From: <Codrin.Ciubotariu@microchip.com>
To: <michael@walle.cc>, <Tudor.Ambarus@microchip.com>
Cc: <linux-i2c@vger.kernel.org>
Subject: Re: wrong assumption in i2c-at91-master.c ?
Date: Mon, 7 Mar 2022 17:09:43 +0000 [thread overview]
Message-ID: <988d9fb8-eaab-13f1-db5e-189825a16097@microchip.com> (raw)
In-Reply-To: <591de05fde401e8899726e015b837cd1@walle.cc>
On 07.03.2022 17:57, Michael Walle wrote:
> Hi,
Mi Michael,
>
> 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.
The constraints are set using the quirks feature [1] of the i2c subsystem.
Best regards,
Codrin
[1]
https://elixir.bootlin.com/linux/latest/source/drivers/i2c/busses/i2c-at91-master.c#L720
next prev parent reply other threads:[~2022-03-07 17:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-07 15:57 wrong assumption in i2c-at91-master.c ? Michael Walle
2022-03-07 17:09 ` Codrin.Ciubotariu [this message]
2022-03-07 17:23 ` Michael Walle
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