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@xxxxxxxxxxxxxxxx>
---
Documentation/media-framework.txt | 91 ++++++++++++++++++++++++++++++++++
drivers/media/Makefile | 2 +-
drivers/media/media-device.c | 98 +++++++++++++++++++++++++++++++++++++
include/media/media-device.h | 64 ++++++++++++++++++++++++
4 files changed, 254 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..89dc7ad
--- /dev/null
+++ b/Documentation/media-framework.txt
@@ -0,0 +1,91 @@
+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 must point to the parent device (usually a pci_dev, usb_interface or
+ platform_device instance).
+
+ - model must be filled with the device model name as a NUL-terminated UTF-8
+ string. The device/model revision must not be stored in this field.
+
+The following fields are optional:
+
+ - serial is a unique serial number stored as an ASCII string. The string must
+ be NUL-terminated unless exactly 32 characters long. This allows storing
+ GUIDs in a text form. If the hardware doesn't provide a unique serial
+ number this field must be left empty.
+
+ - bus_info represents the location of the device in the system as a
+ NUL-terminated ASCII string. For PCI/PCIe devices bus_info must be set to
+ "PCI:" (or "PCIe:") followed by the value of pci_name(). For USB devices,
+ the usb_make_path() function must be used. This field is used by
+ applications to distinguish between otherwise identical devices that don't
+ provide a serial number.
+
+ - device_version is the hardware device version number in a driver-specific
+ format. When possible the version should be formatted with the
+ KERNEL_VERSION macro.
+
+ - driver_version is formatted with the KERNEL_VERSION macro. The version
+ minor must be incremented when new features are added to the userspace API
+ without breaking binary compatibility. The version major must be
+ incremented when binary compatibility is broken.
+
+Upon successful registration a character device named media[0-9]+ is created.
+The device major and minor numbers are dynamic. The model name is exported as
+a sysfs attribute.
+
+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..781c641
--- /dev/null
+++ b/drivers/media/media-device.c
@@ -0,0 +1,98 @@
+/*
+ * Media device support.
+ *
+ * Copyright (C) 2010 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
+ *
+ * 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,
+};
+
+/* -----------------------------------------------------------------------------
+ * sysfs
+ */
+
+static ssize_t show_model(struct device *cd,
+ struct device_attribute *attr, char *buf)
+{
+ struct media_device *mdev = to_media_device(to_media_devnode(cd));
+
+ return sprintf(buf, "%.*s\n", (int)sizeof(mdev->model), mdev->model);
+}
+
+static DEVICE_ATTR(model, S_IRUGO, show_model, NULL);
+
+/* -----------------------------------------------------------------------------
+ * Registration/unregistration
+ */
+
+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 must point to the parent device
+ * - model must be filled with the device model name
+ */
+int __must_check media_device_register(struct media_device *mdev)
+{
+ int ret;
+
+ if (WARN_ON(mdev->dev == NULL || mdev->model[0] == 0))
+ return 0;
+
+ /* Register the device node. */
+ mdev->devnode.fops = &media_device_fops;
+ mdev->devnode.parent = mdev->dev;
+ mdev->devnode.release = media_device_release;
+ ret = media_devnode_register(&mdev->devnode);
+ if (ret < 0)
+ return ret;
+
+ ret = device_create_file(&mdev->devnode.dev, &dev_attr_model);
+ if (ret < 0) {
+ media_devnode_unregister(&mdev->devnode);
+ return ret;
+ }
+
+ return 0;
+}
+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)
+{
+ device_remove_file(&mdev->devnode.dev, &dev_attr_model);
+ 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..4fe949e
--- /dev/null
+++ b/include/media/media-device.h
@@ -0,0 +1,64 @@
+/*
+ * Media device support header.
+ *
+ * Copyright (C) 2010 Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
+ *
+ * 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>
+
+/**
+ * struct media_device - Media device
+ * @dev: Parent device
+ * @devnode: Media device node
+ * @model: Device model name
+ * @serial: Device serial number (optional)
+ * @bus_info: Unique and stable device location identifier
+ * @device_version: Hardware device version
+ * @driver_version: Device driver version
+ *
+ * This structure represents an abstract high-level media device. It allows easy
+ * access to entities and provides basic media device-level support. The
+ * structure can be allocated directly or embedded in a larger structure.
+ *
+ * The parent @dev is a physical device. It must be set before registering the
+ * media device.
+ *
+ * @model is a descriptive model name exported through sysfs. It doesn't have to
+ * be unique.
+ */
+struct media_device {
+ /* dev->driver_data points to this struct. */
+ struct device *dev;
+ struct media_devnode devnode;
+
+ u8 model[32];
+ u8 serial[32];
+ u8 bus_info[32];
+ u32 device_version;
+ u32 driver_version;
+};
+
+int __must_check media_device_register(struct media_device *mdev);
+void media_device_unregister(struct media_device *mdev);
+
+#endif
--
1.7.1
--
To unsubscribe from this list: send the line "unsubscribe linux-media" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
