bitstring: add functions to find contiguous set/unset bit sequences

[jacob.e.keller_intel.com]

Summary

Add bit_ffs_area_at and bit_ffc_area_at functions for searching a bit
string for a sequence of contiguous set or unset bits of at least the
specified size.

The bit_ffc_area function will be used by the Intel ice driver for
implementing resource assignment logic using a bitstring to represent
whether or not a given index has been assigned or is currently free.

The bit_ffs_area, bit_ffc_area_at and bit_ffs_area_at functions are
implemented for completeness.

I'd like to add further test cases for the new functions, but I'm not
really sure how to add them easily. The new functions depend on specific
sequences of bits being set, while the bitstring tests appear to run for
varying bit sizes.

Signed-off-by: Jacob Keller <[e-mail]>

[jacob.e.keller_intel.com]

We use this implementation in the ice driver (current review at https://reviews.freebsd.org/D21959, will be updated to reflect moving the function here soon).

[asomers]

It should be fine to add new tests cases that depend on a specific nbits. Just add them normally instead of using the BITSTRING_TC_DEFINE macro.

share/man/man3/bitstring.3

61

You need to bump this date.

245

in the location

262

in the location

279

in the location

300

in the location

sys/sys/bitstring.h

290

Why not if ( i >= 0)?

322

Why not if (i >= 0)?

[jacob.e.keller_intel.com]

Ok, will add tests and fix the comments.

sys/sys/bitstring.h

290

Sure, makes sense.

[jacob.e.keller_intel.com]

Update review based on feedback from Alan Somers

• Update manual page wording
• Add additional test cases to cover the new functionality in bit_ffs_area_at and bit_ffc_area_at
• Use "i >= 0" instead of "!(i < 0)"

[jacob.e.keller_intel.com]

Updated the review to include additional test cases and fixed the manual page.

[asomers]

tests/sys/sys/bitstring_test.c

335

You can also use ATF_REQUIRE_EQ_MSG here, but it's ok as-is.

375

To ensure that location is actually updated, you should modify it before line 375 and 384. Also 442 and 450. Or maybe just before every call.

[jacob.e.keller_intel.com]

tests/sys/sys/bitstring_test.c

335

Going to use ATF_REQUIRE_EQ_MSG since I need to modify this anyways. It should give better expected vs actual output and appears more idiomatic. Granted, this test file itself doesn't use it anywhere else, but I think it should be used by these new tests.

375

Will modify to reset location before every call to bit_ffs_area* and bit_ffc_area*.

[jacob.e.keller_intel.com]

Update test cases per review feedback