linux-kernel - Re: [PATCH] i2c: k1: check for transfer error

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Message-ID: <d7f7dc4c-5d2a-4f63-9451-5e4d2e53cf1b@riscstar.com>
Date: Thu, 12 Jun 2025 21:16:05 -0500
From: Alex Elder <elder@...cstar.com>
To: Troy Mitchell <troymitchell988@...il.com>, andi.shyti@...nel.org,
 dlan@...too.org
Cc: linux-i2c@...r.kernel.org, spacemit@...ts.linux.dev,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Troy Mitchell <troy.mitchell@...ux.dev>
Subject: Re: [PATCH] i2c: k1: check for transfer error

On 6/12/25 9:12 PM, Troy Mitchell wrote:
> On Thu, Jun 12, 2025 at 05:56:25PM -0500, Alex Elder wrote:
>> If spacemit_i2c_xfer_msg() times out waiting for a message transfer to
>> complete, or if the hardware reports an error, it returns a negative
>> error code (-ETIMEDOUT, -EAGAIN, -ENXIO. or -EIO).
>>
>> The sole caller of spacemit_i2c_xfer_msg() is spacemit_i2c_xfer(),
>> which is the i2c_algorithm->xfer callback function.  It currently
>> does not save the value returned by spacemit_i2c_xfer_msg().
>>
>> The result is that transfer errors go unreported, and a caller
>> has no indication anything is wrong.
>>
>> When this code was out for review, the return value *was* checked
>> in early versions.  But for some reason, that assignment got dropped
>> between versions 5 and 6 of the series, perhaps related to reworking
>> the code to merge spacemit_i2c_xfer_core() into spacemit_i2c_xfer().
>>
>> Simply assigning the value returned to "ret" fixes the problem.
>>
>> Fixes: 5ea558473fa31 ("i2c: spacemit: add support for SpacemiT K1 SoC")
>> Signed-off-by: Alex Elder <elder@...cstar.com>
>> Reviewed-by: Troy Mitchell <troymitchell988@...il.com>
>> ---
>> v2: Added Troy's Reviewed-by
> Hi Alex, you added the changelog, but the subject line
> doesn't have the "V2" suffix. Is this a mistake?

Yes it's a mistake.  I contemplated sending an immediate
"oops, this was v2!!!" but opted to wait until someone
like you asked about it.

This *is* version 2, and I made the updates I describe.

					-Alex
> 
>              - Troy
> 
>>
>>   drivers/i2c/busses/i2c-k1.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-k1.c b/drivers/i2c/busses/i2c-k1.c
>> index 5965b4cf6220e..b68a21fff0b56 100644
>> --- a/drivers/i2c/busses/i2c-k1.c
>> +++ b/drivers/i2c/busses/i2c-k1.c
>> @@ -477,7 +477,7 @@ static int spacemit_i2c_xfer(struct i2c_adapter *adapt, struct i2c_msg *msgs, in
>>   
>>   	ret = spacemit_i2c_wait_bus_idle(i2c);
>>   	if (!ret)
>> -		spacemit_i2c_xfer_msg(i2c);
>> +		ret = spacemit_i2c_xfer_msg(i2c);
>>   	else if (ret < 0)
>>   		dev_dbg(i2c->dev, "i2c transfer error: %d\n", ret);
>>   	else
>>
>> base-commit: 19272b37aa4f83ca52bdf9c16d5d81bdd1354494
>> -- 
>> 2.45.2
>>