On Tue, Mar 17, 2020 at 10:30:56PM +0100, Uwe Kleine-König wrote: > Hello Thierry, > > On Tue, Mar 17, 2020 at 06:43:44PM +0100, Thierry Reding wrote: > > On Tue, Mar 17, 2020 at 02:32:26PM +0200, Oleksandr Suvorov wrote: > > > Add the description of PWM_POLARITY_NORMAL flag. > > > > > > Signed-off-by: Oleksandr Suvorov <oleksandr.suvorov@xxxxxxxxxxx> > > > --- > > > > > > Documentation/devicetree/bindings/pwm/pwm.txt | 1 + > > > 1 file changed, 1 insertion(+) > > > > > > diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt > > > index 084886bd721e..440c6b9a6a4e 100644 > > > --- a/Documentation/devicetree/bindings/pwm/pwm.txt > > > +++ b/Documentation/devicetree/bindings/pwm/pwm.txt > > > @@ -46,6 +46,7 @@ period in nanoseconds. > > > Optionally, the pwm-specifier can encode a number of flags (defined in > > > <dt-bindings/pwm/pwm.h>) in a third cell: > > > - PWM_POLARITY_INVERTED: invert the PWM signal polarity > > > +- PWM_POLARITY_NORMAL: don't invert the PWM signal polarity > > > > This doesn't make sense. PWM_POLARITY_NORMAL is not part of the DT ABI. > > "is not part of the DT ABI" is hardly a good reason. If it's sensible to > be used, it is sensible to define it. That's exactly it. It's not sensible at all to use it. If you define it here it means people are allowed to do stuff like this: pwms = <&pwm 1234 PWM_POLARITY_INVERTED | PWM_POLARITY_NORMAL>; which doesn't make sense. What's more, it impossible for the code to even notice that you're being silly because | PWM_POLARITY_NORMAL is just | 0 and that's just a nop. > (And as far as I understand it, the term PWM_POLARITY_INVERTED isn't > part of the DT ABI either. Only the value 1 has a meaning (for some PWM > controlers).) > > > The third cell of the specifier is a bitmask of flags. > > > > PWM_POLARITY_NORMAL is an enumeration value that evaluates to 0, so it > > makes absolutely no sense as a flag. > > Using 0 or PWM_POLARITY_NORMAL doesn't have an effect on the compiled > device tree, that's true. But having the term PWM_POLARITY_NORMAL (in > contrast to a plain 0) in a dts file is useful in my eyes for human > readers. > > > PWM signals are considered to be "normal" by default, so no flag is > > necessary to specify that. > > GPIOs are considered to be active high by default, still there is > GPIO_ACTIVE_HIGH (which also evaluates to 0). Also there is > IRQ_TYPE_NONE. I'm aware of those. That doesn't mean that everything needs to have symbolic names. Thierry
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