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[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>
This commit is contained in:
Andy Walls 2011-01-26 21:25:47 -03:00 committed by Mauro Carvalho Chehab
parent 12d896e1c1
commit 9b28500a59
1 changed files with 1 additions and 31 deletions
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32
drivers/staging/lirc/lirc_zilog.c
View File

@ -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;