Re: [PATCH 4/4] watchdog: st_wdt: Add new driver for ST's LPC Watchdog

[Guenter Roeck]

On 09/08/2014 05:32 AM, Lee Jones wrote:
> On Fri, 05 Sep 2014, Guenter Roeck wrote:
...
> > > +
> > > +static struct st_wdog_syscfg stid127_syscfg = {
> > > +	.type_mask	= BIT(2),
> > > +	.enable_mask	= BIT(2),
> > > +};
> > > +
> > > +static struct st_wdog_syscfg stih415_syscfg = {
> > > +	.type_mask	= BIT(6),
> > > +	.enable_mask	= BIT(7),
> > > +};
> > > +
> > > +static struct st_wdog_syscfg stih416_syscfg = {
> > > +	.type_mask	= BIT(6),
> > > +	.enable_mask	= BIT(7),
> > > +};
> > > +
> > > +static struct st_wdog_syscfg stih407_syscfg = {
> > > +	.enable_mask	= BIT(19),
> > > +};
> > > +
...

> > > +	/* Mask/unmask watchdog reset */
> > > +	regmap_update_bits(st_wdog->syscfg->regmap,
> > > +			   st_wdog->syscfg->enable_reg,
> > > +			   st_wdog->syscfg->enable_mask,
> > > +			   !enable);
> >
> > enable is a bool, but is supposed to provide the value to be put into the
> > register, masked with enable_mask. Unless I am missing something, the value
> > is not shifted in regmap_update_bits. So I don't think this can work, but
> > effectively always writes zero into the mask unless the mask happens to be
> > at bit position 0 - which never happens.
> >
> > Same is true for warm_reset above, which also has values 0 or 1.
> >
> > I know it does not really matter in C (at least when it comes to handling
> > 0 and 1), but I would suggest to avoid mixing booleans with bit masks.
>
> You're right of course, great spot.
>
> How about?
>
>    !enable << ffs(st_wdog->syscfg->enable_mask).
Seems to add a lot of complexity (as in 'makes it difficult to understand')
to avoid a conditional, and assumes that enable_mask will never have more
than one bit set. I would go with
	enable ? st_wdog->syscfg->enable_mask : 0
to avoid confusion, but your call.

Guenter

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