[LinuxBIOS] Hardware best practises for optimal LinuxBIOS ports

[Peter Stuge]

I got an idea today.

We could create a wiki page where we document how LinuxBIOS (porting,
and otherwise) is affected by hardware design decisions.

This could be a very helpful resource for vendors that want to
leverage LinuxBIOS to the fullest in new designs.

Some or most points will have tradeoffs, but the point is to document
them since some decisions that a hardware engineer or even manager or
exec may consider unimportant can actually make a big difference for
the software developers.

Am I being too naive? Maybe it would be old news?


Here are some discussion points to start with. I'll add a page
with content after some feedback. There are many more points, I've
only come up with those that affect LinuxBIOS porting. I imagine a
lot can be learned from OLPC that would go on this page.


* SuperIO serial port rs232 tx/rx on header or pads, or TTL levels,
or EHCI debug port on one of the onboard USB ports.

Pros: Reliable debugging, faster porting
Cons: Board land, BOM cost, less so with only TTL and pads, possibly
more complex routing for the USB debug port


* Avoid or document flash chip write protection

Pros: Less hard/software requirements for porting, faster porting
Cons: Risk of malware or user error bricking board


* Avoid SMM

Pros: Faster porting
Cons: Board land, BOM cost


* Use already supported chips

Pros: Faster, if not instant, porting
Cons: Limited BOM suppliers, may lack state-of-the-art features


* Avoid embedded controllers (for things that concern LinuxBIOS)

Pros: Faster porting
Cons: EC may be required for key features


//Peter