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Date:   Thu, 20 Feb 2020 07:52:00 -0800
From:   Guenter Roeck <linux@roeck-us.net>
To:     Evan Benn <evanbenn@chromium.org>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Julius Werner <jwerner@chromium.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Mauro Carvalho Chehab <mchehab+samsung@kernel.org>,
        Marcin Juszkiewicz <marcin.juszkiewicz@linaro.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Olof Johansson <olof@lixom.net>,
        Leonard Crestez <leonard.crestez@nxp.com>,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>,
        Dinh Nguyen <dinguyen@kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Will Deacon <will@kernel.org>, linux-watchdog@vger.kernel.org,
        Rob Herring <robh@kernel.org>,
        Wim Van Sebroeck <wim@linux-watchdog.org>,
        =?iso-8859-1?Q?Cl=E9ment_P=E9ron?= <peron.clem@gmail.com>,
        Shawn Guo <shawnguo@kernel.org>,
        "David S. Miller" <davem@davemloft.net>,
        Anson Huang <Anson.Huang@nxp.com>
Subject: Re: [PATCH 2/2] watchdog: Add new arm_smc_wdt watchdog driver
Message-ID: <20200220155159.GB29658@roeck-us.net>
References: <20200214062637.216209-1-evanbenn@chromium.org>
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On Thu, Feb 20, 2020 at 05:50:03PM +1100, Evan Benn wrote:
> > > +     if ((int)res->a0 == PSCI_RET_NOT_SUPPORTED)
> > > +             return -ENOTSUPP;
> >
> > -ENODEV would be better here.
> >
> > > +     if ((int)res->a0 == PSCI_RET_INVALID_PARAMS)
> > > +             return -EINVAL;
> > > +     if ((int)res->a0 < 0)
> > > +             return -EIO;
> 
> In fixing this I found drivers/firmware/psci/psci.c:145
> Which also translates psci codes to errno codes, but uses EOPNOTSUPP:
> 
>     switch (errno) {
>     case PSCI_RET_SUCCESS:
>         return 0;
>     case PSCI_RET_NOT_SUPPORTED:
>         return -EOPNOTSUPP;
>     case PSCI_RET_INVALID_PARAMS:
>     case PSCI_RET_INVALID_ADDRESS:
>         return -EINVAL;
>     case PSCI_RET_DENIED:
>         return -EPERM;
>     };
> 
>     return -EINVAL;
> 
> Are these more appropriate?
> 

It is customary for driver probe functions to return -ENODEV if the
device is not supported. I don't see a reason why this driver should
behave any different. "but this other driver does it" is never a good
argument.

Having said that, yet, with the exception of -EOPNOTSUPP the other
return values would be more appropriate.

Guenter