Why sys_set_bit() and sys_clear_bit() don't use sys_read*()

[yashi]

Is there any reason why we don't use sys_read32() and sys_write32() from sys_set_bit()? #27098 describes them as :

• sys_io.h - generic MMIO accessors implementation
• sys_bitops.h - generic memory bits manipulation functions implementation

So, is it wrong to assume that we can use sys_set_bit() for MMIOs? There seems to be many device drivers using sys_set_bit() and sys_clear_bit() for MMIO, IIUC.

The thing is that some (many?) arch has memory barriers in sys_read*() and sys_write*(). But functions from sys_bitops.h don't.