gpio: Documentation update

[sfrench/cifs-2.6.git] / Documentation / gpio / driver.txt

diff --git a/Documentation/gpio/driver.txt b/Documentation/gpio/driver.txt
index d8de1c7de85a748b266cc2329af8af31d4fbf3f6..3392a0fd4c23c817758bd94b763022ff9cf3e309 100644 (file)
--- a/Documentation/gpio/driver.txt
+++ b/Documentation/gpio/driver.txt
@@ -88,6 +88,10 @@ ending up in the pin control back-end "behind" the GPIO controller, usually
 closer to the actual pins. This way the pin controller can manage the below
 listed GPIO configurations.
 
+If a pin controller back-end is used, the GPIO controller or hardware
+description needs to provide "GPIO ranges" mapping the GPIO line offsets to pin
+numbers on the pin controller so they can properly cross-reference each other.
+
 
 GPIOs with debounce support
 ---------------------------