[media] v4l: subdev: Add device node support

Create a device node named subdevX for every registered subdev.

As the device node is registered before the subdev core::s_config
function is called, return -EGAIN on open until initialization
completes.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Vimarsh Zutshi <vimarsh.zutshi@gmail.com>
Acked-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/video4linux/v4l2-framework.txt

@@ -319,6 +319,22 @@ controlled through GPIO pins. This distinction is only relevant when setting
 up the device, but once the subdev is registered it is completely transparent.
 
 
+V4L2 sub-device userspace API
+-----------------------------
+
+Beside exposing a kernel API through the v4l2_subdev_ops structure, V4L2
+sub-devices can also be controlled directly by userspace applications.
+
+Device nodes named v4l-subdevX can be created in /dev to access sub-devices
+directly. If a sub-device supports direct userspace configuration it must set
+the V4L2_SUBDEV_FL_HAS_DEVNODE flag before being registered.
+
+After registering sub-devices, the v4l2_device driver can create device nodes
+for all registered sub-devices marked with V4L2_SUBDEV_FL_HAS_DEVNODE by calling
+v4l2_device_register_subdev_nodes(). Those device nodes will be automatically
+removed when sub-devices are unregistered.
+
+
 I2C sub-device drivers
 ----------------------
 

drivers/media/video/Makefile

@@ -11,7 +11,7 @@ stkwebcam-objs	:=	stk-webcam.o stk-sensor.o
 omap2cam-objs	:=	omap24xxcam.o omap24xxcam-dma.o
 
 videodev-objs	:=	v4l2-dev.o v4l2-ioctl.o v4l2-device.o v4l2-fh.o \
-			v4l2-event.o v4l2-ctrls.o
+			v4l2-event.o v4l2-ctrls.o v4l2-subdev.o
 
 # V4L2 core modules
 

drivers/media/video/v4l2-dev.c

@@ -408,13 +408,14 @@ static int get_index(struct video_device *vdev)
 }
 
 /**
- *	video_register_device - register video4linux devices
+ *	__video_register_device - register video4linux devices
  *	@vdev: video device structure we want to register
  *	@type: type of device to register
  *	@nr:   which device node number (0 == /dev/video0, 1 == /dev/video1, ...
  *             -1 == first free)
  *	@warn_if_nr_in_use: warn if the desired device node number
  *	       was already in use and another number was chosen instead.
+ *	@owner: module that owns the video device node
  *
  *	The registration code assigns minor numbers and device node numbers
  *	based on the requested type and registers the new device node with
@@ -435,9 +436,11 @@ static int get_index(struct video_device *vdev)
  *	%VFL_TYPE_VBI - Vertical blank data (undecoded)
  *
  *	%VFL_TYPE_RADIO - A radio card
+ *
+ *	%VFL_TYPE_SUBDEV - A subdevice
  */
-static int __video_register_device(struct video_device *vdev, int type, int nr,
-		int warn_if_nr_in_use)
+int __video_register_device(struct video_device *vdev, int type, int nr,
+		int warn_if_nr_in_use, struct module *owner)
 {
 	int i = 0;
 	int ret;
@@ -469,6 +472,9 @@ static int __video_register_device(struct video_device *vdev, int type, int nr,
 	case VFL_TYPE_RADIO:
 		name_base = "radio";
 		break;
+	case VFL_TYPE_SUBDEV:
+		name_base = "v4l-subdev";
+		break;
 	default:
 		printk(KERN_ERR "%s called with unknown type: %d\n",
 		       __func__, type);
@@ -552,7 +558,7 @@ static int __video_register_device(struct video_device *vdev, int type, int nr,
 		goto cleanup;
 	}
 	vdev->cdev->ops = &v4l2_fops;
-	vdev->cdev->owner = vdev->fops->owner;
+	vdev->cdev->owner = owner;
 	ret = cdev_add(vdev->cdev, MKDEV(VIDEO_MAJOR, vdev->minor), 1);
 	if (ret < 0) {
 		printk(KERN_ERR "%s: cdev_add failed\n", __func__);
@@ -597,18 +603,7 @@ static int __video_register_device(struct video_device *vdev, int type, int nr,
 	vdev->minor = -1;
 	return ret;
 }
-
-int video_register_device(struct video_device *vdev, int type, int nr)
-{
-	return __video_register_device(vdev, type, nr, 1);
-}
-EXPORT_SYMBOL(video_register_device);
-
-int video_register_device_no_warn(struct video_device *vdev, int type, int nr)
-{
-	return __video_register_device(vdev, type, nr, 0);
-}
-EXPORT_SYMBOL(video_register_device_no_warn);
+EXPORT_SYMBOL(__video_register_device);
 
