Clarify the possible values of event id, rather than requiring the
reader to infer.

Signed-off-by: Kent Gibson <warthog618@gmail.com>
---
 include/uapi/linux/gpio.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/uapi/linux/gpio.h b/include/uapi/linux/gpio.h
index 3ba8996e496c..e68a56969f36 100644
--- a/include/uapi/linux/gpio.h
+++ b/include/uapi/linux/gpio.h
@@ -490,7 +490,8 @@ struct gpioevent_request {
 /**
  * struct gpioevent_data - The actual event being pushed to userspace
  * @timestamp: best estimate of time of event occurrence, in nanoseconds
- * @id: event identifier
+ * @id: event identifier, one of %GPIOEVENT_EVENT_RISING_EDGE or
+ *  %GPIOEVENT_EVENT_FALLING_EDGE
  *
  * Note: This struct is part of ABI v1 and is deprecated.
  * Use &struct gpio_v2_line_event instead.
-- 
2.39.2