The following sequence of commands was triggering a kernel crash in
cdev_get():
modprobe cx231xx
rmmod cx231xx
modprobe cx231xx
v4l2grab -n 1
The problem was that cx231xx_usb_disconnect() was not doing anything
because the test:
if (!dev->udev)
return;
was reached (i.e, dev->udev was NULL).
This is due to the fact that the 'dev' pointer placed as intfdata into
the usb_interface structure had the wrong value, because
cx231xx_probe() was doing the usb_set_intfdata() on the wrong
usb_interface structure. For some reason, cx231xx_probe() was doing
the following:
static int cx231xx_usb_probe(struct usb_interface *interface,
const struct usb_device_id *id)
{
struct usb_interface *lif = NULL;
[...]
/* store the current interface */
lif = interface;
[...]
/* store the interface 0 back */
lif = udev->actconfig->interface[0];
[...]
usb_set_intfdata(lif, dev);
[...]
retval = v4l2_device_register(&interface->dev, &dev->v4l2_dev);
[...]
}
So, the usb_set_intfdata() was done on udev->actconfig->interface[0]
and not on the 'interface' passed as argument to the ->probe() and
->disconnect() hooks. Later on, v4l2_device_register() was
initializing the intfdata of the correct usb_interface structure as a
pointer to the v4l2_device structure.
Upon unregistration, the ->disconnect() hook was getting the intfdata
of the usb_interface passed as argument... and casted it to a 'struct
cx231xx *' while it was in fact a 'struct v4l2_device *'.
The correct fix seems to just be to set the intfdata on the proper
interface from the beginning. Now, loading/unloading/reloading the
driver allows to use the device properly.
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxxxxxxxxx>
---
drivers/media/video/cx231xx/cx231xx-cards.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/media/video/cx231xx/cx231xx-cards.c b/drivers/media/video/cx231xx/cx231xx-cards.c
index 53dae2a..bfcc8ab 100644
--- a/drivers/media/video/cx231xx/cx231xx-cards.c
+++ b/drivers/media/video/cx231xx/cx231xx-cards.c
@@ -1135,7 +1135,7 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
cx231xx_info("registering interface %d\n", ifnum);
/* save our data pointer in this interface device */
- usb_set_intfdata(lif, dev);
+ usb_set_intfdata(interface, dev);
/*
* AV device initialization - only done at the last interface
@@ -1157,7 +1157,7 @@ static int cx231xx_usb_probe(struct usb_interface *interface,
v4l2_device_unregister(&dev->v4l2_dev);
kfree(dev);
dev = NULL;
- usb_set_intfdata(lif, NULL);
+ usb_set_intfdata(interface, NULL);
return retval;
}
--
1.7.4.1
--
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