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-rw-r--r--Documentation/driver-api/gpio/drivers-on-gpio.rst6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/driver-api/gpio/drivers-on-gpio.rst b/Documentation/driver-api/gpio/drivers-on-gpio.rst
index 41ec3cc72d32..af632d764ac6 100644
--- a/Documentation/driver-api/gpio/drivers-on-gpio.rst
+++ b/Documentation/driver-api/gpio/drivers-on-gpio.rst
@@ -96,6 +96,12 @@ hardware descriptions such as device tree or ACPI:
way to pass the charging parameters from hardware descriptions such as the
device tree.
+- gpio-mux: drivers/mux/gpio.c is used for controlling a multiplexer using
+ n GPIO lines such that you can mux in 2^n different devices by activating
+ different GPIO lines. Often the GPIOs are on a SoC and the devices are
+ some SoC-external entities, such as different components on a PCB that
+ can be selectively enabled.
+
Apart from this there are special GPIO drivers in subsystems like MMC/SD to
read card detect and write protect GPIO lines, and in the TTY serial subsystem
to emulate MCTRL (modem control) signals CTS/RTS by using two GPIO lines. The