Re: [PATCH v3] gpiolib: match secondary fwnode too in gpio_device_find_by_fwnode()

[Rafael J. Wysocki]

On Wed, Feb 25, 2026 at 1:36 PM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
>
> On Wed, Feb 25, 2026 at 11:12 AM Bartosz Golaszewski
> <bartosz.golaszewski@xxxxxxxxxxxxxxxx> wrote:
> >
> > In GPIOLIB, during fwnode lookup, after having resolved the consumer's
> > reference to a specific fwnode, we only match it against the primary
> > node of the controllers. Let's extend that to also the secondary node by
> > reworking gpio_chip_match_by_fwnode()
> >
> > Suggested-by: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
> > Reviewed-by: Danilo Krummrich <dakr@xxxxxxxxxx>
> > Reviewed-by: Rafael J. Wysocki (Intel) <rafael@xxxxxxxxxx>
> > Reviewed-by: Linus Walleij <linusw@xxxxxxxxxx>
> > Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> > ---
> > Link: https://lore.kernel.org/all/aZUIFiOYt6GOlDQx@xxxxxxxxxx/
> > ---
> > Changes in v3:
> > - Remove the controversial patch 1/2 in favor of hand-coding its
> >   functionality in patch 2/2
> > - Link to v2: https://patch.msgid.link/20260223-device-match-secondary-fwnode-v2-0-966c00c9eeeb@xxxxxxxxxxxxxxxx
> >
> > Changes in v2:
> > - Fold the code initially put into driver code into GPIOLIB as advised
> >   by Rafael
> > - Rework the logic as suggested by Andy
> > - To that end: make fwnode_is_primary() public
> > - Link to v1: https://patch.msgid.link/20260219-device-match-secondary-fwnode-v1-0-a64e8d4754bc@xxxxxxxxxxxxxxxx
> > ---
> >  drivers/gpio/gpiolib.c | 12 +++++++++++-
> >  1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> > index c52200eaaaff82b12f22dd1ee8459bdd8ec10d81..0182603de368f2125baf174fcf5f1e893917c154 100644
> > --- a/drivers/gpio/gpiolib.c
> > +++ b/drivers/gpio/gpiolib.c
> > @@ -11,6 +11,7 @@
> >  #include <linux/errno.h>
> >  #include <linux/file.h>
> >  #include <linux/fs.h>
> > +#include <linux/fwnode.h>
> >  #include <linux/idr.h>
> >  #include <linux/interrupt.h>
> >  #include <linux/irq.h>
> > @@ -1395,7 +1396,16 @@ EXPORT_SYMBOL_GPL(gpio_device_find_by_label);
> >
> >  static int gpio_chip_match_by_fwnode(struct gpio_chip *gc, const void *fwnode)
> >  {
> > -       return device_match_fwnode(&gc->gpiodev->dev, fwnode);
> > +       struct device *dev = &gc->gpiodev->dev;
> > +       struct fwnode_handle *node = dev_fwnode(dev);
> > +
> > +       if (IS_ERR(fwnode))
> > +               return 0;
> > +
> > +       if (device_match_fwnode(dev, fwnode))
> > +               return 1;
> > +
> > +       return node && !IS_ERR(node->secondary) && node->secondary == fwnode;
>
> The second check is redundant because fwnode cannot be an error
> pointer (it has been checked against that already above) and so if
> node->secondary == fwnode, then node->secondary is not an error
> pointer.
>
> I'm not sure if fwnode can be NULL here, but if it can, it should be
> checked against NULL.  Alternatively, node->secondary can be checked
> against NULL and compared to fwnode.
>
> So, if fwnode != NULL cannot be guaranteed,
>
>         return fwnode && node && node->secondary == fwnode;
>
> or
>
>         return node && node->secondary && node->secondary == fwnode;
>
> The overhead of the former may be a bit lower because it avoids
> dereferencing node when fwnode is NULL, but the compiler should be
> able to optimize this anyway.

Or even the device_match_fwnode() check can be folded into the last line:

static int gpio_chip_match_by_fwnode(struct gpio_chip *gc, const void *fwnode)
 {
-       return device_match_fwnode(&gc->gpiodev->dev, fwnode);
+       struct device *dev = &gc->gpiodev->dev;
+       struct fwnode_handle *node = dev_fwnode(dev);
+
+       if (IS_ERR_OR_NULL(fwnode))
+               return 0;
+
+       return node == fwnode || (node && node->secondary == fwnode);
 }