Re: Kernel specific branches question

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Hi Johannes,
>Hi Dan,

>> At Laird, we use backports for supporting our wireless modules,
>> specifically using an unmodified brcmfmac, a fairly modified ath6kl,
>> and an out of tree custom version of the non-upstreamed mwlwifi, and
>> also using unmodified Bluetooth.  


>> At the moment, we are backporting our fork of the 4.9 kernel for
>> those drivers.  I pulled a copy of the git repo a few months back and
>> we have worked from that.  I’m wondering how we can help resurrect
>> the process of having branches for specific kernel releases and the
>> testing that was done for those as seen in this commit:
>> it/commit/?h=linux-4.4.y&id=bec4037a54dd0e1a1aeefe7385faf82bac44d6a0

>So the testing thing there is just the output from the "ckmake" script
>that's there in the repository. It needs a bunch of disk space and lots
>of CPU time, but otherwise shouldn't be that hard to do. We still have
>the compat build box, and I still have a plan to put some kind of
>automation in place, but haven't really had time for it yet.

This is great information, we will probably attempt to set this up
internally for our QA testing.

>However, this is pretty different from how most other people seem to

>Since kernel releases are sort of ephemeral, and drivers are
>continually developed along with the kernel, we typically see usage
>more of "latest backport + latest kernel" to get to "latest driver for
>use on any kernel".

I think only wireless module vendors would have our use case.  Just to 
elaborate a bit more.  We sell several system on modules
with 802.11 and bluetooth combo modules. We also sell the wireless
combo modules separately in a variety of form factors for integrating 
into other systems. We jump the kernels on those SOMs to the latest LTS 
kernel when released.  We do all our wireless module bring up, debugging, 
baseline, and QA testing of those wireless modules using LTS kernels
using our SOMs.  To support software releases for those wireless only modules
we use backports on those SOMs kernel to release a driver that builds for 
many different kernels and rely on the QA testing that pertains to 
the wireless module on the SOM.  This backports tarball is released with
the firmware and the wpa_supplicant that was used during this
QA process.  If a specific major release works well for the customer, they 
may stay on this release and only want a bug fix or two.  
We continually move forward with new releases but maintain those older
releases for customers if required.

>Additionally, backports for a fixed kernel version like 4.9 really
>should be pretty stable, so once you have it, it shouldn't really need
>to change? So it seems to me like a tag on master would be sufficient.

I agree this really is all we would need.

>Now, we're not actually doing a good job of following any of upstream,
>linux-next or wireless-testing with backports right now - we should
>probably pick one of those, or multiple of those, and create branches
>in the backports.git for each one of those, rather than having a
>"master" branch.

My preference would be linux-next, but it would be interesting to have both.

>To do that, I think we should actually set up a build bot to do a daily
>tests of applying backports on those trees, and then compiling the
>result on all (supported) kernels. This can then email the list, and
>somebody can fix the issues.

>Sounds like a plan?

This sounds fantastic and would enable us to help keep the project up
to date :).

>Note that I'm going to go no sabbatical for July/August, so I won't be
>working on this then either though.

Gives us time to see if we can get the cmake script set up ourselves as well.

Thanks for the reply.  Looking forward to helping out!


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