linux-kernel - Re: [PATCH v2] i2c: i2c-cros-ec-tunnel: Reduce logging noise

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Message-ID: <CAD=FV=XEFuDKyA2sZCOze=KvatuH3qH8E69qkVW7RsVUzUNgDw@mail.gmail.com>
Date:	Tue, 26 Jul 2016 11:20:31 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Guenter Roeck <linux@...ck-us.net>
Cc:	Wolfram Sang <wsa@...-dreams.de>,
	"linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] i2c: i2c-cros-ec-tunnel: Reduce logging noise

Hi,

On Mon, Jul 25, 2016 at 1:58 PM, Guenter Roeck <linux@...ck-us.net> wrote:
> If an i2c access through i2c-cros-ec-tunnel returns an error, the following
> log message is seen on the console.
>
> cros-ec-i2c-tunnel ff200000.spi:ec@0:i2c-tunnel:
>                         Error parsing EC i2c message -121
>
> This can happen a lot if, for example, the i2c-detect command is executed.
>
> Since it is perfectly normal for an i2c controller to report an error,
> drop the message. Also, report -ENXIO instead of -EREMOTEIO if the access
> error is due to NAK from the device, and return -EIO instead of -EREMOTEIO
> for unknown errors, as suggested in Documentation/i2c/fault-codes.
>
> Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> ---
> v2: Drop message entirely instead of replacing it with dev_dbg,
>     and return -EIO instead of -EREMOTEIO for unknown errors.
>
>  drivers/i2c/busses/i2c-cros-ec-tunnel.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-cros-ec-tunnel.c b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> index a0d95ff682ae..7b9b2ff97d77 100644
> --- a/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> +++ b/drivers/i2c/busses/i2c-cros-ec-tunnel.c
> @@ -154,8 +154,10 @@ static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
>         resp = (const struct ec_response_i2c_passthru *)buf;
>         if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
>                 return -ETIMEDOUT;
> -       else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
> -               return -EREMOTEIO;
> +       else if (resp->i2c_status & EC_I2C_STATUS_NAK)
> +               return -ENXIO;
> +       else if (resp->i2c_status)

IMHO this should continue to be checking (resp->i2c_status &
EC_I2C_STATUS_ERROR).  There is no guarantee that all future status
bits will be errors but that #define should continue to be updated to
be all bits that are errors:

/* Any error */
#define EC_I2C_STATUS_ERROR (EC_I2C_STATUS_NAK | EC_I2C_STATUS_TIMEOUT)


> +               return -EIO;
>
>         /* Other side could send us back fewer messages, but not more */
>         if (resp->num_msgs > *num)
> @@ -222,10 +224,8 @@ static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
>         }
>
>         result = ec_i2c_parse_response(msg->data, i2c_msgs, &num);
> -       if (result < 0) {
> -               dev_err(dev, "Error parsing EC i2c message %d\n", result);
> +       if (result < 0)

Personally I wouldn't expect an i2c timeout and I would love i2c
timeouts to continue to be noisy.  ...but if others don't feel the
same way then I don't feel strongly.

Obviously NAKs shouldn't be noisy.  I'm terribly surprised that they
were before.  I know I've run i2cdetect before and not seen the noise.
Ah, I see.  Looks like this noisiness was introduced in commit
a841178445bb ("mfd: cros_ec: Use a zero-length array for command
data")



-Doug