[media] lirc_zilog: Remove broken, ineffective reference counting

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>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

diff --git a/drivers/staging/lirc/lirc_zilog.c b/drivers/staging/lirc/lirc_zilog.c
index 7389b77ece8c8ac81bb78200f15dd24304af8f39..3a912575e12d6910e0bf3e3bd1b79dee6f74f45e 100644 (file)
--- 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;