 /**
  *	video_unregister_device - unregister a video4linux device

drivers/media/video/v4l2-device.c

@@ -124,16 +124,20 @@ int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
 	/* Check for valid input */
 	if (v4l2_dev == NULL || sd == NULL || !sd->name[0])
 		return -EINVAL;
+
 	/* Warn if we apparently re-register a subdev */
 	WARN_ON(sd->v4l2_dev != NULL);
+
 	if (!try_module_get(sd->owner))
 		return -ENODEV;
+
 	sd->v4l2_dev = v4l2_dev;
 	if (sd->internal_ops && sd->internal_ops->registered) {
 		err = sd->internal_ops->registered(sd);
 		if (err)
 			return err;
 	}
+
 	/* This just returns 0 if either of the two args is NULL */
 	err = v4l2_ctrl_add_handler(v4l2_dev->ctrl_handler, sd->ctrl_handler);
 	if (err) {
@@ -141,24 +145,57 @@ int v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
 			sd->internal_ops->unregistered(sd);
 		return err;
 	}
+
 	spin_lock(&v4l2_dev->lock);
 	list_add_tail(&sd->list, &v4l2_dev->subdevs);
 	spin_unlock(&v4l2_dev->lock);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_device_register_subdev);
 
+int v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev)
+{
+	struct video_device *vdev;
+	struct v4l2_subdev *sd;
+	int err;
+
+	/* Register a device node for every subdev marked with the
+	 * V4L2_SUBDEV_FL_HAS_DEVNODE flag.
+	 */
+	list_for_each_entry(sd, &v4l2_dev->subdevs, list) {
+		if (!(sd->flags & V4L2_SUBDEV_FL_HAS_DEVNODE))
+			continue;
+
+		vdev = &sd->devnode;
+		strlcpy(vdev->name, sd->name, sizeof(vdev->name));
+		vdev->v4l2_dev = v4l2_dev;
+		vdev->fops = &v4l2_subdev_fops;
+		vdev->release = video_device_release_empty;
+		err = __video_register_device(vdev, VFL_TYPE_SUBDEV, -1, 1,
+					      sd->owner);
+		if (err < 0)
+			return err;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_device_register_subdev_nodes);
+
 void v4l2_device_unregister_subdev(struct v4l2_subdev *sd)
 {
 	/* return if it isn't registered */
 	if (sd == NULL || sd->v4l2_dev == NULL)
 		return;
+
 	spin_lock(&sd->v4l2_dev->lock);
 	list_del(&sd->list);
 	spin_unlock(&sd->v4l2_dev->lock);
 	if (sd->internal_ops && sd->internal_ops->unregistered)
 		sd->internal_ops->unregistered(sd);
 	sd->v4l2_dev = NULL;
+
+	video_unregister_device(&sd->devnode);
 	module_put(sd->owner);
 }
 EXPORT_SYMBOL_GPL(v4l2_device_unregister_subdev);

drivers/media/video/v4l2-subdev.c

+/*
+ *  V4L2 subdevice support.
+ *
+ *  Copyright (C) 2010 Nokia Corporation
+ *
+ *  Contact: Laurent Pinchart <laurent.pinchart@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.
+ *
+ *  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 <linux/videodev2.h>
+
+#include <media/v4l2-device.h>
+#include <media/v4l2-ioctl.h>
+
+static int subdev_open(struct file *file)
+{
+	return 0;
+}
+
+static int subdev_close(struct file *file)
+{
+	return 0;
+}
+
+static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg)
+{
+	switch (cmd) {
+	default:
+		return -ENOIOCTLCMD;
+	}
+
+	return 0;
+}
+
+static long subdev_ioctl(struct file *file, unsigned int cmd,
+	unsigned long arg)
+{
+	return video_usercopy(file, cmd, arg, subdev_do_ioctl);
+}
+
+const struct v4l2_file_operations v4l2_subdev_fops = {
+	.owner = THIS_MODULE,
+	.open = subdev_open,
+	.unlocked_ioctl = subdev_ioctl,
+	.release = subdev_close,
+};

