gpiolib: request/free hooks
Add a new internal mechanism to gpiolib to support low power
operations by letting gpio_chip instances see when their GPIOs
are in use. When no GPIOs are active, chips may be able to
enter lower powered runtime states by disabling clocks and/or
power domains.
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: "Magnus Damm" <magnus.damm@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt
index 8a7c459..b1b9887 100644
--- a/Documentation/gpio.txt
+++ b/Documentation/gpio.txt
@@ -240,6 +240,10 @@
needed to manage a signal that's in active use. That is, requesting a
GPIO can serve as a kind of lock.
+Some platforms may also use knowledge about what GPIOs are active for
+power management, such as by powering down unused chip sectors and, more
+easily, gating off unused clocks.
+
These two calls are optional because not not all current Linux platforms
offer such functionality in their GPIO support; a valid implementation
could return success for all gpio_request() calls. Unlike the other calls,
