On Mon, Jul 17, 2023 at 01:37:04PM +0200, Alexander Potapenko wrote:

The two new functions allow setting/getting values of length up to
BITS_PER_LONG bits at arbitrary position in the bitmap.

The code was taken from "bitops: Introduce the for_each_set_clump macro"
by Syed Nayyar Waris with a couple of minor changes:

Since changes are minor, please make sure that the authorship is kept
untouched.

 - instead of using roundup(), which adds an unnecessary dependency
   on <linux/math.h>, we calculate space as BITS_PER_LONG-offset;
 - indentation is reduced by not using else-clauses (suggested by
   checkpatch for bitmap_get_value())

Cc: Arnd Bergmann <arnd@arndb.de>

You can use --cc to `git send-email` instead of polluting the commit message.

Signed-off-by: Syed Nayyar Waris <redacted>
Signed-off-by: William Breathitt Gray <redacted>
Link: https://lore.kernel.org/lkml/fe12eedf3666f4af5138de0e70b67a07c7f40338.1592224129.git.syednwaris@gmail.com/ (local)
Suggested-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Alexander Potapenko <glider@google.com>

With above, I think you can also add Co-developed-by (as the changes were
made).

...

+static inline void bitmap_set_value(unsigned long *map,
+				    unsigned long value,
+				    unsigned long start, unsigned long nbits)
+{
+	const size_t index = BIT_WORD(start);
+	const unsigned long offset = start % BITS_PER_LONG;
+	const unsigned long space = BITS_PER_LONG - offset;
+
+	value &= GENMASK(nbits - 1, 0);
+
+	if (space >= nbits) {

+		map[index] &= ~(GENMASK(nbits + offset - 1, offset));

I remember that this construction may bring horrible code on some architectures
with some version(s) of the compiler (*).

To fix that I found an easy refactoring:

		map[index] &= ~(GENMASK(nbits, 0) << offset));


(*) don't remember the actual versions, though, but anyway...

+		map[index] |= value << offset;
+		return;
+	}
+	map[index] &= ~BITMAP_FIRST_WORD_MASK(start);
+	map[index] |= value << offset;
+	map[index + 1] &= ~BITMAP_LAST_WORD_MASK(start + nbits);
+	map[index + 1] |= (value >> space);
+}

-- 
With Best Regards,
Andy Shevchenko



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