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.pinch...@ideasonboard.com>
---
Documentation/media-framework.txt | 68 +++++++++++++++++++++++++++++++++
drivers/media/Makefile | 2 +-
drivers/media/media-device.c | 76 +++++++++++++++++++++++++++++++++++++
include/media/media-device.h | 48 +++++++++++++++++++++++
4 files changed, 193 insertions(+), 1 deletions(-)
create mode 100644 Documentation/media-framework.txt
create mode 100644 drivers/media/media-device.c
create mode 100644 include/media/media-device.h
diff --git a/Documentation/media-framework.txt
b/Documentation/media-framework.txt
new file mode 100644
index 0000000..b942c8f
--- /dev/null
+++ b/Documentation/media-framework.txt
@@ -0,0 +1,68 @@
+Linux kernel media framework
+============================
+
+This document describes the Linux kernel media framework, its data structures,
+functions and their usage.
+
+
+Introduction
+------------
+
+Media devices increasingly handle multiple related functions. Many USB cameras
+include microphones, video capture hardware can also output video, or SoC
+camera interfaces also perform memory-to-memory operations similar to video
+codecs.
+
+Independent functions, even when implemented in the same hardware, can be
+modeled by separate devices. A USB camera with a microphone will be presented
+to userspace applications as V4L2 and ALSA capture devices. The devices
+relationships (when using a webcam, end-users shouldn't have to manually
+select the associated USB microphone), while not made available directly to
+applications by the drivers, can usually be retrieved from sysfs.
+
+With more and more advanced SoC devices being introduced, the current approach
+will not scale. Device topologies are getting increasingly complex and can't
+always be represented by a tree structure. Hardware blocks are shared between
+different functions, creating dependencies between seemingly unrelated
+devices.
+
+Kernel abstraction APIs such as V4L2 and ALSA provide means for applications
+to access hardware parameters. As newer hardware expose an increasingly high
+number of those parameters, drivers need to guess what applications really
+require based on limited information, thereby implementing policies that
+belong to userspace.
+
+The media kernel API aims at solving those problems.
+
+
+Media device
+------------
+
+A media device is represented by a struct media_device instance, defined in
+include/media/media-device.h. Allocation of the structure is handled by the
+media device driver, usually by embedding the media_device instance in a
+larger driver-specific structure.
+
+Drivers register media device instances by calling
+
+ media_device_register(struct media_device *mdev);
+
+The caller is responsible for initializing the media_device structure before
+registration. The following fields must be set:
+
+ - dev should point to the parent device (usually a pci_dev, usb_interface or
+ platform_device instance). In the rare case when no parent device is
+ available (with ISA devices for instance), the field can be set to NULL.
+ - name should be set to the device name. If the name is empty a parent device
+ must be set. In that case the name will be set to the parent device driver
+ name followed by a space and the parent device name.
+
+Upon successful registration a character device named media[0-9]+ is created.
+The device major and minor numbers are dynamic.
+
+Drivers unregister media device instances by calling
+
+ media_device_unregister(struct media_device *mdev);
+
+Unregistering a media device that hasn't been registered is *NOT* safe.
+
diff --git a/drivers/media/Makefile b/drivers/media/Makefile
index c1b5938..f8d8dcb 100644
--- a/drivers/media/Makefile
+++ b/drivers/media/Makefile
@@ -2,7 +2,7 @@
# Makefile for the kernel multimedia device drivers.
#
-media-objs := media-devnode.o
+media-objs := media-device.o media-devnode.o
obj-$(CONFIG_MEDIA_SUPPORT) += media.o
diff --git a/drivers/media/media-device.c b/drivers/media/media-device.c
new file mode 100644
index 0000000..75eaccd
--- /dev/null
+++ b/drivers/media/media-device.c
@@ -0,0 +1,76 @@
+/*
+ * Media device support.
+ *
+ * Copyright (C) 2010 Laurent Pinchart <laurent.pinch...@ideasonboard.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/types.h>
+#include <linux/ioctl.h>
+
+#include <media/media-device.h>
+#include <media/media-devnode.h>
+
+static const struct media_file_operations media_device_fops = {
+ .owner = THIS_MODULE,
+};
+
+static void media_device_release(struct media_devnode *mdev)
+{
+}
+
+/**
+ * media_device_register - register a media device
+ * @mdev: The media device
+ *
+ * The caller is responsible for initializing the media device before
+ * registration. The following fields must be set:
+ *
+ * - dev should point to the parent device. The field can be NULL when no
+ * parent device is available (for instance with ISA devices).
+ * - devnode.name should be set to the device name. If the name is empty a
+ * parent device must be set. In that case the name will be set to the parent
+ * device driver name followed by a space and the parent device name.
+ */
+int __must_check media_device_register(struct media_device *mdev)
+{
+ /* If dev == NULL, then name must be filled in by the caller */
+ if (mdev->dev == NULL && WARN_ON(!mdev->devnode.name[0]))
+ return 0;
+
+ /* Set name to driver name + device name if it is empty. */
+ if (!mdev->devnode.name[0])
+ snprintf(mdev->devnode.name, sizeof(mdev->devnode.name),
+ "%s %s", mdev->dev->driver->name, dev_name(mdev->dev));
+
+ /* Register the device node. */
+ mdev->devnode.fops = &media_device_fops;
+ mdev->devnode.parent = mdev->dev;
+ mdev->devnode.release = media_device_release;
+ return media_devnode_register(&mdev->devnode);
+}
+EXPORT_SYMBOL_GPL(media_device_register);
+
+/**
+ * media_device_unregister - unregister a media device
+ * @mdev: The media device
+ *
+ */
+void media_device_unregister(struct media_device *mdev)
+{
+ media_devnode_unregister(&mdev->devnode);
+}
+EXPORT_SYMBOL_GPL(media_device_unregister);
diff --git a/include/media/media-device.h b/include/media/media-device.h
new file mode 100644
index 0000000..bd559b0
--- /dev/null
+++ b/include/media/media-device.h
@@ -0,0 +1,48 @@
+/*
+ * Media device support header.
+ *
+ * Copyright (C) 2010 Laurent Pinchart <laurent.pinch...@ideasonboard.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#ifndef _MEDIA_DEVICE_H
+#define _MEDIA_DEVICE_H
+
+#include <linux/device.h>
+#include <linux/list.h>
+
+#include <media/media-devnode.h>
+
+/* Each instance of a media device should create the media_device struct,
+ * either stand-alone or embedded in a larger struct.
+ *
+ * It allows easy access to sub-devices (see v4l2-subdev.h) and provides
+ * basic media device-level support.
+ */
+
+struct media_device {
+ /* dev->driver_data points to this struct.
+ * Note: dev might be NULL if there is no parent device
+ * as is the case with e.g. ISA devices.
+ */
+ struct device *dev;
+ struct media_devnode devnode;
+};
+
+int __must_check media_device_register(struct media_device *mdev);
+void media_device_unregister(struct media_device *mdev);
+
+#endif
--
1.7.1
--
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