Re: libusb broken on 2.6.28 x86_64 ?

[Mark Lord <lkml@rtr.ca>]

Greg KH wrote:
> On Fri, Jan 02, 2009 at 02:51:13AM -0500, Mark Lord wrote:
>> Greg KH wrote:
>>> On Fri, Jan 02, 2009 at 02:01:21AM -0500, Mark Lord wrote:
>>>> Mark Lord wrote:
>> ..
>>>> Mmm.. broken only for 64-bit userspace, it seems.
>>>>
>>>> I've recompiled the same app against 32-bit libs,
>>>> and it works just fine on that 64-bit system,
>>>> as well as on 32-bit systems.
>>>>
>>>> But not when compiled for pure 64-bit operation on a 64-bit system.
>> ..
>>> Which version of libusb, a new one was just released a few weeks ago
>>> that fixes a lot of problems reported in the older libusb versions, and
>>> made things much faster to boot.  You might want to check it out.
>> ..
>>
>> This is with libusb-0.1-4, which has been working fine with all prior 
>> kernels,
>> including the 2.6.27.xx series.
>>
>> Userspace stuff like this is not supposed to be broken from kernel to 
>> kernel.
> 
> No it shouldn't, I was thinking this was the first time you had tried
> such a thing (64bit userspace apps.)
> 
> If using 2.6.27 works, then we need to fix this.
..

Yup.  I don't really see anything likely in kernel from 2.6.27 to 2.6.28,
other than perhaps the new "poisoning" code.  I wonder if that could be it?

Kinda weird that the device works with libusb the first time it is used,
but then fails on all subsequent runs of the same app, until replugged.

But.. I can run the 32-bit compat app after a 64-bit failure,
and *that* does work.  There's gotta be a useful clue in there somewhere.

Cheers