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

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

[Frank Wunderlich]

From: Frank Wunderlich <frank-w@public-files.de>

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.

Fixes: d1d564ec4992 ("gpio: move hogs into GPIO core")
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
---
 drivers/gpio/gpiolib.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index ef8ccaf17c9c..acf41cfbcf10 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1013,6 +1013,9 @@ 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;
+
 	for (unsigned int i = 0; i < num_hogs; i++) {
 		if (is_of_node(fwnode)) {
 			/*
-- 
2.53.0

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

[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...

>  			/*

-- 
With Best Regards,
Andy Shevchenko

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

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

[Andy Shevchenko]

On Thu, Sep 17, 2026 at 03:20:49PM +0200, Frank Wunderlich (linux) wrote:
> Am 2026-09-17 15:00, schrieb Andy Shevchenko:
> > On Thu, Sep 17, 2026 at 02:28:13PM +0200, Frank Wunderlich wrote:

...

> > > 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.

The primary goal is stop spreading OF-specific code. If you have noticed the
function was also rewritten (during the move) to be fwnode agnostic, but that
was not feasible by 100%, the leftover is collected inside the mentioned loop.
That's why I really prefer to keep all OF code there.

> 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.

Yes, I think that way.

-- 
With Best Regards,
Andy Shevchenko

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

[Andy Shevchenko]

On Thu, Sep 17, 2026 at 04:37:57PM +0300, Andy Shevchenko wrote:
> On Thu, Sep 17, 2026 at 03:20:49PM +0200, Frank Wunderlich (linux) wrote:
> > Am 2026-09-17 15:00, schrieb Andy Shevchenko:
> > > On Thu, Sep 17, 2026 at 02:28:13PM +0200, Frank Wunderlich wrote:

...

> > > > 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.
> 
> The primary goal is stop spreading OF-specific code. If you have noticed the
> function was also rewritten (during the move) to be fwnode agnostic, but that
> was not feasible by 100%, the leftover is collected inside the mentioned loop.
> That's why I really prefer to keep all OF code there.
> 
> > 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.
> 
> Yes, I think that way.

Btw, while doing that, also add a comment explaining why (like we have now for
the OF flag translations).

-- 
With Best Regards,
Andy Shevchenko