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Date:   Mon, 07 Mar 2022 16:57:27 +0100
From:   Michael Walle <michael@walle.cc>
To:     Codrin Ciubotariu <codrin.ciubotariu@microchip.com>,
        Tudor Ambarus <Tudor.Ambarus@microchip.com>
Cc:     linux-i2c@vger.kernel.org
Subject: wrong assumption in i2c-at91-master.c ?
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Hi,

I saw that the at91 i2c driver has some kind of heuristic in
at91_twi_xfer(). It assumes that if there are exactly two
messages to transfer, the first is the address write of a
common i2c write address, read data transaction. I don't
think that assumption is correct.

Also there is no check if msg->len is actually smaller
than the width of the address which can be written to
AT91_TWI_IADR.

I think, what is at least missing is that, the first
one is actually a write and have at max 3 bytes (IIRC
thats the max width of AT91_TWI_IADR).

Actually, I don't find any code at all which would
handle multiple messages. Looks like it just supports
num == 2 (and assumes the first message fits into the
AT91_TWI_IADR) and num == 1.

-michael