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MMIO needs that gate because > readq() is not available on 32bit. System memory has no such dependency: > a u64 volatile load/store compiles on any architecture, it's just not > single-copy atomic on 32bit. > > Drop the gate so u64-backed types, such as bitfields, work on 32bit too. > Document the non-atomicity at the impl instead of enforcing it at build > time. > > Co-developed-by: Daniel Almeida > Signed-off-by: Daniel Almeida > Signed-off-by: Laura Nao No. If you don't need atomicity, please use `copy_read` to read the value. = It'll compile down to the same volatile read, just without atomicity guarantee. Best, Gary > --- > rust/kernel/io.rs | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/rust/kernel/io.rs b/rust/kernel/io.rs > index de8ef8e2aec4..a85ddd07cb7f 100644 > --- a/rust/kernel/io.rs > +++ b/rust/kernel/io.rs > @@ -1428,7 +1428,9 @@ fn io_write(view: SysMem<'_, $ty>, value: $ty) { > impl_sysmem_io_capable!(u8); > impl_sysmem_io_capable!(u16); > impl_sysmem_io_capable!(u32); > -#[cfg(CONFIG_64BIT)] > +// Unlike MMIO, that needs `readq` which is not available on 32-bit, a > +// system-memory `u64` access compiles on any target. It is just not > +// single-copy atomic on 32-bit. > impl_sysmem_io_capable!(u64); > =20 > impl IoCopyable for SysMemBackend {