The NextThing's C.H.I.P. can have expansion boards called DIPs. Those DIPs
are connected through the external headers, and comes with an
identification mechanism based on 1-Wire EEPROMs.
That auto-detection works great, because 1-Wire allows the enumeration, and
the EEPROMs are guaranteed to have different addresses, which allows us to
stack as many DIPs as possible, without any constraints.
Since those DIPs can be close to anything, ranging from a simple PWM-based
buzzer to a full featured device such as the PocketCHIP (which comes with a
touchscreen, a keyboard, a battery, etc), some adjustments might be needed
in U-Boot to be able to present something that just works to the user.
In particular, we need to:
- Apply an overlay if the device is something that should be dealt with
early in the boot process (display, storage device)
- Adjust the U-Boot environment if the DIP has a display to change the
default video output
- Adjust the kernel command line in previous case for Linux to have the
same default
In order to achieve that, we introduced some logic optionally hooked into
the sunxi board, two new uclasses for 1-Wire and EEPROMs, and a bunch of
new environment variables:
- dip-auto-video to control the automatic video set up (default to yes)
- dip_overlay_cmd that is a script to load the overlay $dip_overlay_name
to $dip_addr_r, from whatever place it was stored in, and later apply
it.
- kernelarg_video to host the default kernel output in the kernel
command line
I think the biggest drawback at the moment is that we maintain a list of
DIPs and the actions needed directly into the C code, which will make it
quite hard to customise for end users and tedious to maintain in the long
term. I couldn't really get my head around a better solution, so feel free
to suggest alternative approaches.
Let me know what you think,
Maxime
Maxime Ripard (9):
fdtdec: Fix alias retrieval
sunxi: chip: Add 1-wire node
w1: Add 1-Wire uclass
w1: Add 1-Wire gpio driver
EEPROM: Add an EEPROM uclass
eeprom: Add DS2431 support
video: Allow board hook before video init
sunxi: Add CHIP's DIP support
config: chip: Enable DIP support
arch/arm/dts/sun5i-r8-chip.dts | 15 ++-
board/sunxi/Kconfig | 9 +-
board/sunxi/Makefile | 1 +-
board/sunxi/board.c | 6 +-
board/sunxi/dip.c | 227 ++++++++++++++++++++++++++++++-
configs/CHIP_defconfig | 5 +-
drivers/Kconfig | 4 +-
drivers/Makefile | 2 +-
drivers/eeprom/Kconfig | 23 +++-
drivers/eeprom/Makefile | 3 +-
drivers/eeprom/ds2431.c | 38 +++++-
drivers/eeprom/eeprom-uclass.c | 57 +++++++-
drivers/video/cfb_console.c | 9 +-
drivers/w1/Kconfig | 23 +++-
drivers/w1/Makefile | 3 +-
drivers/w1/w1-gpio.c | 160 +++++++++++++++++++++-
drivers/w1/w1-uclass.c | 259 ++++++++++++++++++++++++++++++++++-
include/dm/uclass-id.h | 2 +-
include/eeprom.h | 21 +++-
include/w1.h | 47 ++++++-
lib/fdtdec.c | 3 +-
21 files changed, 916 insertions(+), 1 deletion(-)
create mode 100644 board/sunxi/dip.c
create mode 100644 drivers/eeprom/Kconfig
create mode 100644 drivers/eeprom/Makefile
create mode 100644 drivers/eeprom/ds2431.c
create mode 100644 drivers/eeprom/eeprom-uclass.c
create mode 100644 drivers/w1/Kconfig
create mode 100644 drivers/w1/Makefile
create mode 100644 drivers/w1/w1-gpio.c
create mode 100644 drivers/w1/w1-uclass.c
create mode 100644 include/eeprom.h
create mode 100644 include/w1.h
base-commit: d8bdfc80da39211d95f10d24e79f2e867305f71b
--
git-series 0.8.11
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