Re: [PATCH v3 1/3] xen/ns16550: Make ns16550 driver usable on ARM with HAS_PCI enabled.

[Julien Grall <julien@xxxxxxx>]

Hi Jan,

On 24/11/2020 09:47, Jan Beulich wrote:
> On 23.11.2020 18:13, Julien Grall wrote:
> > My view on 2) can change if Jan provides enough information into why one
> > would want NS1650 PCI enabled by default on Arm but disable MSI.
> Because, like it was on x86, initially there may be no support for
> MSI?
"no support for MSI" implies that there will be at least support for 
NS16550 PCI.
>  I have no idea what the plans are ...
There are no such plan on Arm for the forseeable future (read as we 
haven't seen any interested from the Arm community).
The NS16550 PCI code will stay unusable until someone effectively send a 
patch to plumb it correctly.
While I agree that disabling MSI may be nice to have to do in the 
future, this doesn't address the need for Arm. I don't want to get in 
our way the NS16550 PCI code in our way when implementing PCI (with or 
without MSI) on Arm.
Even if there were an interest, I would still expect some users (e.g. 
embedded folks) to want to compile-out unused feature (you may have a 
platform with a embedded NS16550).
So the path forward will stay either 1) or 3) for me.

Cheers,

--
Julien Grall