V4L/DVB (11242): allow v4l2 drivers to provide a get_unmapped_area handler

Shared memory mappings on nommu machines require a get_unmapped_area
file operation that suggests an address for the mapping. This patch
adds a way for v4l2 drivers to provide this callback.
Signed-off-by: Daniel Glöckner <dg@emlix.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/v4l2-dev.c

@@ -198,6 +198,23 @@ static long v4l2_unlocked_ioctl(struct file *filp,
 	return vdev->fops->unlocked_ioctl(filp, cmd, arg);
 }
 
+#ifdef CONFIG_MMU
+#define v4l2_get_unmapped_area NULL
+#else
+static unsigned long v4l2_get_unmapped_area(struct file *filp,
+		unsigned long addr, unsigned long len, unsigned long pgoff,
+		unsigned long flags)
+{
+	struct video_device *vdev = video_devdata(filp);
+
+	if (!vdev->fops->get_unmapped_area)
+		return -ENOSYS;
+	if (video_is_unregistered(vdev))
+		return -ENODEV;
+	return vdev->fops->get_unmapped_area(filp, addr, len, pgoff, flags);
+}
+#endif
+
 static int v4l2_mmap(struct file *filp, struct vm_area_struct *vm)
 {
 	struct video_device *vdev = video_devdata(filp);
@@ -250,6 +267,7 @@ static const struct file_operations v4l2_unlocked_fops = {
 	.read = v4l2_read,
 	.write = v4l2_write,
 	.open = v4l2_open,
+	.get_unmapped_area = v4l2_get_unmapped_area,
 	.mmap = v4l2_mmap,
 	.unlocked_ioctl = v4l2_unlocked_ioctl,
 #ifdef CONFIG_COMPAT
@@ -265,6 +283,7 @@ static const struct file_operations v4l2_fops = {
 	.read = v4l2_read,
 	.write = v4l2_write,
 	.open = v4l2_open,
+	.get_unmapped_area = v4l2_get_unmapped_area,
 	.mmap = v4l2_mmap,
 	.ioctl = v4l2_ioctl,
 #ifdef CONFIG_COMPAT

include/media/v4l2-dev.h

@@ -40,6 +40,8 @@ struct v4l2_file_operations {
 	unsigned int (*poll) (struct file *, struct poll_table_struct *);
 	long (*ioctl) (struct file *, unsigned int, unsigned long);
 	long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
+	unsigned long (*get_unmapped_area) (struct file *, unsigned long,
+				unsigned long, unsigned long, unsigned long);
 	int (*mmap) (struct file *, struct vm_area_struct *);
 	int (*open) (struct file *);
 	int (*release) (struct file *);