From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965188AbaD2TuT (ORCPT ); Tue, 29 Apr 2014 15:50:19 -0400 Received: from qmta09.emeryville.ca.mail.comcast.net ([76.96.30.96]:35675 "EHLO qmta09.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965168AbaD2TuP (ORCPT ); Tue, 29 Apr 2014 15:50:15 -0400 From: Shuah Khan To: gregkh@linuxfoundation.org, m.chehab@samsung.com, tj@kernel.org, olebowle@gmx.com Cc: Shuah Khan , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org Subject: [PATCH 1/4] drivers/base: add managed token devres interfaces Date: Tue, 29 Apr 2014 13:49:23 -0600 Message-Id: <6cb20ce23f540c883e60e6ce71302042b034c4aa.1398797955.git.shuah.kh@samsung.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Media devices often have hardware resources that are shared across several functions. These devices appear as a group of independent devices. Each device implements a function which could be shared by one or more functions supported by the same device. For example, tuner is shared by analog and digital TV functions. Media drivers that control a single media TV stick are a diversified group. Analog and digital TV function drivers have to coordinate access to their shared functions. Some media devices provide multiple almost-independent functions. USB and PCI core aids in allowwing multiple drivers to handle these almost-independent functions. In this model, a em28xx device could have snd-usb-audio driving the audio function. As a result, snd-usb-audio driver has to coordinate with the em28xx_* analog and digital function drivers. A shared managed resource framework at drivers/base level will allow a media device to be controlled by drivers that don't fall under drivers/media and share functions with other media drivers. A token devres that can be looked up by a token for locking, try locking, unlocking will help avoid adding data structure dependencies between various drivers. This token is a unique string that can be constructed from a common data structure such as struct device, bus_name, and hardware address. The devm_token_* interfaces manage access to token resource. Interfaces: devm_token_create() devm_token_destroy() devm_token_lock() devm_token_unlock() Usage: Create token: Call devm_token_create() with a token id string. Lock token: Call devm_token_lock() to lock or try lock a token. Unlock token: Call devm_token_unlock(). Destroy token: Call devm_token_destroy() to delete the token. Signed-off-by: Shuah Khan --- drivers/base/Makefile | 2 +- drivers/base/token_devres.c | 146 ++++++++++++++++++++++++++++++++++++++++++ include/linux/token_devres.h | 19 ++++++ 3 files changed, 166 insertions(+), 1 deletion(-) create mode 100644 drivers/base/token_devres.c create mode 100644 include/linux/token_devres.h diff --git a/drivers/base/Makefile b/drivers/base/Makefile index 04b314e..924665b 100644 --- a/drivers/base/Makefile +++ b/drivers/base/Makefile @@ -4,7 +4,7 @@ obj-y := component.o core.o bus.o dd.o syscore.o \ driver.o class.o platform.o \ cpu.o firmware.o init.o map.o devres.o \ attribute_container.o transport_class.o \ - topology.o container.o + topology.o container.o token_devres.o obj-$(CONFIG_DEVTMPFS) += devtmpfs.o obj-$(CONFIG_DMA_CMA) += dma-contiguous.o obj-y += power/ diff --git a/drivers/base/token_devres.c b/drivers/base/token_devres.c new file mode 100644 index 0000000..4644642 --- /dev/null +++ b/drivers/base/token_devres.c @@ -0,0 +1,146 @@ +/* + * drivers/base/token_devres.c - managed token resource + * + * Copyright (c) 2014 Shuah Khan + * Copyright (c) 2014 Samsung Electronics Co., Ltd. + * + * This file is released under the GPLv2. + */ +/* + * Media devices often have hardware resources that are shared + * across several functions. For instance, TV tuner cards often + * have MUXes, converters, radios, tuners, etc. that are shared + * across various functions. However, v4l2, alsa, DVB, usbfs, and + * all other drivers have no knowledge of what resources are + * shared. For example, users can't access DVB and alsa at the same + * time, or the DVB and V4L analog API at the