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"Walter J. <walter...@oss.cipunited.com>" just uploaded a new patch set to
Gerrit, which you can find at https://review.openocd.org/c/openocd/+/8171
-- gerrit
commit 83a229f5093beec55db964ee13fe29d27a32a239
Author: Walter Ji <walter...@oss.cipunited.com>
Date: Mon Mar 4 17:29:15 2024 +0800
helper: add bitfield helper macros
This patch ports FIELD_GET and FIELD_PREP macro and related macro
from linux kernel, referenced file:
- include/linux/bitfield.h
Checkpatch-ignore: MACRO_ARG_REUSE
Change-Id: I6fdf4514d3f95d62fadf7654409a4878d470a600
Signed-off-by: Walter Ji <walter...@oss.cipunited.com>
diff --git a/src/helper/bitfield.h b/src/helper/bitfield.h
new file mode 100644
index 0000000000..3a5d9f497e
--- /dev/null
+++ b/src/helper/bitfield.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+/*
+ * Copyright (C) 2024 by Shixin 'Walter' Ji
+ * walter...@cipunited.com
+ */
+
+/*
+ * The content of this file is copied/inspired from Linux kernel, too.
+ * Referenced code in include/linux/bitfield.h
+ */
+
+#ifndef OPENOCD_HELPER_BITFIELD_H
+#define OPENOCD_HELPER_BITFIELD_H
+
+/*
+ * Bitfield access macros
+ *
+ * FIELD_{GET,PREP} macros take as first parameter shifted mask
+ * from which they extract the base mask and shift amount.
+ * Mask must be a compilation time constant.
+ *
+ * Example:
+ *
+ * #include <helper/bitfield.h>
+ * #include <helper/bits.h>
+ *
+ * #define REG_FIELD_A GENMASK(6, 0)
+ * #define REG_FIELD_B BIT(7)
+ * #define REG_FIELD_C GENMASK(15, 8)
+ * #define REG_FIELD_D GENMASK(31, 16)
+ *
+ * Get:
+ * a = FIELD_GET(REG_FIELD_A, reg);
+ * b = FIELD_GET(REG_FIELD_B, reg);
+ *
+ * Set:
+ * reg = FIELD_PREP(REG_FIELD_A, 1) |
+ * FIELD_PREP(REG_FIELD_B, 0) |
+ * FIELD_PREP(REG_FIELD_C, c) |
+ * FIELD_PREP(REG_FIELD_D, 0x40);
+ *
+ * Modify:
+ * reg &= ~REG_FIELD_C;
+ * reg |= FIELD_PREP(REG_FIELD_C, c);
+ */
+
+/* Returns the index of the least significant 1-bit of x, returns zero when x
is 0. */
+#define __bf_shf(x) (__builtin_ffsll(x) - 1)
+
+/**
+ * FIELD_PREP() - prepare a bitfield element
+ * @_mask: shifted mask defining the field's length and position
+ * @_val: value to put in the field
+ *
+ * FIELD_PREP() masks and shifts up the value. The result should
+ * be combined with other fields of the bitfield using logical OR.
+ */
+#define FIELD_PREP(_mask, _val) (((typeof(_mask))(_val) <<
__bf_shf(_mask)) & (_mask))
+
+/**
+ * FIELD_GET() - extract a bitfield element
+ * @_mask: shifted mask defining the field's length and position
+ * @_reg: value of entire bitfield
+ *
+ * FIELD_GET() extracts the field specified by @_mask from the
+ * bitfield passed in as @_reg by masking and shifting it down.
+ */
+#define FIELD_GET(_mask, _reg) ((typeof(_mask))(((_reg) & (_mask)) >>
__bf_shf(_mask)))
+
+#endif /* OPENOCD_HELPER_BITFIELD_H */
--
