leds: spi-byte: Initialize device node before access

Commit 7f9ab862e05c ("leds: spi-byte: Call of_node_put() on error path") was merged in 6.11 and then backported to stable trees through 5.10. It relocates the line that initializes the variable 'child' to a later point in spi_byte_probe().

Versions < 6.9 do not have commit ccc35ff2fd29 ("leds: spi-byte: Use devm_led_classdev_register_ext()"), which removes a line that reads a property from 'child' before its new initialization point. Consequently, spi_byte_probe() reads from an uninitialized device node in stable kernels 6.6-5.10.

Initialize 'child' before it is first accessed.

---

As an alternative to moving the initialization of 'child' up, Fedor Pchelkin proposed [1] backporting the change that removes the intermediate access.

[1] https://lore.kernel.org/stable/[email protected]/

---
 drivers/leds/leds-spi-byte.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index afe9bff7c7c1..4520df1e2341 100644
@@ -96,6 +96,7 @@ static int spi_byte_probe(struct spi_device *spi)
 	if (!led)
 		return -ENOMEM;
 
+	child = of_get_next_available_child(dev_of_node(dev), NULL);
 	of_property_read_string(child, "label", &name);
 	strscpy(led->name, name, sizeof(led->name));
 	led->spi = spi;

@@ -106,7 +107,6 @@ static int spi_byte_probe(struct spi_device *spi)
 	led->ldev.max_brightness = led->cdef->max_value - led->cdef->off_value;
 	led->ldev.brightness_set_blocking = spi_byte_brightness_set_blocking;
 
-	child = of_get_next_available_child(dev_of_node(dev), NULL);
 	state = of_get_property(child, "default-state", NULL);
 	if (state) {
 		if (!strcmp(state, "on")) {

2.52.0.351.gbe84eed79e-goog