V4L/DVB: V4L: File handles

This patch adds a list of v4l2_fh structures to every video_device.
It allows using file handle related information in V4L2. The event interface
is one example of such use.

The use of v4l2_fh is not mandatory for drivers.

Signed-off-by: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/Makefile

@@ -10,7 +10,7 @@ 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
+videodev-objs	:=	v4l2-dev.o v4l2-ioctl.o v4l2-device.o v4l2-fh.o
 
 # V4L2 core modules
 

drivers/media/video/v4l2-dev.c

@@ -421,6 +421,10 @@ static int __video_register_device(struct video_device *vdev, int type, int nr,
 	if (!vdev->release)
 		return -EINVAL;
 
+	/* v4l2_fh support */
+	spin_lock_init(&vdev->fh_lock);
+	INIT_LIST_HEAD(&vdev->fh_list);
+
 	/* Part 1: check device type */
 	switch (type) {
 	case VFL_TYPE_GRABBER:

drivers/media/video/v4l2-fh.c

@@ -0,0 +1,66 @@
+/*
+ * v4l2-fh.c
+ *
+ * V4L2 file handles.
+ *
+ * Copyright (C) 2009--2010 Nokia Corporation.
+ *
+ * Contact: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 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., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#include <linux/bitops.h>
+#include <media/v4l2-dev.h>
+#include <media/v4l2-fh.h>
+
+int v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev)
+{
+	fh->vdev = vdev;
+	INIT_LIST_HEAD(&fh->list);
+	set_bit(V4L2_FL_USES_V4L2_FH, &fh->vdev->flags);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(v4l2_fh_init);
+
+void v4l2_fh_add(struct v4l2_fh *fh)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&fh->vdev->fh_lock, flags);
+	list_add(&fh->list, &fh->vdev->fh_list);
+	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
+}
+EXPORT_SYMBOL_GPL(v4l2_fh_add);
+
+void v4l2_fh_del(struct v4l2_fh *fh)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&fh->vdev->fh_lock, flags);
+	list_del_init(&fh->list);
+	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
+}
+EXPORT_SYMBOL_GPL(v4l2_fh_del);
+
+void v4l2_fh_exit(struct v4l2_fh *fh)
+{
+	if (fh->vdev == NULL)
+		return;
+
+	fh->vdev = NULL;
+}
+EXPORT_SYMBOL_GPL(v4l2_fh_exit);

include/media/v4l2-dev.h

@@ -32,6 +32,7 @@ struct v4l2_device;
    Drivers can clear this flag if they want to block all future
    device access. It is cleared by video_unregister_device. */
 #define V4L2_FL_REGISTERED	(0)
+#define V4L2_FL_USES_V4L2_FH	(1)
 
 struct v4l2_file_operations {
 	struct module *owner;
@@ -77,6 +78,10 @@ struct video_device
 	/* attribute to differentiate multiple indices on one physical device */
 	int index;
 
+	/* V4L2 file handles */
+	spinlock_t		fh_lock; /* Lock for all v4l2_fhs */
+	struct list_head	fh_list; /* List of struct v4l2_fh */
+
 	int debug;			/* Activates debug level*/
 
 	/* Video standard vars */

include/media/v4l2-fh.h

@@ -0,0 +1,63 @@
+/*
+ * v4l2-fh.h
+ *
+ * V4L2 file handle. Store per file handle data for the V4L2
+ * framework. Using file handles is optional for the drivers.
+ *
+ * Copyright (C) 2009--2010 Nokia Corporation.
+ *
+ * Contact: Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 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., 51 Franklin St, Fifth Floor, Boston, MA
+ * 02110-1301 USA
+ */
+
+#ifndef V4L2_FH_H
+#define V4L2_FH_H
+
+#include <linux/list.h>
+
+struct video_device;
+
+struct v4l2_fh {
+	struct list_head	list;
+	struct video_device	*vdev;
+};
+
+/*
+ * Initialise the file handle. Parts of the V4L2 framework using the
+ * file handles should be initialised in this function. Must be called
+ * from driver's v4l2_file_operations->open() handler if the driver
+ * uses v4l2_fh.
+ */
+int v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev);
+/*
+ * Add the fh to the list of file handles on a video_device. The file
+ * handle must be initialised first.
+ */
+void v4l2_fh_add(struct v4l2_fh *fh);
+/*
+ * Remove file handle from the list of file handles. Must be called in
+ * v4l2_file_operations->release() handler if the driver uses v4l2_fh.
+ */
+void v4l2_fh_del(struct v4l2_fh *fh);
+/*
+ * Release resources related to a file handle. Parts of the V4L2
+ * framework using the v4l2_fh must release their resources here, too.
+ * Must be called in v4l2_file_operations->release() handler if the
+ * driver uses v4l2_fh.
+ */
+void v4l2_fh_exit(struct v4l2_fh *fh);
+
+#endif /* V4L2_EVENT_H */