Hi DT experts,
I have a question about "simple-mfd".
Documentation/devicetree/bindings/mfd/mfd.txt says as allows:
----------------------8<---------------------
Optional properties:
- compatible : "simple-mfd" - this signifies that the operating system should
consider all subnodes of the MFD device as separate devices akin to how
"simple-bus" indicates when to see subnodes as children for a simple
memory-mapped bus. <snip>
----------------------8<---------------------
I'd like to be sure about the statement above.
Does this mean, "simple-bus" and "simple-mfd" are technically interchangeable?
If so, I thought the example some lines below is questionable.
---------------------8<---------------------------
Example:
foo@1000 {
compatible = "syscon", "simple-mfd";
reg = <0x01000 0x1000>;
led@08.0 {
compatible = "register-bit-led";
offset = <0x08>;
mask = <0x01>;
label = "myled";
default-state = "on";
};
};
---------------------8<---------------------------
Because "simple-bus" indicates that child nodes are
simply memory mapped, but the node "register-bit-led"
can not be memory-mapped.
So, "simple-mfd" can not be replaced "simple-bus" here.
arch/arm/boot/dts/arm-realview-pb1176.dts is a real example.
If I replace "simple-mfd" with "simple-bus",
DTC warns "empty reg/ranges property".
$ sed -i -e 's/simple-mfd/simple-bus/'
arch/arm/boot/dts/arm-realview-pb1176.dts
$ make -s ARCH=arm defconfig
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- W=1 arm-realview-pb1176.dtb
...
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.0 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.1 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.2 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.3 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.4 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.5 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.6 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/led@08.7 missing or empty reg/ranges
property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/osc0@0c missing or empty reg/ranges property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/osc1@10 missing or empty reg/ranges property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/osc2@14 missing or empty reg/ranges property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/osc3@18 missing or empty reg/ranges property
arch/arm/boot/dts/arm-realview-pb1176.dtb: Warning (simple_bus_reg):
Node /soc/syscon@10000000/osc4@1c missing or empty reg/ranges property
--
Best Regards
Masahiro Yamada
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