linux-kernel - Re: [PATCH v2] ASoC: cros_ec_codec: Log results when EC commands fail

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Date:   Fri, 3 Jul 2020 11:19:14 +0200
From:   Enric Balletbo i Serra <enric.balletbo@...labora.com>
To:     Yu-Hsuan Hsu <yuhsuan@...omium.org>
Cc:     ALSA development <alsa-devel@...a-project.org>,
        Takashi Iwai <tiwai@...e.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tzung-Bi Shih <tzungbi@...gle.com>,
        Mark Brown <broonie@...nel.org>,
        Guenter Roeck <groeck@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Cheng-Yi Chiang <cychiang@...omium.org>
Subject: Re: [PATCH v2] ASoC: cros_ec_codec: Log results when EC commands fail

Hi Yu-Hsuan,

On 3/7/20 10:48, Yu-Hsuan Hsu wrote:
> Enric Balletbo i Serra <enric.balletbo@...labora.com> 於 2020年7月3日 週五 下午4:38寫道：
>>
>> Hi Yu-Hsuan,
>>
>> Thank you for your patch
>>
>> On 3/7/20 9:19, Yu-Hsuan Hsu wrote:
>>> Log results of failed EC commands to identify a problem more easily.
>>>
>>> Replace cros_ec_cmd_xfer_status with cros_ec_cmd_xfer because the result
>>> has already been checked in this function. The wrapper is not needed.
>>>
>>
>> Nack, we did an effort to remove all public users of cros_ec_cmd_xfer() in
>> favour of cros_ec_cmd_xfer_status() and you are reintroducing again. You can do
>> the same but using cros_ec_cmd_xfer_status(). In fact, your patch will not build
>> on top of the upcoming changes.
> Thanks! But I have a question about implementing it. Does it look like
> the one below?
> ret = cros_ec_cmd_xfer_status(ec_dev, msg);
> if (ret < 0) {

In this case will already print an error.

What are you trying to achieve?

If the only reason is of this patch is print a message you should either, or
enable dynamic printk and enable dev_dbg or event better use the kernel trace
functionality. There is no need to be more verbose.

Example:
    $ echo 1 > /sys/kernel/debug/tracing/events/cros_ec/enable
    $ cat /sys/kernel/debug/tracing/trace

    369.416372: cros_ec_request_start: version: 0, command: EC_CMD_USB_PD_POWER_INFO
    369.420528: cros_ec_request_done: version: 0, command:
EC_CMD_USB_PD_POWER_INFO, ec result: EC_RES_SUCCESS, retval: 16

Cheers,
 Enric

>   if (ret == -EPROTO)
>     dev_err(..., msg->result)
>   goto error;
> }
> I'm not sure whether it makes sense to check ret == -EPROTO here.
> 
>>
>>> Signed-off-by: Yu-Hsuan Hsu <yuhsuan@...omium.org>
>>> ---
>>>  sound/soc/codecs/cros_ec_codec.c | 9 ++++++++-
>>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/sound/soc/codecs/cros_ec_codec.c b/sound/soc/codecs/cros_ec_codec.c
>>> index 8d45c628e988e..a4ab62f59efa6 100644
>>> --- a/sound/soc/codecs/cros_ec_codec.c
>>> +++ b/sound/soc/codecs/cros_ec_codec.c
>>> @@ -90,10 +90,17 @@ static int send_ec_host_command(struct cros_ec_device *ec_dev, uint32_t cmd,
>>>       if (outsize)
>>>               memcpy(msg->data, out, outsize);
>>>
>>> -     ret = cros_ec_cmd_xfer_status(ec_dev, msg);
>>> +     ret = cros_ec_cmd_xfer(ec_dev, msg);
>>>       if (ret < 0)
>>>               goto error;
>>>
>>> +     if (msg->result != EC_RES_SUCCESS) {
>>> +             dev_err(ec_dev->dev, "Command %d failed: %d\n", cmd,
>>> +                     msg->result);
>>> +             ret = -EPROTO;
>>> +             goto error;
>>> +     }
>>> +
>>>       if (insize)
>>>               memcpy(in, msg->data, insize);
>>>
>>>