Hi,
I am working on a thermal driver which needs to be able to read a
temperature threshold from a device tree property. The hardware supports
thresholds in the range -204.8 to +204.7 C in 0.1 C steps. I have found,
as I am sure others have as well, that dtc treats a '-' before an integer
in a dtsi file as a syntax error. Therefore, I need some artificial way
to represent negative numbers in device tree. Here are the possibilities
that I have thought of so far:
1. Use a second integer to specify the sign of the threshold:
20000 mC --> <0 20000>
-20000 mC --> <1 20000>
2. Use a string instead of an integer to specify the threshold and
then convert it to an integer in the driver software:
20000 mC --> "20000"
-20000 mC --> "-20000"
3. Use units of millikelvin instead of millicelcius. 0 mC == 273150 mK
20000 mC --> <293150>
-20000 mC --> <253150>
4. Use an arbitrary offset e.g. 0 mC == 1000000
20000 mC --> <1020000>
-20000 mC --> <980000>
5. Use the unsigned 32-bit representation for 2’s-compliment
signed 32-bit integer
20000 mC --> <20000>
-20000 mC --> <0xffffb1e0> or <4294947296>
Which of these options would you recommend using? Is there any better way
to handle negative values that I haven’t listed? What is the best general
case solution for specifying negative numbers in device tree?
Thanks,
David
--
The Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation
--
To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
