Re: [RFC PATCH 3/3] arm64: dts: bcmbca: update bcm4808 board dts file

On 2022-07-13 13:09, Krzysztof Kozlowski wrote:

On 13/07/2022 12:55, Rafał Miłecki wrote:

quoted

On 2022-07-12 17:36, Florian Fainelli wrote:

quoted

On 7/12/22 00:47, Krzysztof Kozlowski wrote:

quoted

On 12/07/2022 04:11, William Zhang wrote:

quoted

Update compatible string based on the new bcmbca binding rule
for BCM4908 famliy based boards

Typo - family

Please explain why breaking the ABI (and users of these DTS_ is
acceptable.

This will be largely targeted towards Rafal who supports these kinds
of devices with an upstream kernel. My understanding is that this is
OK because we will always ship a DTB matching the Linux kernel, and I
believe this is true for both the way that William and his group
support these devices, as well as how OpenWrt, buildroot or other
build systems envision to support these devices.

Rafal, does that sound about right?

Right - in all cases I'm aware of - Linux gets shipped with DTB files.
So such change won't actually break anything in real world.

We don't really talk here about Linux, but other projects, like
bootloaders or *BSD...

Right, let me more specific.

BCM4908 uses pkgtb firmware images. Those images contain:
1. bootfs (atf, u-boot, kernel, DTB files)
2. rootfs (filesystem)

So when you flash BCM4908 firmware it always contains:
1. U-Boot and DTB for it
2. Kernel and DTB for it
(+ more stuff)

There isn't any on-flash DTB file that doesn't get updated when flashing
a new image.