[PATCH 02/13] lirc_zilog: Remove broken, ineffective reference counting

[Andy Walls <awalls@md.metrocast.net>]

The set_use_inc() and set_use_dec() functions tried to lock
the underlying bridge driver device instance in memory by
changing the use count on the device's i2c_clients.  This
worked for PCI devices (ivtv, cx18, bttv).  It doesn't
work for hot-pluggable usb devices (pvrusb2 and hdpvr).
With usb device instances, the driver may get locked into
memory, but the unplugged hardware is gone.

The set_use_inc() set_use_dec() functions also tried to have
lirc_zilog change its own module refernce count, which is
racy and not guaranteed to work.  The lirc_dev module does
actually perform proper module ref count manipulation on the
lirc_zilog module, so there is need for lirc_zilog to
attempt a buggy module get on itself anyway.

lirc_zilog also errantly called these functions on itself
in open() and close(), but lirc_dev did that already too.

So let's just gut the bodies of the set_use_*() functions,
and remove the extra calls to them from within lirc_zilog.

Proper reference counting of the struct IR, IR_rx, and IR_tx
objects -- to handle the case when the underlying
bttv, ivtv, cx18, hdpvr, or pvrusb2 bridge driver module or
device instance goes away -- will be added in subsequent
patches.

Signed-off-by: Andy Walls <awalls@md.metrocast.net>
---
 drivers/staging/lirc/lirc_zilog.c |   32 +-------------------------------
 1 files changed, 1 insertions(+), 31 deletions(-)

diff --git a/drivers/staging/lirc/lirc_zilog.c b/drivers/staging/lirc/lirc_zilog.c
index 7389b77..3a91257 100644
--- a/drivers/staging/lirc/lirc_zilog.c
+++ b/drivers/staging/lirc/lirc_zilog.c
@@ -305,34 +305,12 @@ static int lirc_thread(void *arg)
 
 static int set_use_inc(void *data)
 {
-	struct IR *ir = data;
-
-	if (ir->l.owner == NULL || try_module_get(ir->l.owner) == 0)
-		return -ENODEV;
-
-	/* lock bttv in memory while /dev/lirc is in use  */
-	/*
-	 * this is completely broken code. lirc_unregister_driver()
-	 * must be possible even when the device is open
-	 */
-	if (ir->rx != NULL)
-		i2c_use_client(ir->rx->c);
-	if (ir->tx != NULL)
-		i2c_use_client(ir->tx->c);
-
 	return 0;
 }
 
 static void set_use_dec(void *data)
 {
-	struct IR *ir = data;
-
-	if (ir->rx)
-		i2c_release_client(ir->rx->c);
-	if (ir->tx)
-		i2c_release_client(ir->tx->c);
-	if (ir->l.owner != NULL)
-		module_put(ir->l.owner);
+	return;
 }
 
 /* safe read of a uint32 (always network byte order) */
@@ -1098,7 +1076,6 @@ static struct IR *find_ir_device_by_minor(unsigned int minor)
 static int open(struct inode *node, struct file *filep)
 {
 	struct IR *ir;
-	int ret;
 	unsigned int minor = MINOR(node->i_rdev);
 
 	/* find our IR struct */
@@ -1112,12 +1089,6 @@ static int open(struct inode *node, struct file *filep)
 	/* increment in use count */
 	mutex_lock(&ir->ir_lock);
 	++ir->open;
-	ret = set_use_inc(ir);
-	if (ret != 0) {
-		--ir->open;
-		mutex_unlock(&ir->ir_lock);
-		return ret;
-	}
 	mutex_unlock(&ir->ir_lock);
 
 	/* stash our IR struct */
@@ -1139,7 +1110,6 @@ static int close(struct inode *node, struct file *filep)
 	/* decrement in use count */
 	mutex_lock(&ir->ir_lock);
 	--ir->open;
-	set_use_dec(ir);
 	mutex_unlock(&ir->ir_lock);
 
 	return 0;
-- 
1.7.2.1