Hi Hans,
Patch works as expected, thanks!
Regards,
Chris
On Tue, Mar 11, 2014 at 10:45 AM, Hans de Goede <hdego...@redhat.com> wrote:
> Hi Chris,
>
>
> On 03/11/2014 05:27 PM, Chris Dickens wrote:
>
>> 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=22763c5cf3690a681551162c15d34d
>> 935308c8d7
>>
>> (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=22763c5cf3690a681551162c15d34d
>> 935308c8d7#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.
>>
>
> Ah yes I see now, and there is a big honking list of compatible ioctls (so
> which are compat without
> needing translation from 32 <-> 64 bit) higher up in the file. Which of
> course does no contain
> the new ioctls. So now we have a different return code when running in
> native 32 bit versus
> when running 32 bits code under a 64 bit kernel how nice (not).
>
> Ok, so treating EINVAL as ENOTTY is going to be the only solution then,
> can you try the
> attached patch?
>
> Thanks & Regards,
>
> Hans
>
>
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