tools: usb: usbip: adding support for older kernel versions

[Shuah Khan <shuah@kernel.org>]

On 3/25/19 5:02 PM, Brian Norris wrote:
> On Mon, Mar 25, 2019 at 3:07 PM shuah <shuah@kernel.org> wrote:
>> On 3/25/19 11:56 AM, Brian Norris wrote:
>>> On Mon, Mar 25, 2019 at 8:51 AM shuah <shuah@kernel.org> wrote:
>>>> In general the ABI is stable.
>>>
>>> No, it really isn't. This commit was a breaking change:
> ...
>>> But this one is definitely a break:
>>>
>>> commit 1c9de5bf428612458427943b724bea51abde520a
>>> Author: Yuyang Du <yuyang.du@intel.com>
>>> Date: Thu Jun 8 13:04:10 2017 +0800
>>>
>>>     usbip: vhci-hcd: Add USB3 SuperSpeed support
>>>
>>> You can't just arbitrarily add columns to the beginning of a file like
>>> that and claim that you're not breaking ABI. And I shouldn't need to
>>> remind you that Thou Shalt Not Break User Space.
>>
>> USB 3.0 driver and tool support went in, I would say it was oversight to
>> not make sure the tool continues to work on older kernels.
> 
> While that's true, you're still not grokking my main point when asking
> about ABI stability:
> 
>    *old* tools should still work on *new* kernels
> 
> The above commit broke that.
> 

Agreed. Let's move forward with the assumption that this won't happen
in the future.

On a side note, in this specific tool case, the newer version is more
secure than the older version.

thanks,
-- Shuah