Re: [PATCH] gpiolib: use of_node_name if line-name is missing

[Frank Wunderlich (linux)]

Am 2026-09-17 15:00, schrieb Andy Shevchenko:
> On Thu, Sep 17, 2026 at 02:28:13PM +0200, Frank Wunderlich wrote:
>
> > Until v7.0, GPIO hogs inherited the DT node name when no line-name
> > property was specified. This was implemented as a fallback in
> > of_parse_own_gpio().
> >
> > Commit d1d564ec4992 ("gpio: move hogs into GPIO core") moved hog 
> > parsing
> > into the GPIO core and removed this fallback.
> >
> > Consequently, GPIO hogs without a line-name property are now displayed
> > with a ? in /sys/kernel/debug/gpio. Restore the old fallback.
>
> ...
>
> > int gpiochip_add_hog(struct gpio_chip *gc, struct fwnode_handle 
> > *fwnode)
>
> >  	fwnode_property_read_string(fwnode, "line-name", &name);
> >
> > +	if (!name && is_of_node(fwnode))
> > +		name = to_of_node(fwnode)->name;
>
> Can we move it inside the loop? Yes, I understand that it will be 
> unnecessarily
> called more times than required, but gpiod_hog() is called anyway in 
> the loop,
> so I don't think it will be a big deal. With that it will allow to 
> group
> OF-specific code in one location.
>
> >  	for (unsigned int i = 0; i < num_hogs; i++) {
> >  		if (is_of_node(fwnode)) {
>
> 		...somewhere inside this conditional...
>
> >  			/*

I'm not sure what you want to achieve here (maybe only to have the 
is_of_node-condition once?, as the loop imho is only for enumerating 
multiple gpio (like "gpios = <3 0>, <4 0>;") inside one hog of_node. 
Here the node-name will never change (like the line-name above) and 
read-once is correct.
But while looking at the code i also thought about these multi-gpio-hogs 
(label and output-X). Imho here something like the gpio-controllers 
"line-names" would make sense as well as something similar for the 
output (or just handling this with the GPIO_ACTIVE_HIGH/LOW param).

But if you think the part should be moved into the loop, that's no big 
deal.

regards Frank