[media] media: Media device
The media_device structure abstracts functions common to all kind of media devices (v4l2, dvb, alsa, ...). It manages media entities and offers a userspace API to discover and configure the media device internal topology. Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> Acked-by: Hans Verkuil <hverkuil@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Laurent Pinchart
Mauro Carvalho Chehab
parent
cf4b9211b5
commit
176fb0d108
8 changed files with 304 additions and 1 deletions
6
Documentation/ABI/testing/sysfs-bus-media
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6
Documentation/ABI/testing/sysfs-bus-media
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@ -0,0 +1,6 @@
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What: /sys/bus/media/devices/.../model
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Date: January 2011
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Contact: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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linux-media@vger.kernel.org
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Description: Contains the device model name in UTF-8. The device version is
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is not be appended to the model name.
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@ -327,6 +327,8 @@
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<!ENTITY sub-media-entities SYSTEM "media-entities.tmpl">
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<!ENTITY sub-media-indices SYSTEM "media-indices.tmpl">
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<!ENTITY sub-media-controller SYSTEM "v4l/media-controller.xml">
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<!-- Function Reference -->
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<!ENTITY close SYSTEM "v4l/func-close.xml">
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<!ENTITY ioctl SYSTEM "v4l/func-ioctl.xml">
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@ -106,6 +106,9 @@ Foundation. A copy of the license is included in the chapter entitled
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&sub-remote_controllers;
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</chapter>
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</part>
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<part id="media_common">
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&sub-media-controller;
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</part>
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&sub-fdl-appendix;
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56
Documentation/DocBook/v4l/media-controller.xml
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Documentation/DocBook/v4l/media-controller.xml
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@ -0,0 +1,56 @@
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<partinfo>
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<authorgroup>
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<author>
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<firstname>Laurent</firstname>
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<surname>Pinchart</surname>
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<affiliation><address><email>laurent.pinchart@ideasonboard.com</email></address></affiliation>
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<contrib>Initial version.</contrib>
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</author>
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</authorgroup>
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<copyright>
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<year>2010</year>
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<holder>Laurent Pinchart</holder>
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</copyright>
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<revhistory>
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<!-- Put document revisions here, newest first. -->
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<revision>
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<revnumber>1.0.0</revnumber>
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<date>2010-11-10</date>
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<authorinitials>lp</authorinitials>
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<revremark>Initial revision</revremark>
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</revision>
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</revhistory>
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</partinfo>
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<title>Media Controller API</title>
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<chapter id="media_controller">
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<title>Media Controller</title>
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<section id="media-controller-intro">
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<title>Introduction</title>
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<para>Media devices increasingly handle multiple related functions. Many USB
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cameras include microphones, video capture hardware can also output video,
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or SoC camera interfaces also perform memory-to-memory operations similar to
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video codecs.</para>
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<para>Independent functions, even when implemented in the same hardware, can
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be modelled as separate devices. A USB camera with a microphone will be
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presented to userspace applications as V4L2 and ALSA capture devices. The
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devices' relationships (when using a webcam, end-users shouldn't have to
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manually select the associated USB microphone), while not made available
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directly to applications by the drivers, can usually be retrieved from
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sysfs.</para>
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<para>With more and more advanced SoC devices being introduced, the current
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approach will not scale. Device topologies are getting increasingly complex
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and can't always be represented by a tree structure. Hardware blocks are
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shared between different functions, creating dependencies between seemingly
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unrelated devices.</para>
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<para>Kernel abstraction APIs such as V4L2 and ALSA provide means for
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applications to access hardware parameters. As newer hardware expose an
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increasingly high number of those parameters, drivers need to guess what
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applications really require based on limited information, thereby
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implementing policies that belong to userspace.</para>
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<para>The media controller API aims at solving those problems.</para>
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</section>
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</chapter>
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67
Documentation/media-framework.txt
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67
Documentation/media-framework.txt
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@ -0,0 +1,67 @@
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Linux kernel media framework
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============================
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This document describes the Linux kernel media framework, its data structures,
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functions and their usage.
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Introduction
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------------
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The media controller API is documented in DocBook format in
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Documentation/DocBook/v4l/media-controller.xml. This document will focus on
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the kernel-side implementation of the media framework.
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Media device
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------------
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A media device is represented by a struct media_device instance, defined in
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include/media/media-device.h. Allocation of the structure is handled by the
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media device driver, usually by embedding the media_device instance in a
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larger driver-specific structure.
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Drivers register media device instances by calling
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media_device_register(struct media_device *mdev);
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The caller is responsible for initializing the media_device structure before
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registration. The following fields must be set:
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- dev must point to the parent device (usually a pci_dev, usb_interface or
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platform_device instance).
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- model must be filled with the device model name as a NUL-terminated UTF-8
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string. The device/model revision must not be stored in this field.
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The following fields are optional:
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- serial is a unique serial number stored as a NUL-terminated ASCII string.
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The field is big enough to store a GUID in text form. If the hardware
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doesn't provide a unique serial number this field must be left empty.
