linux-kernel - Re: [PATCH 1/2] NFC: nxp-nci: check return code of i2c_master

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Date:   Sun, 26 Jun 2022 21:55:16 +0200
From:   Michael Walle <michael@...le.cc>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Charles Gorand <charles.gorand@...innov.com>,
        Clément Perrochaud 
        <clement.perrochaud@....com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] NFC: nxp-nci: check return code of i2c_master_recv()

Am 2022-06-26 21:49, schrieb Krzysztof Kozlowski:
> On 26/06/2022 21:42, Michael Walle wrote:
>> Check the return code of i2c_master_recv() for actual errors and
>> propagate it to the caller.
>> 
>> Fixes: 6be88670fc59 ("NFC: nxp-nci_i2c: Add I2C support to NXP NCI 
>> driver")
> 
> The check was there, so I don't see here bug. The only thing missing 
> was
> a bit more detailed error message (without cast to %u) and propagating
> error code instead of EBADMSG, but these are not bugs. The commit msg
> should sound different and Fixes tag is not appropriate.

Well one could argue the nfc_err() is very misleading as it prints
an unreasonable large number. Will remove the Fixes tag and reword
the commit message.

>> Signed-off-by: Michael Walle <michael@...le.cc>
>> ---
>>  drivers/nfc/nxp-nci/i2c.c | 5 ++++-
>>  1 file changed, 4 insertions(+), 1 deletion(-)
>> 
>> diff --git a/drivers/nfc/nxp-nci/i2c.c b/drivers/nfc/nxp-nci/i2c.c
>> index 7e451c10985d..9c80d5a6d56b 100644
>> --- a/drivers/nfc/nxp-nci/i2c.c
>> +++ b/drivers/nfc/nxp-nci/i2c.c
>> @@ -163,7 +163,10 @@ static int nxp_nci_i2c_nci_read(struct 
>> nxp_nci_i2c_phy *phy,
>>  	skb_put_data(*skb, (void *)&header, NCI_CTRL_HDR_SIZE);
>> 
>>  	r = i2c_master_recv(client, skb_put(*skb, header.plen), 
>> header.plen);
>> -	if (r != header.plen) {
>> +	if (r < 0) {
>> +		nfc_err(&client->dev, "I2C receive error %pe\n", ERR_PTR(r));
> 
> Print just 'r'.

Personally, I prefer seeing the actual error string and this idiom is
also used in other drivers. But I wont insist, will change it.

> 
>> +		goto nci_read_exit_free_skb;
>> +	} else if (r != header.plen) {
>>  		nfc_err(&client->dev,
>>  			"Invalid frame payload length: %u (expected %u)\n",
>>  			r, header.plen);
> 
> 
> Best regards,
> Krzysztof

-michael