linuxkpi: Add `int_sqrt()`

[dumbbell]

Summary

The implementation comes from isqrt64() in sys/cam/cam_iosched.c. It is modified to take an unsigned long and return an unsigned int.

The i915 DRM driver started to use it in Linux 6.15.

Sponsored by: The FreeBSD Foundation

[bz]

sys/compat/linuxkpi/common/include/linux/math.h

67

I believe int_sqrt returns an unsigned long in Linux.

sys/compat/linuxkpi/common/src/linux_math.c

10

Based on? instead of copied as it's not a 1:1 copy thought it may become if we do return the unsigned long? Otherwise also credit @imp in the (c)?

Also do you want to fix style for LinuxKPI?

[dumbbell]

Based on the feedback from @bz:

• Fix return type, it should have been unsigned long.
• Improve comment to explain the source of the code.

[bz]

sys/compat/linuxkpi/common/src/linux_math.c

15

This is not common style for FreeBSD. Usually we take the license/copyright from the file and then keep it at the top.
However, if we expect more functions in this file one day then I actually like this idea (which will give a lot of tools sieving for copyright and licenses a headache) to mark just that part of the code.
However I have no clue if that actually makes a difference.

@imp this is your code and you know all the other bits related to this.

[dumbbell]

Address concern from @bz

sys/compat/linuxkpi/common/src/linux_math.c

15

I moved the copyright at the top like in all other places.

[bz]

sys/compat/linuxkpi/common/src/linux_math.c

5

And now I have to ask for forgiveness.
The file of the commit ( ba6c22ce938ed ) says "Copyright (c) 2015 Netflix, Inc."

[dumbbell]

Address feedback from @bz.

I also messed up my git-blame(1) invocation…