[PATCH v2 03/22] pinctrl: pinctrl-generic: Make the "function" property optional

[Changhuang Liang]

Hi, Conor

Thanks for the comments.

> On Fri, May 15, 2026 at 05:55:48AM +0000, Changhuang Liang wrote:
> > Hi, Conor
> >
> > Thanks for the review.
> >
> > > On Thu, May 14, 2026 at 04:11:59AM -0700, Changhuang Liang wrote:
> > > > Some pinctrl subnodes only need to configure pin properties (e.g.,
> > > > power-source, bias, drive strength) without assigning any mux function.
> > > >
> > > > Currently, the driver requires a valid "function" property for all
> > > > pinctrl subnodes. This forces the addition of dummy or redundant
> > > > "function" entries when only pin configuration is needed.
> > > >
> > > > Example use case:
> > > > gpios-configs {
> > > >     config {
> > > >         pins = <0 1 2 3>;
> > > >         power-source = <0>;
> > > >     };
> > > > };
> > > >
> > > > Make the "function" property optional. If it is missing, skip
> > > > adding the mux map and only process the pin configuration.
> > >
> > > I looked through the series though and all controllers appear to
> > > have pins and functions, is it the case that gpio is the default for
> > > these pins, so you are omitting the functions property when you are using
> the pin in gpio mode?
> > > Saying that the functions property is "redudant" makes it seem like
> > > this might be the case?
> > >
> > > I've got some feedback here, but I can't really provide it without
> > > knowing the answer to that question.
> >
> >
> > "From v1, copying Linus's suggestion:
> >
> > > +  This domain contains 4 IO groups which support voltage levels
> > > + 1.8V and 3.3V  gpioe-spi - comprises PAD_GPIO_C0 through
> PAD_GPIO_C4.
> > > +  gpioe-qspi0 - comprises PAD_GPIO_C5 through PAD_GPIO_C11.
> > > +  gpioe-qspi1 - comprises PAD_GPIO_C12 through PAD_GPIO_C19.
> > > +  gpioe-qspi2 - comprises PAD_GPIO_C20 through PAD_GPIO_C27.
> > > +
> > > +  Each of the above IO groups must be configured with a voltage
> > > + setting that matches the external  voltage level provided to the IO
> group.
> >
> > So your hardware has groups and support some properties on the group
> level.
> >
> > So expose these groups and make these properties configurable per
> > group instead of inventing per-group properties.
> >
> > > +  gpioe-spi-vref:
> > > +  gpioe-qspi0-vref:
> > > +  gpioe-qspi1-vref:
> > > +  gpioe-qspi2-vref:
> >
> > Create proper groups in the pin controller then use the standard
> > pincfg property power-source = <...>; for this.
> >
> > Example for a simple default hog:
> >
> > pinctrl {
> >     /* Hog the QSPI pins */
> >     pinctrl-names = "default";
> >     pinctrl-0 = <&qspi_default>;
> >
> >     qspi_default: pinctrl-qspi {
> >         config {
> >             groups = "gpioe-qspi-pins";
> >             power-source = <2>;
> >         };
> >     };
> > };
> >
> > The groups can be orthogonal to other pin handling, that's fine.
> > Implement .pin_config_group_set in struct pinconf_ops.
> >
> > However, I found that pinctrl_generic_pins_function_dt_node_to_map()
> > does not handle the groups property,
> 
> That's kind of the whole point of the function, see the comment about
> it:
> /*
>  * For platforms that do not define groups or functions in the driver, but
>  * instead use the devicetree to describe them. This function will, unlike
>  * pinconf_generic_dt_node_to_map() etc which rely on driver defined
> groups
>  * and functions, create them in addition to parsing pinconf properties and
>  * adding mappings.
>  */
> 
> If you have the groups property in your devicetree, it contains strings that the
> driver uses to match against the groups it has defined in it.
> See my recently added microchip,pic64gx-pinctrl-gpio2 for an example of that
> if you like.
> 
> However, if you are using the pins or pinmux properties, the groups are not
> defined in the driver, and need to be created at runtime. That's what
> pinctrl_generic_pins_function_dt_node_to_map() is for - it creates the groups
> at runtime when using the *pins* and *function* properties.
> It's in the name!
> 
> Judging by your drivers, and how many structures you have that look very like
> groups from a quick glance, probably you can still make use of the groups
> property. The equivalent function to
> pinctrl_generic_pins_function_dt_node_to_map() when you're using driver
> defined groups is pinconf_generic_dt_node_to_map().

I feel that for the current platform, initializing pin voltage is suitable for using `pinconf_generic_dt_node_to_map()`, 
and configuring pin mux is suitable for using `pinctrl_generic_pins_function_dt_node_to_map()`. Should I use both 
of them at the same time?

> 
> Also, I notice that you never actually answered the question that I
> asked:
> > > I looked through the series though and all controllers appear to
> > > have pins and functions, is it the case that gpio is the default for
> > > these pins, so you are omitting the functions property when you are using
> the pin in gpio mode?
> > > Saying that the functions property is "redudant" makes it seem like
> > > this might be the case?
> 
> Are you omitting the functions property from your nodes when they're using
> gpio because it is a default, or is there some other reason why you're omitting
> the functions property sometimes?

Sorry, I missed that question. What I meant by making 'functions' optional is that I 
don't care whether the current pin's default value is GPIO or some other function. 
Here, I just want to initialize the default voltage of these pins, not configure their 
pin function.

This part of the voltage configuration only has one register, but it applies to many 
pins, so currently it seems I can only use pinctrl hog to initialize it.

Best Regards,
Changhuang

> 
> > currently, my node uses pins instead, so it looks like this:
> >
> > +&pinctrl_per3 {
> > +	pinctrl-names = "default";
> > +	pinctrl-0 = <&gpios_configs>;
> > +
> > +	gpios_configs: gpios-hog-grp {
> > +		gpios-hog-pins {
> > +			pins = <PADNUM_PER3_GPIO_E0
> > +				PADNUM_PER3_GPIO_E1
> > +				PADNUM_PER3_GPIO_E2
> > +				PADNUM_PER3_GPIO_E3
> > +				PADNUM_PER3_GPIO_E4
> > +				PADNUM_PER3_GPIO_E5
> > +				PADNUM_PER3_GPIO_E6
> > +				PADNUM_PER3_GPIO_E7
> > +				PADNUM_PER3_GPIO_E8
> > +				PADNUM_PER3_GPIO_E9
> > +				PADNUM_PER3_GPIO_E10>;
> > +			power-source = <JHB100_PINVREF_1_8V>;
> > +		};
> > +	};
> > +};
> >
> > Best regards,
> > Changhuang
> >