Add inlined functions to obtain a mask of changed bits. 3 flavors
are added: toggled, changed to 1, changed to 0.
These newly added utilities aid common device behaviors where
actions are taken only when a register's bit(s) are changed.
Signed-off-by: Tong Ho <tong...@amd.com>
---
include/qemu/bitops.h | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/include/qemu/bitops.h b/include/qemu/bitops.h
index 2c0a2fe751..7a701474ea 100644
--- a/include/qemu/bitops.h
+++ b/include/qemu/bitops.h
@@ -148,6 +148,39 @@ static inline int test_bit(long nr, const unsigned long
*addr)
return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
}
+/**
+ * find_bits_changed - Returns a mask of bits changed.
+ * @ref_bits: the reference bits against which the test is made.
+ * @chk_bits: the bits to be checked.
+ */
+static inline unsigned long find_bits_changed(unsigned long ref_bits,
+ unsigned long chk_bits)
+{
+ return ref_bits ^ chk_bits;
+}
+
+/**
+ * find_bits_to_1 - Returns a mask of bits changed from 0 to 1.
+ * @ref_bits: the reference bits against which the test is made.
+ * @chk_bits: the bits to be checked.
+ */
+static inline unsigned long find_bits_to_1(unsigned long ref_bits,
+ unsigned long chk_bits)
+{
+ return find_bits_changed(ref_bits, chk_bits) & chk_bits;
+}
+
+/**
+ * find_bits_to_0 - Returns a mask of bits changed from 1 to 0.
+ * @ref_bits: the reference bits against which the test is made.
+ * @chk_bits: the bits to be checked.
+ */
+static inline unsigned long find_bits_to_0(unsigned long ref_bits,
+ unsigned long chk_bits)
+{
+ return find_bits_to_1(chk_bits, ref_bits);
+}
+
/**
* find_last_bit - find the last set bit in a memory region
* @addr: The address to start the search at
--
2.25.1
