On Wed, Jan 06, 2021 at 03:52:14PM +0000, Ionela Voinescu wrote: > > > > > vim +367 arch/arm64/kernel/topology.c > > > > > > > > > > 362 > > > > > 363 int cpc_read_ffh(int cpu, struct cpc_reg *reg, u64 *val) > > > > > 364 { > > > > > 365 int ret = -EOPNOTSUPP; > > > > > 366 > > > > > > 367 switch ((u64)reg->address) { > > > > > > > > That's not a dereference but I guess sparse complains of dropping the > > > > __iomem. We could change the cast to (__force u64) to silence sparse. > > > > > > > > Thanks for the report. > > > > > > > > > > Nothing I've tried seemed to silence sparse here, including casting to > > > (__force u64). > > > > Would it work if we changed the case lines to (u64 __iomem)0x0? > > > > No, it does not. We still get the same warning on the switch line even > if there is no cast. Same if we directly check for: > > if (reg->address == (u64 __iomem)0x0)
Folks, could you stop with the voodoo? This u64 __iomem address thing is completely wrong. What it says is "address of that field shall be an iomem pointer", which makes no sense whatsoever. Just what had been intended? __iomem is a qualifier of the same sort as const or volatile - this mess makes as much sense as struct cpc_reg { u8 descriptor; u16 length; u8 space_id; u8 bit_width; u8 bit_offset; u8 access_width; u64 const address; } __packed; Which would *NOT* be read as "reg->address is a numeric representation of address of something unmodifiable" - it would be "the value stored in reg->address can not be modified". This annotation says "reg->address (somehow) lives in iomem", resulting in "so why the hell are you trying to read it by plain dereferencing of reg + field offset?" from sparse. Get rid of this misannotation and don't breed force-cast to confuse everything hard enough to STFU.