linux-kernel - Re: [PATCH 2/2] NFC: nxp-nci: Don't issue a zero length i2c_master

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Message-ID: <6a429e1e42178d863ce54cf2497b86b3@walle.cc>
Date:   Tue, 28 Jun 2022 08:42:26 +0200
From:   Michael Walle <michael@...le.cc>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Clément Perrochaud 
        <clement.perrochaud@....com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] NFC: nxp-nci: Don't issue a zero length
 i2c_master_read()

Am 2022-06-28 07:03, schrieb Jakub Kicinski:
> On Sun, 26 Jun 2022 21:42:43 +0200 Michael Walle wrote:
>> There are packets which doesn't have a payload. In that case, the 
>> second
>> i2c_master_read() will have a zero length. But because the NFC
>> controller doesn't have any data left, it will NACK the I2C read and
>> -ENXIO will be returned. In case there is no payload, just skip the
>> second i2c master read.
> 
> Whoa, are you using this code or just found the problem thru code
> inspection? NFC is notorious for having no known users.

Ha! Well, I *try* to use it with a PN7160. No luck so far, we'll see.
At least the communication with the chip works now. I was also kinda
tricked by the Supported status ;)

-michael