On Fri, Feb 09, 2024 at 08:53:25AM -0800, Yury Norov wrote:
On Wed, Feb 07, 2024 at 11:45:20PM -0800, Lucas De Marchi wrote:
Implement fixed-type BIT() to help drivers add stricter checks, like was
done for GENMASK.
Signed-off-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Acked-by: Jani Nikula <jani.nikula@xxxxxxxxx>
So I get v1 from Jan.23 in my mailbox, and this one is v3. Did I miss
a v2? Anyways, please bear my reviewed-by from v1 for this patch.
Jan 23 was actually the v2 and I missed the subject prefix.
My understanding was that you were going to apply this through some
bitmap tree, but checking MAINTAINERS now it seems there's no git tree
associated. So I will just add your r-b and merge this through
drm-xe.
thanks
Lucas De Marchi
Thanks,
Yury
---
include/linux/bits.h | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/include/linux/bits.h b/include/linux/bits.h
index bd56f32de44e..811846ce110e 100644
--- a/include/linux/bits.h
+++ b/include/linux/bits.h
@@ -24,12 +24,16 @@
#define GENMASK_INPUT_CHECK(h, l) \
(BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
__is_constexpr((l) > (h)), (l) > (h), 0)))
+#define BIT_INPUT_CHECK(type, b) \
+ ((BUILD_BUG_ON_ZERO(__builtin_choose_expr( \
+ __is_constexpr(b), (b) >= BITS_PER_TYPE(type), 0))))
#else
/*
* BUILD_BUG_ON_ZERO is not available in h files included from asm files,
* disable the input check if that is the case.
*/
#define GENMASK_INPUT_CHECK(h, l) 0
+#define BIT_INPUT_CHECK(type, b) 0
#endif
/*
@@ -54,4 +58,17 @@
#define GENMASK_U32(h, l) __GENMASK(u32, h, l)
#define GENMASK_U64(h, l) __GENMASK(u64, h, l)
+/*
+ * Fixed-type variants of BIT(), with additional checks like __GENMASK(). The
+ * following examples generate compiler warnings due to shift-count-overflow:
+ *
+ * - BIT_U8(8)
+ * - BIT_U32(-1)
+ * - BIT_U32(40)
+ */
+#define BIT_U8(b) ((u8)(BIT_INPUT_CHECK(u8, b) + BIT(b)))
+#define BIT_U16(b) ((u16)(BIT_INPUT_CHECK(u16, b) + BIT(b)))
+#define BIT_U32(b) ((u32)(BIT_INPUT_CHECK(u32, b) + BIT(b)))
+#define BIT_U64(b) ((u64)(BIT_INPUT_CHECK(u64, b) + BIT(b)))
+
#endif /* __LINUX_BITS_H */
--
2.43.0
