On Wed, Nov 20, 2013 at 07:25:09PM +0100, Jean Delvare wrote: > On Wed, 20 Nov 2013 10:15:29 -0800, Guenter Roeck wrote: > > On Wed, Nov 20, 2013 at 07:06:41PM +0100, Jean Delvare wrote: > > > Personally I'd just do the minimum to avoid returning an error. In > > > other words I'd be fine returning values down to 6 degrees (for the > > > Atom D510 at least). We know the value is wrong but it can be corrected > > > in user-space, while if we clamp higher, it can no longer be corrected. > > > > Seems to me it would be much simpler to just return 0 if the valid bit is 0, > > and not bother returning -EAGAIN in that case. After all, that is what > > it boils down to, isn't it ? > > In the specific case of these Atom chips, sort of, yes (although I'd > return maybe 5000 for continuity with the last known good value, but > that's not so important in the end, plus there's no guarantee that the > limit is the same for other Atom CPU models / samples.) > > However we can't really do that in general, as again there is no Intel > documentation saying that valid == 0 can only mean "temperature too > low". There may be other causes. > > Now I really can't remember if we ever had reports of -EAGAIN being > returned transiently. If the error is always permanent then I'd agree > that returning 0 (or any other arbitrarily low value) is no worse than > returning -EAGAIN. > > Alternatively, as long as we have no clean way to return "lower than X > but I don't know the exact value" to user-space, it might be more > simple to just ignore the valid bit and always return the value. In > ticket #2382 I found that values 1°C and 4°C would be returned instead > of the error in that case, it's no worse than returning 0°C or an > arbitrary 5°C, and it would come for absolutely no extra code. > Both are ok with me. Either case it would be a one-line change. - return tdata->valid ? sprintf(buf, "%d\n", tdata->temp) : -EAGAIN; + return sprintf(buf, "%d\n", tdata->valid ? tdata->temp : 0); or - return tdata->valid ? sprintf(buf, "%d\n", tdata->temp) : -EAGAIN; + return sprintf(buf, "%d\n", tdata->temp); Let me know which one you prefer and I'll submit a patch. Thanks, Guenter _______________________________________________ lm-sensors mailing list lm-sensors@xxxxxxxxxxxxxx http://lists.lm-sensors.org/mailman/listinfo/lm-sensors
