leds: core: Report ENODATA for brightness of hardware controlled LED

While the LED is controlled fully by the hardware, the value cached by
the LED driver core is incorrect. Return ENODATA to userspace in this
case.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Link: https://patch.msgid.link/20260521-cros_ec-leds-hw-trigger-brightness-v1-1-6cd9d7c9671e@weissschuh.net
Signed-off-by: Lee Jones <lee@kernel.org>

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index a17db3d6644f5d62a9a4606ff28ea19a9a3190fb..a51b0ed5388644e41c2050eabf528ac1da7401e6 100644 (file)
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -27,12 +27,25 @@ static LIST_HEAD(leds_lookup_list);
 
 static struct workqueue_struct *leds_wq;
 
+static bool led_trigger_is_hw_controlled(struct led_classdev *led_cdev)
+{
+#ifdef CONFIG_LEDS_TRIGGERS
+       guard(rwsem_read)(&led_cdev->trigger_lock);
+       return led_cdev->trigger && led_cdev->trigger->trigger_type;
+#else
+       return false;
+#endif
+}
+
 static ssize_t brightness_show(struct device *dev,
                struct device_attribute *attr, char *buf)
 {
        struct led_classdev *led_cdev = dev_get_drvdata(dev);
        unsigned int brightness;
 
+       if (led_trigger_is_hw_controlled(led_cdev))
+               return -ENODATA;
+
        mutex_lock(&led_cdev->led_access);
        led_update_brightness(led_cdev);
        brightness = led_cdev->brightness;