On 04/01/2013 03:00 PM, Stephen Warren wrote: > On 04/01/2013 03:08 PM, David Collins wrote: >> 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: > > Doesn't the very latest dtc, which contains integer expression support, > allow unary -? I thought that code had been imported into the kernel > (goes and checks) yes it has. What's the error you're seeing; > over/underflow or syntax? > > That said, DT cells are supposed to be u32 not s32, so perhaps this > isn't unexpected. It is likely that my dtc version is out of date. dtc -v outputs 1.2.0. I will try updating to a newer version of dtc. The error that I currently get is a syntax error: "FATAL ERROR: Unable to parse input tree". Does the device tree binary documentation define any format for negative numbers? Unsigned 32-bit integers are clearly defined as bytes in big-endian order. I suppose that you could assume 32-bit signed integers are 2's complement with bytes in big-endian order, but that would need to be well defined somewhere. Assuming that dtb has no well defined means of holding a negative integer value, then what is the most elegant workaround to specify a negative value? -- 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
