[PATCH 1/6] kernel: import dt-overlay configfs patches for 5.10

Oskari Lemmelä oskari at lemmela.net
Sat Nov 27 04:24:52 PST 2021


On 27.11.2021 13.55, Daniel Golle wrote:
> On Sat, Nov 27, 2021 at 11:28:05AM +0200, Oskari Lemmelä wrote:
>> Hi,
>> On 25.11.2021 3.06, Daniel Golle wrote:
>>> Import patchset allowing loading and applying device tree overlays at
>>> run-time via configfs.
>>> This will allow for packaging DTOs for hardware add-ons such as the
>>> various HATs (Hardware Attached on Top) common for SBCs.
>>> A new kernel config option CONFIG_OF_CONFIGFS is introduced and some
>>> additional sysfs attributes are added in case CONFIG_OF_OVERLAY is
>>> enabled.
>> Is this something that did not get accepted by upstream linux?
>> Those patches seem to be almost 8 years old.
> I didn't investigate the full history of that patchset, I just found
> it to be the default and only way available to modify DT from
> user-space (and hence useful for SBC targets).

If I remember correctly dynamic runtime DT loading was rejected by linux
community. Many SBC distros used them, but when it did not make to
mainline they have changed strategy.

U-boot dynamic device tree loading have been implemented after that to
do same thing before Linux kernel is loaded.


> Quite a few trees on git.kernel.org come with that patch on top and
> when looking for DT overlay documentation, the docs assume you got that
> patch applied [1], [2]...
> [1]: https://elinux.org/R-Car/DT-Overlays
> [2]: https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/guides/dt-overlays.md.html#3-load-overlays-dynamically

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