linux-kernel - Re: [PATCH] platform/chrome: cros_ec_proto: Also return invalid command in cros_ec_cmd_xfer

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Message-ID: <CABXOdTe3sYq2bKPEajHu9LzMLXhEbABQAAGc8OfcYU3Z9LY7xQ@mail.gmail.com>
Date:   Wed, 3 Apr 2019 09:25:04 -0700
From:   Guenter Roeck <groeck@...gle.com>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Guenter Roeck <groeck@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Gwendal Grignou <gwendal@...omium.org>, kernel@...labora.com,
        Dmitry Torokhov <dtor@...omium.org>
Subject: Re: [PATCH] platform/chrome: cros_ec_proto: Also return invalid
 command in cros_ec_cmd_xfer_status

On Wed, Apr 3, 2019 at 6:51 AM Enric Balletbo i Serra
<enric.balletbo@...labora.com> wrote:
>
> The commit 9798ac6d32c1 ("mfd: cros_ec: Add cros_ec_cmd_xfer_status()
> helper") was introduced to remove duplicated code in several users of
> the cros_ec_cmd_xfer function. The idea behind that commit is mask all
> the EC errors as protocol error when the EC command fails, what is
> really useful because as a user you probably don't care of the exact
> error reported by the EC, you only want to know if the command succeeded
> or not.
>
> That works for most of the errors returned by the EC, but we might be
> also interested on report the EC_RES_INVALID_COMMAND, which happens when
> the command is not supported by the EC. An use case for this is when you
> need to show/hide a sysfs attribute for a specific command and you don't
> have a EC feature flag that tells you that the command is supported or
> not.
>
> While here, also document properly the cros_ec_cmd_xfer_status
> function.
>
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>

Reviewed-by: Guenter Roeck <groeck@...omium.org>

> ---
>
>  drivers/platform/chrome/cros_ec_proto.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
> index 97a068dff192..a4e0d3a6d891 100644
> --- a/drivers/platform/chrome/cros_ec_proto.c
> +++ b/drivers/platform/chrome/cros_ec_proto.c
> @@ -478,6 +478,16 @@ int cros_ec_cmd_xfer(struct cros_ec_device *ec_dev,
>  }
>  EXPORT_SYMBOL(cros_ec_cmd_xfer);
>
> +/**
> + * cros_ec_cmd_xfer_status() - Send EC command.
> + * @ec_dev: EC device.
> + * @msg: EC message data for request and response.
> + *
> + * Return:
> + * 0 - OK
> + * -EINVAL - Invalid command.
> + * -EPROTO - Protocol error.
> + */
>  int cros_ec_cmd_xfer_status(struct cros_ec_device *ec_dev,
>                             struct cros_ec_command *msg)
>  {
> @@ -486,6 +496,11 @@ 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_COMMAND) {
> +               dev_dbg(ec_dev->dev,
> +                       "Command %d not supported for this device\n",
> +                       msg->command);
> +               return -EINVAL;
>         } else if (msg->result != EC_RES_SUCCESS) {
>                 dev_dbg(ec_dev->dev, "Command result (err: %d)\n", msg->result);
>                 return -EPROTO;
> --
> 2.20.1
>