_device *mdev, char *module_name) { } +#endif /* CONFIG_MEDIA_CONTROLLER && CONFIG_USB && CONFIG_MODULES */ +#endif