Re: + i2c-fix-i2c-mpc-driver-for-multi-master-i2c-busses.patch added to -mm tree

[David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>]

On Monday 16 February 2009, Jean Delvare wrote:
> > There's no guarantee of idempotency in messages; only
> > callers can know if retrying a given partially completed
> > message is safe.  And since fault reporting is still goofy,
> > we can't know just where arbitration was lost... in the
> > first master transmit, second (after repeated START),
> > third, etc.
> 
> As already explained by Clifford, arbitration loss is about messages
> which have not been transmitted at all. So retrying is always OK.

I must have missed that.  It's not correct, in any case.
Messages can easily have been *partially* transmitted.

Loss of arbitration appears at the first transmitted bit
where one master sends '0' and overrides another, which
is sending '1' instead.  Ideally it's while addressing a
device, but it could be after some data bytes have been
sent ... and, depending on the slave, acted upon.  Even
after one or more repeated starts.

- Dave