bitmap: introduce hardware-specific bitfield operations

2025-09-02T23:59:16+00:00

Hardware of various vendors, but very notably Rockchip, often uses 32-bit registers where the upper 16-bit half of the register is a write-enable mask for the lower half. This type of hardware setup allows for more granular concurrent register write access. Over the years, many drivers have hand-rolled their own version of this macro, usually without any checks, often called something like HIWORD_UPDATE or FIELD_PREP_HIWORD, commonly with slightly different semantics between them. Clearly there is a demand for such a macro, and thus the demand should be satisfied in a common header file. As this is a convention that spans across multiple vendors, and similar conventions may also have cross-vendor adoption, it's best if it lives in a vendor-agnostic header file that can be expanded over time. Add hw_bitfield.h with two macros: FIELD_PREP_WM16, and FIELD_PREP_WM16_CONST. The latter is a version that can be used in initializers, like FIELD_PREP_CONST. Suggested-by: Yury Norov (NVIDIA) Signed-off-by: Nicolas Frattaroli Acked-by: Jakub Kicinski Acked-by: Heiko Stuebner Signed-off-by: Yury Norov (NVIDIA)

kernel/linux.git/include/linux/hw_bitfield.h, branch v6.19.11

bitmap: introduce hardware-specific bitfield operations