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| author | David Brownell <dbrownell@users.sourceforge.net> | 2008-10-15 22:03:16 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-10-16 11:21:40 -0700 |
| commit | 35e8bb5175c1a6ff6253f1a2acb30bfe52a2f500 (patch) | |
| tree | 88a1e9695824f88efef3340fd53f8dbe576f5852 /Documentation/gpio.txt | |
| parent | 93a22f8b95756c53e80308820892119c910d2739 (diff) | |
| download | lwn-35e8bb5175c1a6ff6253f1a2acb30bfe52a2f500.tar.gz lwn-35e8bb5175c1a6ff6253f1a2acb30bfe52a2f500.zip | |
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')
| -rw-r--r-- | Documentation/gpio.txt | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index 8a7c45956d24..b1b988701247 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, |