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Date:   Thu, 11 Apr 2019 17:40:12 +0200
From:   Enric Balletbo Serra <eballetbo@...il.com>
To:     Guenter Roeck <groeck@...gle.com>
Cc:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        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

Hi,

Missatge de Guenter Roeck <groeck@...gle.com> del dia dc., 3 d’abr.
2019 a les 18:27:
>
> 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.
> >

Actually, I discarded this patch, I assumed wrongly that this patch
will avoid some boilerplate on the above cases but that's not true
because there is no difference between check that ret == -EINVAL or
check that msg->result == EC_RES_INVALID_COMMAND.

> > While here, also document properly the cros_ec_cmd_xfer_status
> > function.
> >

Also, this function was properly documented in the header, so that is
not needed, my bad.

Thanks,
 Enric

> > 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
> >

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