On 08/31/2015 08:33 AM, Johannes Berg wrote:
> On Mon, 2015-08-31 at 08:21 -0500, Pierre-Louis Bossart wrote:
>>>
>>> The *to* version is never relevant. A given backport will compile
>>> against many different *to* versions.
>>
>> I guess I completely missed the concept. I was thinking that the 
>> gentree.py command would only port and adjust the delta between linux
>> -next and the version I wanted. Looks like the backport is really an 
>> add-on that will apply to multiple versions. Not sure I understand 
>> how successive changes in the tree are handled if there is a single 
>> backport.
> 
> Well, there's a single *from* version, as you say that was currently
> "next-20150731" (or that was the one you used). The backport git
> repository is maintained in lockstep with the *from* version (although
> there's usually quite a bit of wiggle room)
> 
> The result, the output of backports, will/should compile against any
> kernel starting from the earliest supported, all the way up to the
> *from* version, right now I think that's 3.0 until 4.1 or so. 

What I was really looking for is the --integrate option that does merge the backport into an existing tree.
This option is broken btw on newer kernels due to a change in the kernel Makefile in October 2014, the attached patch provides a correction (not sure how to use the right patch for the right kernel though).
-Pierre