From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964781AbaDIPVd (ORCPT ); Wed, 9 Apr 2014 11:21:33 -0400 Received: from qmta15.emeryville.ca.mail.comcast.net ([76.96.27.228]:47846 "EHLO qmta15.emeryville.ca.mail.comcast.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933389AbaDIPVZ (ORCPT ); Wed, 9 Apr 2014 11:21:25 -0400 From: Shuah Khan To: gregkh@linuxfoundation.org, m.chehab@samsung.com, tj@kernel.org, rafael.j.wysocki@intel.com, linux@roeck-us.net, toshi.kani@hp.com Cc: Shuah Khan , linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, shuahkhan@gmail.com Subject: [RFC PATCH 0/2] managed token devres interfaces Date: Wed, 9 Apr 2014 09:21:06 -0600 Message-Id: X-Mailer: git-send-email 1.8.3.2 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. 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. A new devres_* interface to update the status of this token resource to busy when locked and free when unlocked is necessary to implement this new managed resource. devres_update() searches for the resource that matches supplied match criteria similar to devres_find(). When a match is found, it calls the update function caller passed in. This patch set adds a new devres_update) interface and token devres interfaces. Test Cases for token devres interfaces: (passed) - Create, lock, unlock, and destroy sequence. - Try lock while it is locked. Returns -EBUSY as expected. - Try lock after destroy. Returns -ENODEV as expected. - Unlock while it is unlocked. Returns 0 as expected. This is a no-op. - Try unlock after destroy. Returns -ENODEV as expected. Special notes for Mauro Chehab: - Please evaluate if these token devres interfaces cover all media driver use-cases. If not what is needed to cover them. - For use-case testing, I generated a string from em28xx device, as this is common for all em28xx extensions: (hope this holds true when em28xx uses snd-usb-audio - Construct string with (dev is struct em28xx *dev) format: "tuner:%s-%s-%d" with the following: dev_name(&dev->udev->dev) dev->udev->bus->bus_name dev->tuner_addr - I added test code to em28xx_card_setup() to test the interfaces: example token from this test code generated with the format above: usb 8-1: devm_token_create(): created token: tuner:8-1-0000:00:10.1-0 Shuah Khan (2): drivers/base: add new devres_update() interface to devres_* drivers/base: add managed token devres interfaces drivers/base/Makefile | 2 +- drivers/base/devres.c | 36 ++++++++ drivers/base/token_devres.c | 204 ++++++++++++++++++++++++++++++++++++++++++ include/linux/device.h | 4 + include/linux/token_devres.h | 19 ++++ 5 files changed, 264 insertions(+), 1 deletion(-) create mode 100644 drivers/base/token_devres.c create mode 100644 include/linux/token_devres.h -- 1.7.10.4