Using of cached values

[Mogambo Park]

good morning

  I wants to know - How safe to read register values one time in a structure
and use value from there, assume no write is performed on the
register? I see many
files in sound/soc/codec/ do that.

is it becos sometime the register may return not accurate value on
busy bus by h/w mistake?
OR I should always read from register even if his value is not
expected to change?

lot thanks