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- bus_info represents the location of the device in the system as a
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NUL-terminated ASCII string. For PCI/PCIe devices bus_info must be set to
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"PCI:" (or "PCIe:") followed by the value of pci_name(). For USB devices,
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the usb_make_path() function must be used. This field is used by
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applications to distinguish between otherwise identical devices that don't
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provide a serial number.
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- hw_revision is the hardware device revision in a driver-specific format.
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When possible the revision should be formatted with the KERNEL_VERSION
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macro.
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- driver_version is formatted with the KERNEL_VERSION macro. The version
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minor must be incremented when new features are added to the userspace API
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without breaking binary compatibility. The version major must be
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incremented when binary compatibility is broken.
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Upon successful registration a character device named media[0-9]+ is created.
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The device major and minor numbers are dynamic. The model name is exported as
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a sysfs attribute.
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Drivers unregister media device instances by calling
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media_device_unregister(struct media_device *mdev);
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Unregistering a media device that hasn't been registered is *NOT* safe.
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@ -2,7 +2,7 @@
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# Makefile for the kernel multimedia device drivers.
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#
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media-objs := media-devnode.o
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media-objs := media-device.o media-devnode.o
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ifeq ($(CONFIG_MEDIA_CONTROLLER),y)
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obj-$(CONFIG_MEDIA_SUPPORT) += media.o
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100
drivers/media/media-device.c
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100
drivers/media/media-device.c
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/*
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* Media device
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*
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* Copyright (C) 2010 Nokia Corporation
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*
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* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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* Sakari Ailus <sakari.ailus@iki.fi>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include <linux/types.h>
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#include <linux/ioctl.h>
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#include <media/media-device.h>
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#include <media/media-devnode.h>
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static const struct media_file_operations media_device_fops = {
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.owner = THIS_MODULE,
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};
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/* -----------------------------------------------------------------------------
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* sysfs
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*/
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static ssize_t show_model(struct device *cd,
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struct device_attribute *attr, char *buf)
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{
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struct media_device *mdev = to_media_device(to_media_devnode(cd));
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return sprintf(buf, "%.*s\n", (int)sizeof(mdev->model), mdev->model);
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}
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static DEVICE_ATTR(model, S_IRUGO, show_model, NULL);
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/* -----------------------------------------------------------------------------
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* Registration/unregistration
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*/
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static void media_device_release(struct media_devnode *mdev)
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{
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}
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/**
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* media_device_register - register a media device
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* @mdev: The media device
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*
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* The caller is responsible for initializing the media device before
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* registration. The following fields must be set:
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*
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* - dev must point to the parent device
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* - model must be filled with the device model name
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*/
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int __must_check media_device_register(struct media_device *mdev)
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{
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int ret;
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if (WARN_ON(mdev->dev == NULL || mdev->model[0] == 0))
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return -EINVAL;
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/* Register the device node. */
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mdev->devnode.fops = &media_device_fops;
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mdev->devnode.parent = mdev->dev;
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mdev->devnode.release = media_device_release;
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ret = media_devnode_register(&mdev->devnode);
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if (ret < 0)
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return ret;
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ret = device_create_file(&mdev->devnode.dev, &dev_attr_model);
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if (ret < 0) {
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media_devnode_unregister(&mdev->devnode);
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return ret;
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}
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return 0;
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}
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EXPORT_SYMBOL_GPL(media_device_register);
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/**
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* media_device_unregister - unregister a media device
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* @mdev: The media device
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*
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*/
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void media_device_unregister(struct media_device *mdev)
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{
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device_remove_file(&mdev->devnode.dev, &dev_attr_model);
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media_devnode_unregister(&mdev->devnode);
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}
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EXPORT_SYMBOL_GPL(media_device_unregister);
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69
include/media/media-device.h
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69
include/media/media-device.h
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/*
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* Media device
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*
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* Copyright (C) 2010 Nokia Corporation
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*
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* Contacts: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
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* Sakari Ailus <sakari.ailus@iki.fi>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#ifndef _MEDIA_DEVICE_H
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#define _MEDIA_DEVICE_H
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#include <linux/device.h>
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#include <linux/list.h>
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#include <media/media-devnode.h>
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/**
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* struct media_device - Media device
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* @dev: Parent device
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* @devnode: Media device node
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* @model: Device model name
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* @serial: Device serial number (optional)
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* @bus_info: Unique and stable device location identifier
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* @hw_revision: Hardware device revision
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* @driver_version: Device driver version
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*
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* This structure represents an abstract high-level media device. It allows easy
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* access to entities and provides basic media device-level support. The
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* structure can be allocated directly or embedded in a larger structure.
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*
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* The parent @dev is a physical device. It must be set before registering the
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* media device.
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*
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* @model is a descriptive model name exported through sysfs. It doesn't have to
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* be unique.
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*/
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struct media_device {
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/* dev->driver_data points to this struct. */
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struct device *dev;
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struct media_devnode devnode;
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char model[32];
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char serial[40];
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char bus_info[32];
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u32 hw_revision;
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u32 driver_version;
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};
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/* media_devnode to media_device */
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#define to_media_device(node) container_of(node, struct media_device, devnode)
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int __must_check media_device_register(struct media_device *mdev);
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void media_device_unregister(struct media_device *mdev);
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#endif
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