include/media/v4l2-dev.h

@@ -21,7 +21,8 @@
 #define VFL_TYPE_GRABBER	0
 #define VFL_TYPE_VBI		1
 #define VFL_TYPE_RADIO		2
-#define VFL_TYPE_MAX		3
+#define VFL_TYPE_SUBDEV		3
+#define VFL_TYPE_MAX		4
 
 struct v4l2_ioctl_callbacks;
 struct video_device;
@@ -102,15 +103,26 @@ struct video_device
 /* dev to video-device */
 #define to_video_device(cd) container_of(cd, struct video_device, dev)
 
+int __must_check __video_register_device(struct video_device *vdev, int type,
+		int nr, int warn_if_nr_in_use, struct module *owner);
+
 /* Register video devices. Note that if video_register_device fails,
    the release() callback of the video_device structure is *not* called, so
    the caller is responsible for freeing any data. Usually that means that
    you call video_device_release() on failure. */
-int __must_check video_register_device(struct video_device *vdev, int type, int nr);
+static inline int __must_check video_register_device(struct video_device *vdev,
+		int type, int nr)
+{
+	return __video_register_device(vdev, type, nr, 1, vdev->fops->owner);
+}
 
 /* Same as video_register_device, but no warning is issued if the desired
    device node number was already in use. */
-int __must_check video_register_device_no_warn(struct video_device *vdev, int type, int nr);
+static inline int __must_check video_register_device_no_warn(
+		struct video_device *vdev, int type, int nr)
+{
+	return __video_register_device(vdev, type, nr, 0, vdev->fops->owner);
+}
 
 /* Unregister video devices. Will do nothing if vdev == NULL or
    video_is_registered() returns false. */

include/media/v4l2-device.h

@@ -96,6 +96,12 @@ int __must_check v4l2_device_register_subdev(struct v4l2_device *v4l2_dev,
    wasn't registered. In that case it will do nothing. */
 void v4l2_device_unregister_subdev(struct v4l2_subdev *sd);
 
+/* Register device nodes for all subdev of the v4l2 device that are marked with
+ * the V4L2_SUBDEV_FL_HAS_DEVNODE flag.
+ */
+int __must_check
+v4l2_device_register_subdev_nodes(struct v4l2_device *v4l2_dev);
+
 /* Iterate over all subdevs. */
 #define v4l2_device_for_each_subdev(sd, v4l2_dev)			\
 	list_for_each_entry(sd, &(v4l2_dev)->subdevs, list)

include/media/v4l2-subdev.h

@@ -22,6 +22,7 @@
 #define _V4L2_SUBDEV_H
 
 #include <media/v4l2-common.h>
+#include <media/v4l2-dev.h>
 #include <media/v4l2-mediabus.h>
 
 /* generic v4l2_device notify callback notification values */
@@ -434,6 +435,8 @@ struct v4l2_subdev_internal_ops {
 #define V4L2_SUBDEV_FL_IS_I2C			(1U << 0)
 /* Set this flag if this subdev is a spi device. */
 #define V4L2_SUBDEV_FL_IS_SPI			(1U << 1)
+/* Set this flag if this subdev needs a device node. */
+#define V4L2_SUBDEV_FL_HAS_DEVNODE		(1U << 2)
 
 /* Each instance of a subdev driver should create this struct, either
    stand-alone or embedded in a larger struct.
@@ -455,8 +458,15 @@ struct v4l2_subdev {
 	/* pointer to private data */
 	void *dev_priv;
 	void *host_priv;
+	/* subdev device node */
+	struct video_device devnode;
 };
 
+#define vdev_to_v4l2_subdev(vdev) \
+	container_of(vdev, struct v4l2_subdev, devnode)
+
+extern const struct v4l2_file_operations v4l2_subdev_fops;
+
 static inline void v4l2_set_subdevdata(struct v4l2_subdev *sd, void *p)
 {
 	sd->dev_priv = p;