From 416eb60317c64676d158dffea150762930ec008f Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Fri, 23 Feb 2024 10:01:46 +0100 Subject: [PATCH] bitfield: suppress "dubious: x & !y" sparse warning There's a somewhat common pattern of using FIELD_PREP() even for single bits, e.g. cmd->info1 |= FIELD_PREP(HTT_SRNG_SETUP_CMD_INFO1_RING_FLAGS_MSI_SWAP, !!(params.flags & HAL_SRNG_FLAGS_MSI_SWAP)); which might as well be written as if (params.flags & HAL_SRNG_FLAGS_MSI_SWAP) cmd->info1 |= HTT_SRNG_SETUP_CMD_INFO1_RING_FLAGS_MSI_SWAP; (since info1 is fully initialized to start with), but in a long chain of FIELD_PREP() this really seems fine. However, it triggers a sparse warning, in the check in the macro for whether a constant value fits into the mask, as this contains a "& (_val)". In this case, this really is always intentional, so just suppress the warning by adding "0+" to the expression, indicating explicitly that this is correct. Signed-off-by: Johannes Berg Signed-off-by: Kalle Valo Link: https://msgid.link/20240223100146.d243b6b1a9a1.I033828b1187c6bccf086e31400f7e933bb8373e7@changeid --- include/linux/bitfield.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/bitfield.h b/include/linux/bitfield.h index ebfa12f69501..63928f173223 100644 --- a/include/linux/bitfield.h +++ b/include/linux/bitfield.h @@ -66,7 +66,8 @@ _pfx "mask is not constant"); \ BUILD_BUG_ON_MSG((_mask) == 0, _pfx "mask is zero"); \ BUILD_BUG_ON_MSG(__builtin_constant_p(_val) ? \ - ~((_mask) >> __bf_shf(_mask)) & (_val) : 0, \ + ~((_mask) >> __bf_shf(_mask)) & \ + (0 + (_val)) : 0, \ _pfx "value too large for the field"); \ BUILD_BUG_ON_MSG(__bf_cast_unsigned(_mask, _mask) > \ __bf_cast_unsigned(_reg, ~0ull), \ -- 2.20.1