[yocto] linux-yocto and private topic branches

[Marc Ferland]

Bruce Ashfield <bruce.ashfield at windriver.com> writes:

> On 12-08-17 04:21 PM, Marc Ferland wrote:
>> Hi,
>>
>> I'm maintaining a BSP based on crownbay and I would like to change my
>> current kernel recipe from a custom one to linux-yocto_3.2.bb.
>
> I'm just heading out for the weekend, but I can pick this up in more
> detail layer.

That would be great!
>>
>> Reading the kernel-yocto.bbclass, I see that it is possible to provide a
>> list of patches and configuration fragments but also (not sure about
>> that) to provide an "external branch".
>
> In the denzil (3.2 kernel) that is the case, in the yocto 1.3 (3.4)
> kernel, it isn't even called an external branch, since the tools
> are more tolerant of a branch not being present at validation time.

BTW, I am using denzil.
>
>>
>> Since we maintain several private topic branches in-house this would be
>> the perfect solution. I could "inherit" from crownbay (available on
>> linux-yocto) and just merge my topic branches to produce the final
>> kernel source tree.
>>
>> My question:
>> Is this currently possible? If so, are there any examples available?
>
> You can do this, but you do need to host your own kernel repository
> that is based off linux-yocto. In that repository, you can have
> your own branches, that are easily referenced from the recipes.
>
> Is this what you are currently doing with your custom recipe ?

We indeed host our own kernel repo but it is based off kernel.org. The
recipe just defines the SRC_URI of that repo along with a defconfig.

So first step for us is to rebase our stuff on linux-yocto!
>
> I'm stating the obvious, since if you want to clone a tree with your
> branch .. there must be a tree somewhere with that branch :)
>
> The yocto-bsp tools are using the external branches to manage new
> BSPs that aren't already in linux-yocto.
>
> There are other tricks that can be played where smaller, pruned git
> trees are used, and they are cloned and have their alternates pointed
> at the main kernel tree repository, gluing the two together. But there's
> nothing within the current models that supports it directly (you need
> reference clones, scripts, etc).
>
>> Can these changes be kept in "recipe-space"?
>
> Most everything that can be done in a tree, with branches and meta data
> can also happen in recipe space. The yocto-bsp scripts are again a
> good example of this.

Ok. I'll definitively have a look at these yocto-bsp scripts. Keeping
everything in recipe space will be easier since all changes will be
concentrated in one place.

Thanks for all the info!

Marc