Re: [PATCH 3/8 v3] i2c: i801: check INTR after every transaction

Jean Delvare
2012-07-02T15:16:51Z

On Mon, 2 Jul 2012 12:08:14 +0200, Jean Delvare wrote:
> On Mon, 2 Jul 2012 09:19:24 +0800, Daniel Kurtz wrote:
> > My understanding is that the INTR wait is really waiting for the
> > entire transaction to complete (ie., including i2c STOP condition),
> > not just the byte transfer phase.
>
> This is my understanding as well, but I'm fairly certain that this is
> the case of the BUSY flag as well. I think BUSY gets cleared at the
> same time INTR (or any of the error status bits) gets set. Which is why
> I think checking BUSY is redundant. As a matter of fact, we ignore BUSY
> completely in i801_block_transaction_byte_by_byte(), so I see no reason
> why we couldn't do the same in i2c_transaction().

To be complete, I made some testing and error bits can be set before
BUSY is cleared. I spotted several transitions 0x41 -> 0x45 -> 0x44
when accessing non-existent devices. On success, I never witnessed INTR
and BUSY being set at the same time, transition is always 0x41 -> 0x42.

--
Jean Delvare