bitops.h: Add find_first_bit32()
set_bit32()/test_bit32()/etc already let devices operate on guest-visible uint32_t register arrays without depending on the host's 'unsigned long' size. Add find_first_bit32() so callers need not cast a uint32_t array to 'unsigned long *'. Reviewed-by: Pierrick Bouvier <pierrick.bouvier@oss.qualcomm.com> Link: https://lore.kernel.org/qemu-devel/20260806042723.3785369-7-brian.cain@oss.qualcomm.com Signed-off-by: Brian Cain <brian.cain@oss.qualcomm.com>
Brian Cain committed
Aug 5, 2026 at 21:27 UTC
d922df10b27aa9f492638a22b62a43e873246c40
1 file changed
+26
-4
include/qemu/bitops.h
+26
-4
@@ -43,10 +43,9 @@
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* be some guest-visible register view of the bit array.
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*
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* We do not currently implement uint32_t versions of find_last_bit(),
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- * find_next_bit(), find_next_zero_bit(), find_first_bit() or
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- * find_first_zero_bit(), because we haven't yet needed them. If you
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- * need them you should implement them similarly to the 'unsigned long'
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- * versions.
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+ * find_next_bit(), find_next_zero_bit() or find_first_zero_bit(),
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+ * because we haven't yet needed them. If you need them you should
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+ * implement them similarly to the 'unsigned long' versions.
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*
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* You can declare a bitmap to be used with these functions via the
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* DECLARE_BITMAP and DECLARE_BITMAP32 macros in bitmap.h.
@@ -382,6 +381,29 @@ static inline int test_bit32(long nr, const uint32_t *addr)
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return 1U & (addr[BIT32_WORD(nr)] >> (nr & 31));
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}
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+/**
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+ * find_first_bit32 - find the first set bit in a memory region
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+ * @addr: The address to start the search at
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+ * @size: The maximum size to search
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+ *
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+ * Returns the bit number of the first set bit,
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+ * or @size if there is no set bit in the bitmap.
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+ */
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+static inline uint32_t find_first_bit32(const uint32_t *addr, uint32_t size)
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+{
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+ uint32_t result;
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+
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+ for (result = 0; result < size; result += 32) {
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+ uint32_t tmp = *addr++;
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+ if (tmp) {
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+ result += ctz32(tmp);
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+ return result < size ? result : size;
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+ }
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+ }
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+ /* Not found */
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+ return size;
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+}
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+
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/**
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* DOC: Miscellaneous bit operations on single values
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*