Re: [PATCH] platform/chrome: cros_ec_proto: Convert EC error codes to Linux error codes

[Prashant Malani <pmalani@chromium.org>]

On Mon, Jul 6, 2020 at 12:41 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> 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 for providing the rationale. I think if a new EC error code is
added (and this array isn't updated),
msg->result < ARRAY_SIZE(cros_ec_error_map) would return false, and
the code block would return -EPROTO.

I'll defer to the maintainer's opinion(s), but I think we can remove
the condition after '&&'.

Best regards,

>
> Thanks,
> Guenter