From: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Implement fixed-type BIT_U*() to help drivers add stricter checks,
like it was done for GENMASK_U*().
Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx>
Co-developed-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
Signed-off-by: Vincent Mailhol <mailhol.vincent@xxxxxxxxxx>
---
Changelog:
v6 -> v7:
v5 -> v6:
- No changes.
v4 -> v5:
- Rename GENMASK_t() to GENMASK_TYPE().
- Use tab indentations instead of single space to separate the
macro name from its body.
- Add a global comment at the beginning of the file to explain why
GENMASK_U*() and BIT_U*() are not available in asm.
- Add a new BIT_TYPE() helper function, similar to GENMASK_TYPE().
- Remove the unsigned int cast for the U8 and U16 variants. Move
the cast to BIT_TYPE().
- Rename the argument from BIT_U*(b) to BIT_U*(nr) for consistency
with vdso/bits.h.
v3 -> v4:
- Use const_true() to simplify BIT_INPUT_CHECK().
- Make BIT_U8() and BIT_U16() return an unsigned int instead of a
u8 and u16. Because of the integer promotion rules in C, an u8
or an u16 would become a signed integer as soon as these are
used in any expression. By casting these to unsigned ints, at
least the signedness is kept.
- Put the cast next to the BIT() macro.
- In BIT_U64(): use BIT_ULL() instead of BIT().
---
include/linux/bits.h | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/include/linux/bits.h b/include/linux/bits.h
index beb3ee2f1bc74a9346dd72eb06c722a9bc536051..6a942ea9ab380d3bd0e521916caa1d59db8031c0 100644
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -24,7 +24,7 @@
/*
* Missing asm support
*
- * GENMASK_U*() depend on BITS_PER_TYPE() which relies on sizeof(),
+ * GENMASK_U*() and BIT_U*() depend on BITS_PER_TYPE() which relies on sizeof(),
* something not available in asm. Nevertheless, fixed width integers is a C
* concept. Assembly code can rely on the long and long long versions instead.
*/
@@ -55,6 +55,24 @@
#define GENMASK_U32(h, l) GENMASK_TYPE(u32, h, l)
#define GENMASK_U64(h, l) GENMASK_TYPE(u64, h, l)
+/*
+ * Fixed-type variants of BIT(), with additional checks like GENMASK_TYPE(). The
+ * following examples generate compiler warnings due to shift-count-overflow:
+ *
+ * - BIT_U8(8)
+ * - BIT_U32(-1)
+ * - BIT_U32(40)
+ */
+#define BIT_INPUT_CHECK(type, nr) \
+ BUILD_BUG_ON_ZERO(const_true((nr) >= BITS_PER_TYPE(type)))
+
+#define BIT_TYPE(type, nr) ((type)(BIT_INPUT_CHECK(type, nr) + BIT_ULL(nr)))
+
+#define BIT_U8(nr) BIT_TYPE(u8, nr)
+#define BIT_U16(nr) BIT_TYPE(u16, nr)
+#define BIT_U32(nr) BIT_TYPE(u32, nr)
+#define BIT_U64(nr) BIT_TYPE(u64, nr)
+
#else /* defined(__ASSEMBLY__) */
/*
--
2.48.1
