Re: Updating u-boot for oe-core or meta-yocto

[Darren Hart <dvhart@linux.intel.com>]

On 05/24/2011 11:35 AM, Khem Raj wrote:
> On (24/05/11 11:23), Darren Hart wrote:
>> On 05/24/2011 10:23 AM, Khem Raj wrote:
>>> On (24/05/11 09:36), Darren Hart wrote:
>>>> I've started pulling in the 15 or so patches to u-boot from meta-ti. In
>>>
>>> why ? its a BSP recipe and bsp layer is best place for it IMO unless you
>>> want to have some of those machines in a different layer.
>>
>>
>> The underlying goal here is to improve the Beagleboard support in
>> meta-yocto, without unnecessarily duplicating work. 
> 
> so essentially you are interested in maintaining this board in
> meta-yocto and not use meta-ti as long as you have a process to sync
> your changes in a sane manner between two layers I think it should be
> ok.


Ideally the only beagleboard specific recipe we would be linux-yocto*.
However, if there is objection to updating the oe-core u-boot recipe,
then we'll need to add u-boot to the list.


> However we have to make clear if someone uses both meta-ti and meta-yocto
> and he should be absolutely clear about what recipes and configurations
> he/she ends up picking.


Perhaps ensuring meta-ti layer priority is above that of meta-yocto
would be adequate? Not something I have tried yet.


> 
> It was suggested at
>> ELC that we modify the u-boot and linux-yocto recipes/sources to include
>> the beagleboard specific changes from meta-ti. Once the boot loader and
>> kernel were in place, we would look to using the still-under-discussion
>> layer tooling to integrate the rest of meta-ti.
>>
>>
>>>
>>>> doing so I've come across some questions I'd like you thoughts on.
>>>> Specifically, where to put these changes. Some points of context:
>>>>
>>>> 1) oe-core is intended to support emulated machines only
>>>> 2) oe-core has a "virgin" u-boot recipe (no patches)
>>>> 3) meta-yocto does not have a u-boot recipe (no bbappend either)
>>>> 4) meta-ti has it's own u-boot recipe with per-machine patches
>>>>
>>>> A stated goal was to bring the Yocto Project's u-boot support for the
>>>> Beagleboard in line with that in meta-ti. There are several ways I can
>>>> go about this.
>>>>
>>>> a) create a bbappend in meta-yocto and duplicate the meta-ti
>>>>    modifications in bbappend form.
>>>> b) Modify the oe-core recipe directly
>>>>
>>>> While a) is the most direct approach to accomplish our goal, it requires
>>>> continual maintenance and duplicates effort. I don't care for this
>>>> approach. b) has the potential to consolidate all beagleboard u-boot
>>>> recipe work into a single place. It could simplify the meta-ti and
>>>> eliminate the need for a bbappend in the meta-yocto layer.
>>>>
>>>> The question of whether bootloaders have a place in oe-core should
>>>> probably be addressed. While they aren't needed for the emulated
>>>> machines, they are a highly reusable component for real systems, and
>>>> that seems justify keeping them in oe-core. Does anyone disagree with
>>>> this assessment?
>>>>
>>>> I propose pulling the necessary changes to u-boot from meta-ti into
>>>> oe-core. My initial scan suggested the beagleboard patches are mostly
>>>> contained to beagle specific source files. I would prefer to pull in all
>>>> the patches for all machines into the SRC_URI, rather than divide them
>>>> up by machine. This reduces complexity considerably. For the couple of
>>>> patches that collide, we would keep those as machine specific.
>>>>
>>>> As a final part of the work, I would include my beagleboard patch status
>>>> audit in the included patches and continue to work on reducing the
>>>> patches in the recipe for the beagleboard.
>>>>
>>>> Thoughts?
>>>
>>> Well I am in similar boat where I wanted to build atom-pc for angstrom
>>> but I was thinking using meta-intel layer instead of pulling stuff out
>>> and stuffing it elsewhere and certainly not oe-core
>>
>>
>> I think the difference I'm seeing is that u-boot is a common recipe (it
>> exists in oe-core) and ideally it would track the upstream git
>> repository. If the recipe in oe-core is not intended to be used for any
>> real machines and isn't used as a base for bbappends in layers like
>> meta-ti (meta-ti has a complete uboot_git.bb), then it should just be
>> removed entirely.
> 
> 
> I would agree on removing them from oe-core yes


I guess it comes down to the question of which is our priority:

1) Only including packages in support of emulated targets
2) Providing a common base which multiple layers can build from

I was under the impression that #2 took precedence. Am I wrong here?


>> I believe that there is value in not duplicating this recipe and
>> consolidating the modifications to it in a single place makes sense. The
>> fact that it needs so many non-upstream patches I think is something
>> that also needs to be addressed.
> 
> u-boot and any other bootloader for that matter are machine specific
> and its very hard to have a common recipe serving needs of all machines
> 
> best it could do is abstract out common parts which wont be many in
> u-boot case since it just have many differences so having it in bsp
> layer is probably the best


I confess to being relatively new to u-boot. That said, the current
2011.03 release builds and works on the beagleboard C4 and xM without
modification. The changes I was proposing to pull in are 1/3 upstream
already, some pending, and some not sent upstream yet. Some of these are
purely cosmetic, none are critical for basic functionality.

However, I haven't tried to use it with other boards, if I can't do that
without modifying it in such a way that breaks it for other boards, then
I would agree with you.


> 
>>
>> The second part is that we want to ensure the linux-yocto recipe and
>> kernel have complete support for the Beagleboard. This isn't something
>> we can do by just reusing a layer. The linux-yocto recipe takes a
>> different approach to managing BSP specific source and config changes. I
>> believe it reduces duplication of effort for things like bug fixing,
>> security fixes, and config fragment management.
>>
> 
> but linux-yocto have different recipes. Does it also cover u-boot ?
> in oe-core we would be able to live without linux-yocto having
> beagleboard support since oe-core it should only build qemu
> machines

It does not cover u-boot. In the strictest sense, we do not have
beagleboard support for linux-yocto in oe-core - because the machine is
not defined, so the kernel would never be configured and built for it -
but the bsp layers and meta data are present in the linux-yocto*.git
repository all the same.


-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel