From 169316cd4fa882d232b112eda1fbeff217446b7d Mon Sep 17 00:00:00 2001
From: Sandor Yu <R01008@freescale.com>
Date: Tue, 1 Sep 2015 15:15:48 +0800
Subject: [PATCH] MLK-11508-1: Revert "[media] v4l2-core: remove the old .ioctl
 BKL replacement"

This reverts commit 5cf6f7f327c95f09be859889be39e78950516556.
---
 drivers/media/v4l2-core/v4l2-dev.c    | 28 +++++++++++++++++++++++++++
 drivers/media/v4l2-core/v4l2-device.c |  1 +
 include/media/v4l2-dev.h              |  1 +
 include/media/v4l2-device.h           |  2 ++
 4 files changed, 32 insertions(+)

diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index fe5581c0eaeb..206cff6b0c97 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -360,6 +360,34 @@ static long v4l2_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			ret = vdev->fops->unlocked_ioctl(filp, cmd, arg);
 		if (lock)
 			mutex_unlock(lock);
+	} else if (vdev->fops->ioctl) {
+		/* This code path is a replacement for the BKL. It is a major
+		 * hack but it will have to do for those drivers that are not
+		 * yet converted to use unlocked_ioctl.
+		 *
+		 * All drivers implement struct v4l2_device, so we use the
+		 * lock defined there to serialize the ioctls.
+		 *
+		 * However, if the driver sleeps, then it blocks all ioctls
+		 * since the lock is still held. This is very common for
+		 * VIDIOC_DQBUF since that normally waits for a frame to arrive.
+		 * As a result any other ioctl calls will proceed very, very
+		 * slowly since each call will have to wait for the VIDIOC_QBUF
+		 * to finish. Things that should take 0.01s may now take 10-20
+		 * seconds.
+		 *
+		 * The workaround is to *not* take the lock for VIDIOC_DQBUF.
+		 * This actually works OK for videobuf-based drivers, since
+		 * videobuf will take its own internal lock.
+		 */
+		struct mutex *m = &vdev->v4l2_dev->ioctl_lock;
+
+		if (cmd != VIDIOC_DQBUF && mutex_lock_interruptible(m))
+			return -ERESTARTSYS;
+		if (video_is_registered(vdev))
+			ret = vdev->fops->ioctl(filp, cmd, arg);
+		if (cmd != VIDIOC_DQBUF)
+			mutex_unlock(m);
 	} else
 		ret = -ENOTTY;
 
diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
index 62bbed76dbbc..e4d15ee44a6d 100644
--- a/drivers/media/v4l2-core/v4l2-device.c
+++ b/drivers/media/v4l2-core/v4l2-device.c
@@ -37,6 +37,7 @@ int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
 
 	INIT_LIST_HEAD(&v4l2_dev->subdevs);
 	spin_lock_init(&v4l2_dev->lock);
+	mutex_init(&v4l2_dev->ioctl_lock);
 	v4l2_prio_init(&v4l2_dev->prio);
 	kref_init(&v4l2_dev->ref);
 	get_device(dev);
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index e657614521e3..252bd3dae53f 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -152,6 +152,7 @@ struct v4l2_file_operations {
 	ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
 	ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
 	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);
 #ifdef CONFIG_COMPAT
 	long (*compat_ioctl32) (struct file *, unsigned int, unsigned long);
diff --git a/include/media/v4l2-device.h b/include/media/v4l2-device.h
index 8ffa94009d1a..bb97f64e91c8 100644
--- a/include/media/v4l2-device.h
+++ b/include/media/v4l2-device.h
@@ -69,6 +69,8 @@ struct v4l2_device {
 			unsigned int notification, void *arg);
 	struct v4l2_ctrl_handler *ctrl_handler;
 	struct v4l2_prio_state prio;
+	/* BKL replacement mutex. Temporary solution only. */
+	struct mutex ioctl_lock;
 	struct kref ref;
 	void (*release)(struct v4l2_device *v4l2_dev);
 };