On Fri, 7 Dec 2001, Young Joon Lee wrote:
> Hi,
>
> I tried to print 3.14159 in rtl_printf.
> But %f, %lf, %e are not working in rtl_printf().
> Does anybody know how to do this?
:). You can't. For some reason the philosophy of the kernel was that you
can't/shouldn't do anything with floats in the kernel (I think maybe it
has to do with keeping context switches more efficient?). As such, the
%g/%f conversion specifiers are unimplemented in printk and rtl_printf.
However, there is hope: I believe I remember seeing a bunch of patches
floating (no pun intended) around that can modify rtl_printf to handle
floats/doubles. Also, it probably wouldn't be that hard to roll your own,
as it were, and implement the feature yourself for your own personal use..
if all else fails.. :/
Here would be a simple and crude way to print a float using only %d as a
primitive.. it's crude but works in a pinch for debugging code:
void
print_a_double (double d)
{
int left = d, right = (d - left) * 1000; /* change this 1000 for
more or less
precision */
/* uncommend the below 'rtl_' if in rtlinux task */
/*rtl_*/printf ("%d.%d", left, right);
}
-Calin
>
>
>
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