Hi Mario,
On 22 February 2017 at 08:07, Mario Six mario.six@gdsys.cc wrote:
Certain boards come in different variations by way of utilizing daughter boards, for example. These boards might contain additional chips, which are added to the main board's busses, e.g. I2C.
The device tree support for such boards would either, quite naturally, employ the overlay mechanism to add such chips to the tree, or would use one large default device tree, and delete the devices that are actually not present.
Regardless of approach, even on the U-Boot level, a modification of the device tree is a prerequisite to have such modular families of boards supported properly.
Therefore, we add an option to make the U-Boot device tree (the actual copy later used by the driver model) writeable, and add a callback method that allows boards to modify the device tree at an early stage, at which, hopefully, also the application of device tree overlays will be possible.
Signed-off-by: Mario Six mario.six@gdsys.cc
Changes in v3:
None
Changes in v2:
- Switched from usage of globally writeable global data pointer to a locally writeable pointer passed to board_fix_fdt
- Added comments for board_fix_fdt in include/common.h
- Added documentation for pre-relocation device tree manipulation
common/board_f.c | 10 ++++ doc/driver-model/fdt-fixup.txt | 132 +++++++++++++++++++++++++++++++++++++++++ dts/Kconfig | 10 ++++ include/common.h | 1 + 4 files changed, 153 insertions(+) create mode 100644 doc/driver-model/fdt-fixup.txt
Reviewed-by: Simon Glass sjg@chromium.org
I think as things stand this is reasonable.
But IMO it would be better (i.e. faster) to manipulate the live DT, assuming we have one (see my series on that).
Regards, Simon