[PATCH 1/2] include: sbi_bitmap: add bitmap_empty() function - Yu-Chien Peter Lin

From: Yu-Chien Peter Lin <peter.lin@sifive.com>
To: opensbi@lists.infradead.org
Cc: Yu-Chien Peter Lin <peter.lin@sifive.com>
Subject: [PATCH 1/2] include: sbi_bitmap: add bitmap_empty() function
Date: Wed, 11 Mar 2026 20:51:15 +0800	[thread overview]
Message-ID: <20260311125116.1401002-1-peter.lin@sifive.com> (raw)

Add bitmap_empty() to check if bitmap has no bits set.

Unlike bitmap_weight() which calls sbi_popcount() on every word,
bitmap_empty() uses simple non-zero comparisons with early exit.

Signed-off-by: Yu-Chien Peter Lin <peter.lin@sifive.com>
---
 include/sbi/sbi_bitmap.h | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/include/sbi/sbi_bitmap.h b/include/sbi/sbi_bitmap.h
index 596bcc7d..80d3fe3b 100644
--- a/include/sbi/sbi_bitmap.h
+++ b/include/sbi/sbi_bitmap.h
@@ -143,4 +143,20 @@ static inline int bitmap_weight(const unsigned long *src, int nbits)
 	return res;
 }
 
+static inline bool bitmap_empty(const unsigned long *src, int nbits)
+{
+	if (nbits == 0)
+		return true;
+
+	if (small_const_nbits(nbits))
+		return !(*src & BITMAP_LAST_WORD_MASK(nbits));
+	else {
+		size_t i, len = BITS_TO_LONGS(nbits);
+		for (i = 0; i < len - 1; i++)
+			if (src[i])
+				return false;
+		return !(src[len - 1] & BITMAP_LAST_WORD_MASK(nbits));
+	}
+}
+
 #endif
-- 
2.53.0


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