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Date:   Mon, 6 Jul 2020 12:41:20 -0700
From:   Guenter Roeck <linux@roeck-us.net>
To:     Prashant Malani <pmalani@chromium.org>
Cc:     Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Benson Leung <bleung@chromium.org>,
        linux-kernel@vger.kernel.org, Yu-Hsuan Hsu <yuhsuan@chromium.org>
Subject: Re: [PATCH] platform/chrome: cros_ec_proto: Convert EC error codes
 to Linux error codes
Message-ID: <20200706194120.GB180826@roeck-us.net>
References: <20200704142607.171400-1-linux@roeck-us.net>
 <20200706185230.GA792857@google.com>
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On Mon, Jul 06, 2020 at 11:52:30AM -0700, Prashant Malani wrote:
> Hi Guenter,
> 
> On Sat, Jul 04, 2020 at 07:26:07AM -0700, Guenter Roeck wrote:
> > The EC reports a variety of error codes. Most of those, with the exception
> > of EC_RES_INVALID_VERSION, are converted to -EPROTO. As result, the actual
> > error code gets lost. Convert all EC errors to Linux error codes to report
> > a more meaningful error to the caller to aid debugging.
> > 
> > Cc: Yu-Hsuan Hsu <yuhsuan@chromium.org>
> > Cc: Prashant Malani <pmalani@chromium.org>
> > Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> > ---
> >  drivers/platform/chrome/cros_ec_proto.c | 37 +++++++++++++++++++------
> >  1 file changed, 29 insertions(+), 8 deletions(-)
> > 
> > diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> > index 3e745e0fe092..10aa9e483d35 100644
> > --- a/drivers/platform/chrome/cros_ec_proto.c
> > +++ b/drivers/platform/chrome/cros_ec_proto.c
> > @@ -543,6 +543,29 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
> >  }
> >  EXPORT_SYMBOL(cros_ec_cmd_xfer);
> >  
> > +static const int cros_ec_error_map[] = {
> > +	[EC_RES_INVALID_COMMAND] = -EOPNOTSUPP,
> > +	[EC_RES_ERROR] = -EIO,
> > +	[EC_RES_INVALID_PARAM] = -EINVAL,
> > +	[EC_RES_ACCESS_DENIED] = -EACCES,
> > +	[EC_RES_INVALID_RESPONSE] = -EPROTO,
> > +	[EC_RES_INVALID_VERSION] = -ENOTSUPP,
> > +	[EC_RES_INVALID_CHECKSUM] = -EBADMSG,
> > +	[EC_RES_IN_PROGRESS] = -EINPROGRESS,
> > +	[EC_RES_UNAVAILABLE] = -ENODATA,
> > +	[EC_RES_TIMEOUT] = -ETIMEDOUT,
> > +	[EC_RES_OVERFLOW] = -EOVERFLOW,
> > +	[EC_RES_INVALID_HEADER] = -EBADR,
> > +	[EC_RES_REQUEST_TRUNCATED] = -EBADR,
> > +	[EC_RES_RESPONSE_TOO_BIG] = -EFBIG,
> > +	[EC_RES_BUS_ERROR] = -EFAULT,
> > +	[EC_RES_BUSY] = -EBUSY,
> > +	[EC_RES_INVALID_HEADER_VERSION] = -EBADMSG,
> > +	[EC_RES_INVALID_HEADER_CRC] = -EBADMSG,
> > +	[EC_RES_INVALID_DATA_CRC] = -EBADMSG,
> > +	[EC_RES_DUP_UNAVAILABLE] = -ENODATA,
> > +};
> > +
> >  /**
> >   * cros_ec_cmd_xfer_status() - Send a command to the ChromeOS EC.
> >   * @ec_dev: EC device.
> > @@ -555,8 +578,7 @@ EXPORT_SYMBOL(cros_ec_cmd_xfer);
> >   *
> >   * Return:
> >   * >=0 - The number of bytes transferred
> > - * -ENOTSUPP - Operation not supported
> > - * -EPROTO - Protocol error
> > + * <0 - Linux error code
> >   */
> >  int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
> >  			    struct cros_ec_command *msg)
> > @@ -566,13 +588,12 @@ int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
> >  	ret = cros_ec_cmd_xfer(ec_dev, msg);
> >  	if (ret < 0) {
> >  		dev_err(ec_dev->dev, "Command xfer error (err:%d)\n", ret);
> > -	} else if (msg->result == EC_RES_INVALID_VERSION) {
> > -		dev_dbg(ec_dev->dev, "Command invalid version (err:%d)\n",
> > -			msg->result);
> > -		return -ENOTSUPP;
> >  	} else if (msg->result != EC_RES_SUCCESS) {
> > -		dev_dbg(ec_dev->dev, "Command result (err: %d)\n", msg->result);
> > -		return -EPROTO;
> > +		if (msg->result < ARRAY_SIZE(cros_ec_error_map) && cros_ec_error_map[msg->result])
> 
> Do we expect a case where cros_ec_error_map[msg->result] == 0?
> 

It seemed to be prudent to assume that this code is not going to be
updated whenever a new EC error code is added. Doing nothing would
risk returning 0, and addding WARN_ON or dev_warn seemed excessive.
Having said that, I don't really have a strong opinion one way
or another, and I'll be happy to change the code to whatever people
think is appropriate.

Thanks,
Guenter