Messages in this thread | | | From | "Albert D. Cahalan" <> | Subject | Re: temperature standard - global config option? | Date | Sat, 9 Jun 2001 04:00:44 -0400 (EDT) |
| |
Michael H. Warfiel writes: > On Fri, Jun 08, 2001 at 05:16:39PM -0400, Albert D. Cahalan wrote:
>> The bits are free; the API is hard to change. >> Sensors might get better, at least on high-end systems. >> Rounding gives a constant 0.15 degree error. >> Only the truly stupid would assume accuracy from decimal places. >> Again, the bits are free; the API is hard to change. ... > No... The average person, NO, the vast majority of people, > DO assume accuracy from decimal places and honestly do not know the > difference between precision and accuracy. I've had comments on this > thread in private E-Mail the reinforce this impression.
I hope you don't think people would assume that a "float" always has useful data in all 23 fraction bits. It is a similar case.
So here you go, a kernel-safe conversion from C to K. It works from 0 to 238 degrees C. Print as hex, so user code can toss it into a union or maybe abuse scanf. Adjust as needed for F to K or for hardware with greater resolution.
/* unsigned int degrees C --> float degrees K */ unsigned ic_to_fk(unsigned c){ unsigned exponent; unsigned tmp;
tmp = (c<<23) + 0x88933333; /* Kelvin shifted 23 left */ exponent = 127; /* IEEE floating-point bias */ while(tmp&0xff000000){ tmp >>= 1; exponent++; } tmp &= 0x007fffff; /* keep only the fraction */ tmp |= exponent<<23; return tmp; } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |