gpio: shared: verify con_id when adding proxy lookup

When matching the firmware node with the potential consumer, we
currently omit the con_id string. This can lead to false positives in
the unlikely case of the consumer having been assigned more than one
shared GPIO. Check the connector ID before proceeding.

Fixes: a060b8c ("gpiolib: implement low-level, shared GPIO support")
Link: https://lore.kernel.org/r/20251222-gpio-shared-reset-gpio-proxy-v1-2-8d4bba7d8c14@oss.qualcomm.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

Author: Bartosz Golaszewski

drivers/gpio/gpiolib-shared.c

@@ -365,7 +365,8 @@ static bool gpio_shared_dev_is_reset_gpio(struct device *consumer,
 }
 #endif /* CONFIG_RESET_GPIO */
 
-int gpio_shared_add_proxy_lookup(struct device *consumer, unsigned long lflags)
+int gpio_shared_add_proxy_lookup(struct device *consumer, const char *con_id,
+				 unsigned long lflags)
 {
 	const char *dev_id = dev_name(consumer);
 	struct gpio_shared_entry *entry;
@@ -384,6 +385,10 @@ int gpio_shared_add_proxy_lookup(struct device *consumer, unsigned long lflags)
 
 			guard(mutex)(&ref->lock);
 
+			if ((!con_id && ref->con_id) || (con_id && !ref->con_id) ||
+			    (con_id && ref->con_id && strcmp(con_id, ref->con_id) != 0))
+				continue;
+
 			/* We've already done that on a previous request. */
 			if (ref->lookup)
 				return 0;

drivers/gpio/gpiolib-shared.h

@@ -16,7 +16,8 @@ struct device;
 
 int gpio_device_setup_shared(struct gpio_device *gdev);
 void gpio_device_teardown_shared(struct gpio_device *gdev);
-int gpio_shared_add_proxy_lookup(struct device *consumer, unsigned long lflags);
+int gpio_shared_add_proxy_lookup(struct device *consumer, const char *con_id,
+				 unsigned long lflags);
 
 #else
 
@@ -28,6 +29,7 @@ static inline int gpio_device_setup_shared(struct gpio_device *gdev)
 static inline void gpio_device_teardown_shared(struct gpio_device *gdev) { }
 
 static inline int gpio_shared_add_proxy_lookup(struct device *consumer,
+					       const char *con_id,
 					       unsigned long lflags)
 {
 	return 0;

drivers/gpio/gpiolib.c

@@ -4717,7 +4717,8 @@ struct gpio_desc *gpiod_find_and_request(struct device *consumer,
 			 * lookup table for the proxy device as previously
 			 * we only knew the consumer's fwnode.
 			 */
-			ret = gpio_shared_add_proxy_lookup(consumer, lookupflags);
+			ret = gpio_shared_add_proxy_lookup(consumer, con_id,
+							   lookupflags);
 			if (ret)
 				return ERR_PTR(ret);