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

[Michael Walle]

Am 2020-06-05 10:14, schrieb Andy Shevchenko:
> On Fri, Jun 5, 2020 at 12:14 AM Michael Walle <michael@xxxxxxxx> 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