IEEE-754 Float to int
tanure at linux.com
Wed Nov 23 07:30:09 EST 2016
On Tue, Nov 22, 2016 at 4:55 PM, Greg KH <greg at kroah.com> wrote:
> On Tue, Nov 22, 2016 at 04:44:43PM +0000, Lucas Tanure wrote:
>> On Tue, Nov 22, 2016 at 4:39 PM, Greg KH <greg at kroah.com> wrote:
>> On Tue, Nov 22, 2016 at 04:05:18PM +0000, Lucas Tanure wrote:
>> > Hi,
>> > At some point my hardware gives me a 32bit IEEE-754 float, like this :
>> > regmap_read(device->regmap, ADDR0, &temp);
>> > value = temp << 16;
>> > regmap_read(device->regmap, ADDR1, &temp);
>> > value |= temp;
>> > So, value has a 32bit float now, and I would like to print just the
>> > part, like :
>> > Read 26.92387 --> Print 26.
>> > Simple, no float operations.
>> > How I can do it ?
>> Just print the upper 16 bits shifted right by 16 bits.
>> But why would you want to print the value anyway? Who would use it?
>> My hardware gives me the board temperature as a float 32bits.
>> And the hwmon sysfs api asks me to return the temperature as millidegree
>> To follow the hwmon sysfs api rules, I need to get my float, multiply by 1000
>> and print the integer part.
>> There is a better way to do that ?
> Ah, yeah, sorry, my example is wrong. There's got to be other drivers
> that also do this same thing, try asking on the hwmon mailing list, they
> should know how to do this best, as they are the ones responsible for
> that user/kernel api.
> greg k-h
For future reference:
The best way to do it seems to be to write conversion function.
Receive the float in a u32, parse it's bits and return a s32. Can be
done without the use of floats.
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