Devin Heitmueller wrote:
> On Thu, Apr 1, 2010 at 11:02 AM, Mauro Carvalho Chehab
> <mchehab@xxxxxxxxxx> wrote:
>> I remember I had to do it on em28xx:
>>
>> This is the init code for it:
>> ...
>> mutex_init(&dev->lock);
>> mutex_lock(&dev->lock);
>> em28xx_init_dev(&dev, udev, interface, nr);
>> ...
>> request_modules(dev);
>>
>> /* Should be the last thing to do, to avoid newer udev's to
>> open the device before fully initializing it
>> */
>> mutex_unlock(&dev->lock);
>> ...
>>
>> And this is the open code:
>>
>> static int em28xx_v4l2_open(struct file *filp)
>> {
>> ...
>> mutex_lock(&dev->lock);
>> ...
>> mutex_unlock(&dev->lock);
>>
>
> It's probably worth noting that this change is actually pretty badly
> broken. Because the modules are loading asynchronously, there is a
> high probability that the em28xx-dvb driver will still be loading when
> hald connects in to the v4l device. That's the big reason people
> often see things like tvp5150 i2c errors when the driver is first
> loaded up.
>
> It's a good idea in theory, but pretty fatally flawed due to the async
> loading (as to make it work properly you would have to do something
> like locking the mutex in em28xx and clearing it in em28xx-dvb at the
> end of its initialization).
Devin,
I found some time to fix the above reported issue. Patch follows.
---
V4L/DVB: em28xx: fix locks during dvb init sequence
During em28xx init, em28xx-dvb needs to change to digital mode, in order to
properly initialize. However, as soon as em28xx-video registers /dev/video0,
udev will try to run v4l_id program, to retrieve some information that it is
needed by udev device creation.
So, while v4l_id is opening the /dev/video? device and setting the device in
analog mode, the em28xx-dvb is putting the same device on digital mode, and
trying to initialize the DVB demod.
On devices that have a I2C bridge, this results on one of the devices to not
being accessed, either resulting on I2C error or on wrong readings at devices
like tvp5150.
As the analog operations are protected by dev->lock, the fix is as simple as
locking it also during em28xx-dvb initialization.
While here, also simplifies the locking schema for the extension
register/unregister functions.
Tested on WinTV HVR-950 (2040:6513), doing several sequences of unload/reload.
On all cases, the proper init happened:
[ 1075.497596] tvp5150 2-005c: tvp5150am1 detected.
[ 1075.647916] xc2028 2-0061: attaching existing instance
[ 1075.653106] xc2028 2-0061: type set to XCeive xc2028/xc3028 tuner
[ 1075.659254] em28xx #0: em28xx #0/2: xc3028 attached
Signed-off-by: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
diff --git a/drivers/media/video/em28xx/em28xx-core.c b/drivers/media/video/em28xx/em28xx-core.c
index d4f4525..c8c4e8f 100644
--- a/drivers/media/video/em28xx/em28xx-core.c
+++ b/drivers/media/video/em28xx/em28xx-core.c
@@ -1177,21 +1177,18 @@ void em28xx_add_into_devlist(struct em28xx *dev)
*/
static LIST_HEAD(em28xx_extension_devlist);
-static DEFINE_MUTEX(em28xx_extension_devlist_lock);
int em28xx_register_extension(struct em28xx_ops *ops)
{
struct em28xx *dev = NULL;
mutex_lock(&em28xx_devlist_mutex);
- mutex_lock(&em28xx_extension_devlist_lock);
list_add_tail(&ops->next, &em28xx_extension_devlist);
list_for_each_entry(dev, &em28xx_devlist, devlist) {
if (dev)
ops->init(dev);
}
printk(KERN_INFO "Em28xx: Initialized (%s) extension\n", ops->name);
- mutex_unlock(&em28xx_extension_devlist_lock);
mutex_unlock(&em28xx_devlist_mutex);
return 0;
}
@@ -1207,10 +1204,8 @@ void em28xx_unregister_extension(struct em28xx_ops *ops)
ops->fini(dev);
}
- mutex_lock(&em28xx_extension_devlist_lock);
printk(KERN_INFO "Em28xx: Removed (%s) extension\n", ops->name);
list_del(&ops->next);
- mutex_unlock(&em28xx_extension_devlist_lock);
mutex_unlock(&em28xx_devlist_mutex);
}
EXPORT_SYMBOL(em28xx_unregister_extension);
@@ -1219,26 +1214,26 @@ void em28xx_init_extension(struct em28xx *dev)
{
struct em28xx_ops *ops = NULL;
- mutex_lock(&em28xx_extension_devlist_lock);
+ mutex_lock(&em28xx_devlist_mutex);
if (!list_empty(&em28xx_extension_devlist)) {
list_for_each_entry(ops, &em28xx_extension_devlist, next) {
if (ops->init)
ops->init(dev);
}
}
- mutex_unlock(&em28xx_extension_devlist_lock);
+ mutex_unlock(&em28xx_devlist_mutex);
}
void em28xx_close_extension(struct em28xx *dev)
{
struct em28xx_ops *ops = NULL;
- mutex_lock(&em28xx_extension_devlist_lock);
+ mutex_lock(&em28xx_devlist_mutex);
if (!list_empty(&em28xx_extension_devlist)) {
list_for_each_entry(ops, &em28xx_extension_devlist, next) {
if (ops->fini)
ops->fini(dev);
}
}
- mutex_unlock(&em28xx_extension_devlist_lock);
+ mutex_unlock(&em28xx_devlist_mutex);
}
diff --git a/drivers/media/video/em28xx/em28xx-dvb.c b/drivers/media/video/em28xx/em28xx-dvb.c
index 8f23aa1..f0de731 100644
--- a/drivers/media/video/em28xx/em28xx-dvb.c
+++ b/drivers/media/video/em28xx/em28xx-dvb.c
@@ -466,6 +466,7 @@ static int dvb_init(struct em28xx *dev)
}
dev->dvb = dvb;
+ mutex_lock(&dev->lock);
em28xx_set_mode(dev, EM28XX_DIGITAL_MODE);
/* init frontend */
switch (dev->model) {
@@ -589,15 +590,16 @@ static int dvb_init(struct em28xx *dev)
if (result < 0)
goto out_free;
- em28xx_set_mode(dev, EM28XX_SUSPEND);
em28xx_info("Successfully loaded em28xx-dvb\n");
- return 0;
+ret:
+ em28xx_set_mode(dev, EM28XX_SUSPEND);
+ mutex_unlock(&dev->lock);
+ return result;
out_free:
- em28xx_set_mode(dev, EM28XX_SUSPEND);
kfree(dvb);
dev->dvb = NULL;
- return result;
+ goto ret;
}
static int dvb_fini(struct em28xx *dev)
--
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