libchip/m48t08 driver

[Joel Sherrill]

Till Straumann wrote:
> I thought about merging some extended features
> I implemented in BSP specific drivers for m48txx
> series RTC chips into the generic libchip version.
>
> Looking at that one (i.e., libchip/rtc/m48t08.c),
> I found that it is not thread safe.
>
> RFC: Would it be acceptable for this
> driver to use a mutex?
>
>   
Before doing that .. Does it do things that would be too inappropriate 
for simply
disabling preemption or interrupts?  Disabling preemption for short 
periods of
time is no worse on latency than calling a pair of directives.

Otherwise, a mutex is OK.

> - T.
>
>
>
>