On Fri, 6 May 2022, Geert Uytterhoeven wrote:

A loooong time ago,  it was suggested to add register accessor
functions to struct device, so e.g. readl(dev, offset) would call
into these accessors, which would implement the bus-specific behavior.
No more worries about readl(), __raw_readl(), ioread32b(), or whatever
quirk is needed, at the (small on nowadays' machines) expense of
some indirection...

 I guess you'd need an additional parameter for the endianness policy 
required (to match either bit or byte lanes, according to ultimate data 
interpretation) where crossing between buses of a different endianness 
each.  Otherwise you'd end up with the mess elsewhere.

  Maciej