[meta-xilinx] ZC702 support in Xilinx meta-xilinx

[Sipke Vriend]

Hi Mike,

You may well have something that we have overlooked, so I've got some 
questions below to try to further understand.

On Wednesday, 24 April 2013 4:11 PM, Mike Looijmans wrote
>
>> Yes it is our intention at this point to have a layer per board. I think
>> there is an advantage in layering because it will help distinguish between
>> architecture and bsp (i.e. Zynq and Microblaze vs Board/BSP 'configuration')
>
>What would be the advantage of having a BSP per board?
>

The multiple board/bsp layers just extract any board info (and this is minimal) 
into a separate layer. For users, the advantages I guess are primarily for us as
 a vendor and new users, not so much for advanced users. Advanced users are 
likely to ignore these bspboard layers and create their own on top of the 
architecture layers. New users though have a starting point by having a 
minimalistic board layer to start investigating.

>I can mostly only find disadvantages. Many of the OpenEmbedded projects 
>I work with are designed to build on multiple targets. Usually a single 
>environment builds two or three different machines, and often this 
>number increases when there are newer (or prototype) versions of 
>products. One project now builds for 22 machine configurations.
>

Are you saying that having multiple 'thin template bsp/board layers' would 
hinder these multi-machine targeted projects?
If so, this is significant and we need to understand it so we can allow
for such builds. Some information as to how the builds actually happen, 
like are there multiple build folders each with local.conf and bblayers 
files etc would help in understanding the process.

>I can see a case for a "microblaze" and a "zynq" layer, but I really 
>don't see the advantage of having a zc702, zedboard, and various other 
>separate layers that must be versioned and managed separately.
>

Understood and we have considered having separate microblaze and zynq 
layers. Currently this is achieved through tune includes only. 
We are in development and appreciate these kind of comments a lot.

>A EVM is usually a starting point for a project. It usually evolves from 
>there, first just adding hardware to the board, and later with product 
>prototypes based on similar hardware. 

Agreed that the EVMs are starting points, and our 'template bsp/board 
layers' are targeting those starting points, particularly for new users.
Let's call them 'EVM layers', to help clarify their purpose.

>When problems arise, we usually 
>evaluate if the other board showed the same symptoms, so we can find out 
>whether it's the hardware or software to blame. That makes it very 
>important to always have access to multiple machines. If we need to add 
>or switch layers to be able to target other machines, we can no longer 
>be sure that we are using the same software on both, and we would have 
>to thoroughly investigate the changes that each layer brings.
>

As asked above, I think I need a bit of enlightenment in how the 
multiple machine targeting actually happens. Examples of existing OE 
machines targeted, as a comparison, would help also.

>I hope these stories help you gain some perspective on how OE is being 
>used in the wild.
>

Very much so, and thanks!
Regards,
Sipke