On Sun, Jul 26, 2020 at 03:00:59PM -0700, Guenter Roeck wrote:
> Since commit c5cd2b47b203 ("platform/chrome: cros_ec_proto: Report command
> not supported") we can no longer assume that cros_ec_cmd_xfer_status()
> reports -EPROTO for all errors returned by the EC itself. A follow-up
> patch will change cros_ec_cmd_xfer_status() to report additional errors
> reported by the EC as distinguished Linux error codes.
> 
> Handle this change by no longer assuming that only -EPROTO is used
> to report all errors returned by the EC itself. Instead, support both
> the old and the new error codes.
> 
> Cc: Gwendal Grignou <[email protected]>
> Cc: Yu-Hsuan Hsu <[email protected]>
> Cc: Prashant Malani <[email protected]>
> Cc: Brian Norris <[email protected]>
> Signed-off-by: Guenter Roeck <[email protected]>
> ---
> v3: Added patch
> 
>  drivers/pwm/pwm-cros-ec.c | 21 ++++++++++++++-------
>  1 file changed, 14 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pwm/pwm-cros-ec.c b/drivers/pwm/pwm-cros-ec.c
> index 09c08dee099e..ef05fba1bd37 100644
> --- a/drivers/pwm/pwm-cros-ec.c
> +++ b/drivers/pwm/pwm-cros-ec.c
> @@ -213,20 +213,27 @@ static int cros_ec_num_pwms(struct cros_ec_device *ec)
>               u32 result = 0;
>  
>               ret = __cros_ec_pwm_get_duty(ec, i, &result);
> -             /* We want to parse EC protocol errors */
> -             if (ret < 0 && !(ret == -EPROTO && result))
> -                     return ret;
> -
>               /*
>                * We look for SUCCESS, INVALID_COMMAND, or INVALID_PARAM
>                * responses; everything else is treated as an error.
>                */

This comment is at least misleading now.

> -             if (result == EC_RES_INVALID_COMMAND)
> +             switch (ret) {
> +             case -EOPNOTSUPP:       /* invalid command */
>                       return -ENODEV;

My first reaction here was to wonder why -EOPNOTSUPP isn't passed to the
upper layer. OK, this is a loop to test the number of available devices.

> -             else if (result == EC_RES_INVALID_PARAM)
> +             case -EINVAL:           /* invalid parameter */
>                       return i;
> -             else if (result)
> +             case -EPROTO:
> +                     /* Old or new error return code: Handle both */
> +                     if (result == EC_RES_INVALID_COMMAND)
> +                             return -ENODEV;
> +                     else if (result == EC_RES_INVALID_PARAM)
> +                             return i;

If I understand correctly this surprising calling convention (output
parameter is filled even though the function returned an error) is the
old one that is to be fixed.

>                       return -EPROTO;
> +             default:
> +                     if (ret < 0)
> +                             return ret;
> +                     break;
> +             }
>       }
>  

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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