Re: [PATCH v3 07/11] watchdog: xilinx: Use of_property_read_u32

[Guenter Roeck]

On 02/22/2014 05:08 PM, Alejandro Cabrera wrote:
> On 22/2/2014 10:46 AM, Wim Van Sebroeck wrote:
> > Hi All,
> >
> > > Hi Michal,
> > >
> > > On Wed, Feb 12, 2014 at 02:41:21PM +0100, Michal Simek wrote:
> > > > Use of_property_read_u32 functions to clean probe function.
> > > >
> > > > Signed-off-by: Michal Simek<michal.simek@xxxxxxxxxx>
> > > > Reviewed-by: Guenter Roeck<linux@xxxxxxxxxxxx>
> > > > ---
> > > >
> > > > Changes in v3:
> > > > - Remove one if checking and use variable directly
> > > Looks good.
> > >
> > > Another comment/remark.
> > >
> > > > -    pfreq = (u32 *)of_get_property(pdev->dev.of_node,
> > > > -                    "clock-frequency", NULL);
> > > > -
> > > > -    if (pfreq == NULL) {
> > > > +    rc = of_property_read_u32(pdev->dev.of_node, "clock-frequency",&pfreq);
> > > > +    if (rc) {
> > > >           dev_warn(&pdev->dev,
> > > >                "The watchdog clock frequency cannot be obtained\n");
> > > >           no_timeout = true;
> > > >       }
> > > >
> > > > -    tmptr = (u32 *)of_get_property(pdev->dev.of_node,
> > > > -                    "xlnx,wdt-interval", NULL);
> > > > -    if (tmptr == NULL) {
> > > > +    rc = of_property_read_u32(pdev->dev.of_node, "xlnx,wdt-interval",
> > > > +                &xdev->wdt_interval);
> > > > +    if (rc) {
> > > >           dev_warn(&pdev->dev,
> > > >                "Parameter \"xlnx,wdt-interval\" not found\n");
> > > >           no_timeout = true;
> > > > -    } else {
> > > > -        xdev->wdt_interval = *tmptr;
> > > >       }
> > > >
> > > > -    tmptr = (u32 *)of_get_property(pdev->dev.of_node,
> > > > -                    "xlnx,wdt-enable-once", NULL);
> > > > -    if (tmptr == NULL) {
> > > > +    rc = of_property_read_u32(pdev->dev.of_node, "xlnx,wdt-enable-once",
> > > > +                &enable_once);
> > > > +    if (rc)
> > > >           dev_warn(&pdev->dev,
> > > >                "Parameter \"xlnx,wdt-enable-once\" not found\n");
> > > > -        watchdog_set_nowayout(xilinx_wdt_wdd, true);
> > > > -    }
> > > All the above properties are optional. Is a warning really
> > > warranted in this case ? I usually associate a warning with
> > > something that is wrong, which is not the case here.
> > >
> > > I would encourage you to drop those warnings, but that should be
> > > a separate patch.
> > I agree with Guenter: these are not really warnings. Seperate patch is thus welcome.
> Hi
>
> I support Michal intention, I think it is a warning because device tree blob must have the "xlnx,wdt-enable-once" property specified in order to allow the system to be sure of the real value of this property. In addition to, this warning can be helpful to detect a wrong device tree specification.

The dt documentation states that the properties are optional.

Optional properties:
- clock-frequency       : Frequency of clock in Hz
- xlnx,wdt-enable-once  : 0 - Watchdog can be restarted
                          1 - Watchdog can be enabled just once
- xlnx,wdt-interval     : Watchdog timeout interval in 2^<val> clock cycles,
                          <val> is integer from 8 to 31.

This clearly conflicts with your statement. An optional property
is just that, optional. If it warrants a warning, it must
not be optional. If you claim that not providing the properties
would be "wrong", why are they defined as optional ?
What is your definition of "wrong" and "must have" ?
How do you expect anyone to know that omitting those
"optional" properties is by some definition "wrong" ?

Guenter


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