same time, since many + * only have one converter that can be in either analog or digital + * mode. Accessing and/or changing mode of a converter while it is + * in use by another function results in video stream error. + * + * A shared devres that can be locked and unlocked by various drivers + * that control media functions on a single media device is needed to + * address the above problems. + * + * A token devres that can be looked up by a token for locking, try + * locking, unlocking will help avoid adding data structure + * dependencies between various media drivers. This token is a unique + * string that can be constructed from a common data structure such as + * struct device, bus_name, and hardware address. + * + * The devm_token_* interfaces manage access to token resource. + * + * Interfaces: + * devm_token_create() + * devm_token_destroy() + * devm_token_lock() + * devm_token_unlock() + * Usage: + * Create token: + * Call devm_token_create() with a token id which is + * a unique string. + * Lock token: + * Call devm_token_lock() to lock or try lock a token. + * Unlock token: + * Call devm_token_unlock(). + * Destroy token: + * Call devm_token_destroy() to delete the token. + * +*/ +#include +#include + +struct token_devres { + struct mutex lock; + bool in_use; + char id[]; +}; + +static int devm_token_match(struct device *dev, void *res, void *data) +{ + struct token_devres *tkn = res; + + /* compare the token data and return 1 if it matches */ + return !strcmp(tkn->id, data); +} + +static void devm_token_release(struct device *dev, void *res) +{ + struct token_devres *tkn = res; + + mutex_destroy(&tkn->lock); +} + +/* creates a token devres and marks it available */ +int devm_token_create(struct device *dev, const char *id) +{ + struct token_devres *tkn; + size_t tkn_size; + + tkn_size = sizeof(struct token_devres) + strlen(id) + 1; + tkn = devres_alloc(devm_token_release, tkn_size, GFP_KERNEL); + if (!tkn) + return -ENOMEM; + + strcpy(tkn->id, id); + tkn->in_use = false; + mutex_init(&tkn->lock); + + devres_add(dev, tkn); + return 0; +} +EXPORT_SYMBOL_GPL(devm_token_create); + +/* If token is available, lock it for the caller, If not return -EBUSY */ +int devm_token_lock(struct device *dev, const char *id) +{ + struct token_devres *tkn_ptr; + int rc = 0; + + tkn_ptr = devres_find(dev, devm_token_release, devm_token_match, + (void *)id); + if (tkn_ptr == NULL) + return -ENODEV; + + if (!mutex_trylock(&tkn_ptr->lock)) + return -EBUSY; + + if (tkn_ptr->in_use) + rc = -EBUSY; + else + tkn_ptr->in_use = true; + + mutex_unlock(&tkn_ptr->lock); + return rc; +} +EXPORT_SYMBOL_GPL(devm_token_lock); + +/* If token is locked, unlock */ +int devm_token_unlock(struct device *dev, const char *id) +{ + struct token_devres *tkn_ptr; + + tkn_ptr = devres_find(dev, devm_token_release, devm_token_match, + (void *) id); + if (tkn_ptr == NULL) + return -ENODEV; + + mutex_lock(&tkn_ptr->lock); + tkn_ptr->in_use = false; + mutex_unlock(&tkn_ptr->lock); + return 0; +} +EXPORT_SYMBOL_GPL(devm_token_unlock); + +/* destroy an existing token */ +int devm_token_destroy(struct device *dev, const char *id) +{ + int rc; + + rc = devres_release(dev, devm_token_release, devm_token_match, + (void *) id); + WARN_ON(rc); + + return 0; +} +EXPORT_SYMBOL_GPL(devm_token_destroy); diff --git a/include/linux/token_devres.h b/include/linux/token_devres.h new file mode 100644 index 0000000..e411fd5 --- /dev/null +++ b/include/linux/token_devres.h @@ -0,0 +1,19 @@ +/* + * token_devres.h - managed token resource + * + * Copyright (c) 2014 Shuah Khan + * Copyright (c) 2014 Samsung Electronics Co., Ltd. + * + * This file is released under the GPLv2. + */ +#ifndef __LINUX_TOKEN_DEVRES_H +#define __LINUX_TOKEN_DEVRES_H + +struct device; + +extern int devm_token_create(struct device *dev, const char *id); +extern int devm_token_lock(struct device *dev, const char *id); +extern int devm_token_unlock(struct device *dev, const char *id); +extern int devm_token_destroy(struct device *dev, const char *id); + +#endif /* __LINUX_TOKEN_DEVRES_H */ -- 1.7.10.4