Re: [PATCH 3/9] bitmap: Use FIELD_PREP() in expansion of FIELD_PREP_WM16()

Nicolas Frattaroli
2025-12-10T19:19:24Z

On Tuesday, 9 December 2025 11:03:07 Central European Standard Time david.laight.linux@gmail.com wrote:
> From: David Laight <david.laight.linux@gmail.com>
>
> Instead of directly expanding __BF_FIELD_CHECK() (which really ought
> not be used outside bitfield) and open-coding the generation of the
> masked value, just call FIELD_PREP() and add an extra check for
> the mask being at most 16 bits.
>
> Signed-off-by: David Laight <david.laight.linux@gmail.com>
> ---
> include/linux/hw_bitfield.h | 17 ++++++++---------
> 1 file changed, 8 insertions(+), 9 deletions(-)
>
> diff --git a/include/linux/hw_bitfield.h b/include/linux/hw_bitfield.h
> index df202e167ce4..d7f21b60449b 100644
> --- a/include/linux/hw_bitfield.h
> +++ b/include/linux/hw_bitfield.h
> @@ -23,15 +23,14 @@
> * register, a bit in the lower half is only updated if the corresponding bit
> * in the upper half is high.
> */
> -#define FIELD_PREP_WM16(_mask, _val) \
> - ({ \
> - typeof(_val) __val = _val; \
> - typeof(_mask) __mask = _mask; \
> - __BF_FIELD_CHECK(__mask, ((u16)0U), __val, \
> - "HWORD_UPDATE: "); \
> - (((typeof(__mask))(__val) << __bf_shf(__mask)) & (__mask)) | \
> - ((__mask) << 16); \
> - })
> +#define FIELD_PREP_WM16(mask, val) \
> +({ \
> + __auto_type _mask = mask; \
> + u32 _val = FIELD_PREP(_mask, val); \
> + BUILD_BUG_ON_MSG(_mask > 0xffffu, \
> + "FIELD_PREP_WM16: mask too large"); \
> + _val | (_mask << 16); \
> +})
>
> /**
> * FIELD_PREP_WM16_CONST() - prepare a constant bitfield element with a mask in
>

This breaks the build for at least one driver that uses
FIELD_PREP_WM16, namely phy-rockchip-emmc.c:

drivers/phy/rockchip/phy-rockchip-emmc.c:109:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
109 | HIWORD_UPDATE(PHYCTRL_PDB_PWR_OFF,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:114:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
114 | HIWORD_UPDATE(PHYCTRL_ENDLL_DISABLE,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:167:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
167 | HIWORD_UPDATE(PHYCTRL_PDB_PWR_ON,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:190:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
190 | HIWORD_UPDATE(freqsel, PHYCTRL_FREQSEL_MASK,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:196:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
196 | HIWORD_UPDATE(PHYCTRL_ENDLL_ENABLE,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:291:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
291 | HIWORD_UPDATE(rk_phy->drive_impedance,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:298:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
298 | HIWORD_UPDATE(PHYCTRL_OTAPDLYENA,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:305:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
305 | HIWORD_UPDATE(rk_phy->output_tapdelay_select,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:312:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
312 | HIWORD_UPDATE(rk_phy->enable_strobe_pulldown,
| ^
drivers/phy/rockchip/phy-rockchip-emmc.c:25:4: note: expanded from macro 'HIWORD_UPDATE'
25 | (FIELD_PREP_WM16((mask) << (shift), (val)))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^

Maybe the wrapping in HIWORD_UPDATE (which was done to make the
transitionary patch easier) is playing a role here.

pcie-dw-rockchip.c is similarly broken by this change, except
without the superfluous wrapper:

drivers/pci/controller/dwc/pcie-dw-rockchip.c:191:37: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
191 | rockchip_pcie_writel_apb(rockchip, PCIE_CLIENT_ENABLE_LTSSM,
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:43:35: note: expanded from macro 'PCIE_CLIENT_ENABLE_LTSSM'
43 | #define PCIE_CLIENT_ENABLE_LTSSM FIELD_PREP_WM16(BIT(2), 1)
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:197:37: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
197 | rockchip_pcie_writel_apb(rockchip, PCIE_CLIENT_DISABLE_LTSSM,
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:44:36: note: expanded from macro 'PCIE_CLIENT_DISABLE_LTSSM'
44 | #define PCIE_CLIENT_DISABLE_LTSSM FIELD_PREP_WM16(BIT(2), 0)
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:222:38: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
222 | rockchip_pcie_writel_apb(rockchip, PCIE_CLKREQ_READY,
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:67:29: note: expanded from macro 'PCIE_CLKREQ_READY'
67 | #define PCIE_CLKREQ_READY FIELD_PREP_WM16(BIT(0), 1)
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:234:6: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
234 | PCIE_CLKREQ_PULL_DOWN | PCIE_CLKREQ_NOT_READY,
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:69:33: note: expanded from macro 'PCIE_CLKREQ_PULL_DOWN'
69 | #define PCIE_CLKREQ_PULL_DOWN FIELD_PREP_WM16(GENMASK(13, 12), 1)
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:234:30: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
234 | PCIE_CLKREQ_PULL_DOWN | PCIE_CLKREQ_NOT_READY,
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:68:33: note: expanded from macro 'PCIE_CLKREQ_NOT_READY'
68 | #define PCIE_CLKREQ_NOT_READY FIELD_PREP_WM16(BIT(0), 0)
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:535:9: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
535 | val = FIELD_PREP_WM16(PCIE_LTSSM_APP_DLY2_DONE, 1);
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:574:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
574 | val = FIELD_PREP_WM16(PCIE_LTSSM_ENABLE_ENHANCE, 1);
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:578:6: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
578 | PCIE_CLIENT_SET_MODE(PCIE_CLIENT_MODE_RC),
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:41:34: note: expanded from macro 'PCIE_CLIENT_SET_MODE'
41 | #define PCIE_CLIENT_SET_MODE(x) FIELD_PREP_WM16(PCIE_CLIENT_MODE_MASK, (x))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:592:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
592 | val = FIELD_PREP_WM16(PCIE_RDLH_LINK_UP_CHGED, 0);
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:624:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
624 | val = FIELD_PREP_WM16(PCIE_LTSSM_ENABLE_ENHANCE, 1) |
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:625:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
625 | FIELD_PREP_WM16(PCIE_LTSSM_APP_DLY2_EN, 1);
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:629:6: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
629 | PCIE_CLIENT_SET_MODE(PCIE_CLIENT_MODE_EP),
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:41:34: note: expanded from macro 'PCIE_CLIENT_SET_MODE'
41 | #define PCIE_CLIENT_SET_MODE(x) FIELD_PREP_WM16(PCIE_CLIENT_MODE_MASK, (x))
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:653:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
653 | val = FIELD_PREP_WM16(PCIE_RDLH_LINK_UP_CHGED, 0) |
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
drivers/pci/controller/dwc/pcie-dw-rockchip.c:654:8: error: variable '_mask' declared with deduced type '__auto_type' cannot appear in its own initializer
654 | FIELD_PREP_WM16(PCIE_LINK_REQ_RST_NOT_INT, 0);
| ^
include/linux/hw_bitfield.h:29:24: note: expanded from macro 'FIELD_PREP_WM16'
29 | u32 _val = FIELD_PREP(_mask, val); \
| ^
14 errors generated.

Kind regards,
Nicolas Frattaroli