Hi Hans,
Are you sure this is what was happening ? Can you perhaps try again with
> a printf added at a strategic place to ensure this is really what is going
> on?
>
Here's the debug output right after the DISCONNECT_CLAIM fails:
[ 0.004913] [00007d79] libusb: debug [libusb_claim_interface] interface 1
[ 0.004930] [00007d79] libusb: debug [detach_kernel_driver_and_claim] ioctl
DISCONNECT_CLAIM error -1 errno 22
Looking at:
>
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/usb/core/devio.c?id=22763c5cf3690a681551162c15d34d935308c8d7
>
> (22763c5c is the commit id responding to the v2.6.32 tag)
>
> I see the following in there:
>
> static int usbdev_ioctl(struct inode *inode, struct file *file,
> unsigned int cmd, unsigned long arg)
> {
> struct dev_state *ps = file->private_data;
> struct usb_device *dev = ps->dev;
> void __user *p = (void __user *)arg;
> int ret = -ENOTTY;
> ...
> switch (cmd) {
> case USBDEVFS_CONTROL:
> ...
> }
> return ret;
> }
>
> This code path is used for calls from both 64 bit and 32 bit userspace
> apps,
> so 32 bit apps should see -ENOTTY to for an unknown cmd code.
The code for RHEL's 2.6.32 kernel is a bit different, but essentially boils
down to the same thing. (I was referencing
http://ftp.redhat.com/redhat/linux/enterprise/6Workstation/en/os/SRPMS/kernel-2.6.32-431.5.1.el6.src.rpm
)
Doing a bit more research, I've found this is actually happening further up
the call stack, before usbfs is ever involved. I noticed this in the kernel
log:
ioctl32(pcs:32121): Unknown cmd fd(11) cmd(8108551b){t:'U';sz:264}
arg(f59b4c50) on /dev/bus/usb/001/079
This message is generating from
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/compat_ioctl.c?id=22763c5cf3690a681551162c15d34d935308c8d7#n2769
This is called from inside the compat_sys_ioctl function (
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/fs/compat_ioctl.c?id=22763c5cf3690a681551162c15d34d935308c8d7#n2857)
and is called when the file operations table does not provide a
compat_ioctl function and no handler is found. usbfs indeed does not
provide this, thus after failing to find a handler it prints this error and
as you can see right after returns EINVAL.
Regards,
Chris
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