Re: [patches] [PATCH] RISC-V: Support built-in dtb

From: Palmer Dabbelt
Date: Thu Dec 21 2017 - 15:48:12 EST

On Thu, 21 Dec 2017 12:43:20 PST (-0800), Arnd Bergmann wrote:
On Thu, Dec 21, 2017 at 9:32 PM, Palmer Dabbelt <palmer@xxxxxxxxxx> wrote:
On Wed, 20 Dec 2017 01:14:31 PST (-0800), zongbox@xxxxxxxxx wrote:

I've added Arnd and Olof, in case they have a bit more perspective here. If
I'm reading this correctly, there isn't an arm or arm64 option to do this.
There is an option to built in many DTBs, which makes a lot more sense to me
as it doesn't tie the kernel to any one particular implementation. We'd
need a mechanism for picking the DTB that Linux should use. We've kicked
around the idea of:

* Having the bootloader always provide a DTB.
* Taking a hash of that DTB when booting Linux.
* Using that hash to look up DTBs that are built in to Linux.

This would allow us to support replacing broken DTBs if they escape into the
wild, but would still allow us to have a portable kernel.

Having an embedded DTB is only necessary for platforms with a legacy bootloader
that doesn't understand DT at all, you should never need that here.

I would suggest to require each bootloader to provide a way to replace the DTB
with one that gets installed alongside the kernel.

Sounds good to me.