linux-kernel - Re: [PATCH v4 04/11] watchdog: add support for sl28cpld watchdog

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Date:   Fri, 05 Jun 2020 12:24:54 +0200
From:   Michael Walle <michael@...le.cc>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-hwmon@...r.kernel.org, linux-pwm@...r.kernel.org,
        linux-watchdog@...r.kernel.org,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Lee Jones <lee.jones@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Shawn Guo <shawnguo@...nel.org>, Li Yang <leoyang.li@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <maz@...nel.org>, Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: Re: [PATCH v4 04/11] watchdog: add support for sl28cpld watchdog

Am 2020-06-05 10:14, schrieb Andy Shevchenko:
> On Fri, Jun 5, 2020 at 12:14 AM Michael Walle <michael@...le.cc> wrote:
>> 
>> Add support for the watchdog of the sl28cpld board management
>> controller. This is part of a multi-function device driver.
> 
> ...
> 
>> +#include <linux/of_device.h>
> 
> Didn't find a user of this.

I guess mod_devicetable.h then.

> 
> ...
> 
>> +static bool nowayout = WATCHDOG_NOWAYOUT;
>> +module_param(nowayout, bool, 0);
>> +MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started 
>> (default="
>> +                               __MODULE_STRING(WATCHDOG_NOWAYOUT) 
>> ")");
>> +
>> +static int timeout;
>> +module_param(timeout, int, 0);
>> +MODULE_PARM_DESC(timeout, "Initial watchdog timeout in seconds");
> 
> Guenter ACKed this, but I'm wondering why we still need module 
> parameters...

How would a user change the nowayout or the timeout? For the latter 
there is
a device tree entry, but thats not easy changable by the user.

> 
> ...
> 
>> +       int ret;
>> +
>> +       ret = regmap_read(wdt->regmap, wdt->offset + WDT_COUNT, &val);
>> +
>> +       return (ret < 0) ? 0 : val;
> 
> Besides extra parentheses and questionable ' < 0' part, the following
> would look better I think
> 
> ret = ...
> if (ret)
>   return 0;
> 
> return val;

yes, you're right.

> 
> ...
> 
>> +       int ret;
>> +
>> +       ret = regmap_write(wdt->regmap, wdt->offset + WDT_TIMEOUT, 
>> timeout);
>> +       if (!ret)
>> +               wdd->timeout = timeout;
>> +
>> +       return ret;
> 
> Similar story here:
> 
> ret = ...
> if (ret)
>   return ret;
> 
> wdd->... = ...
> return 0;
> 
> ...

ok

> 
>> +       ret = regmap_read(wdt->regmap, wdt->offset + WDT_CTRL, 
>> &status);
> 
>> +       if (ret < 0)
> 
> What ' < 0' means? Do we have some positive return values?
> Ditto for all your code.

probably not, I'll go over all return values and change them.

>> +               return ret;
> 
> ...
> 
>> +       if (status & WDT_CTRL_EN) {
>> +               sl28cpld_wdt_start(wdd);
> 
>> +               set_bit(WDOG_HW_RUNNING, &wdd->status);
> 
> Do you need atomic op here? Why?

I'd say consistency, all watchdog drivers do it like that. I just
had a look at where this is used, but it looks like access from
userspace is protected by a lock.

> 
>> +       }
> 
> ...
> 
>> +static const struct of_device_id sl28cpld_wdt_of_match[] = {
>> +       { .compatible = "kontron,sl28cpld-wdt" },
> 
>> +       {},
> 
> No comma.

yeah ;)

-- 
-michael