path: root/Documentation/gpio.txt
diff options
authorDavid Brownell <dbrownell@users.sourceforge.net>2008-10-16 05:03:16 (GMT)
committerLinus Torvalds <torvalds@linux-foundation.org>2008-10-16 18:21:40 (GMT)
commit35e8bb5175c1a6ff6253f1a2acb30bfe52a2f500 (patch)
tree88a1e9695824f88efef3340fd53f8dbe576f5852 /Documentation/gpio.txt
parent93a22f8b95756c53e80308820892119c910d2739 (diff)
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>
Diffstat (limited to 'Documentation/gpio.txt')
1 files changed, 4 insertions, 0 deletions
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 @@ signal, or (b) something wrongly believes it's safe to remove drivers
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,

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