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| author | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2007-10-12 21:27:47 -0400 |
|---|---|---|
| committer | Dmitry Torokhov <dmitry.torokhov@gmail.com> | 2007-10-12 21:27:47 -0400 |
| commit | b981d8b3f5e008ff10d993be633ad00564fc22cd (patch) | |
| tree | e292dc07b22308912cf6a58354a608b9e5e8e1fd /Documentation/gpio.txt | |
| parent | b11d2127c4893a7315d1e16273bc8560049fa3ca (diff) | |
| parent | 2b9e0aae1d50e880c58d46788e5e3ebd89d75d62 (diff) | |
Merge master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6
Conflicts:
drivers/macintosh/adbhid.c
Diffstat (limited to 'Documentation/gpio.txt')
| -rw-r--r-- | Documentation/gpio.txt | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/Documentation/gpio.txt b/Documentation/gpio.txt index 36af58eba13..6bc2ba215df 100644 --- a/Documentation/gpio.txt +++ b/Documentation/gpio.txt @@ -75,6 +75,9 @@ using the include file: If you stick to this convention then it'll be easier for other developers to see what your code is doing, and help maintain it. +Note that these operations include I/O barriers on platforms which need to +use them; drivers don't need to add them explicitly. + Identifying GPIOs ----------------- @@ -145,7 +148,7 @@ pin ... that won't always match the specified output value, because of issues including wire-OR and output latencies. The get/set calls have no error returns because "invalid GPIO" should have -been reported earlier in gpio_set_direction(). However, note that not all +been reported earlier from gpio_direction_*(). However, note that not all platforms can read the value of output pins; those that can't should always return zero. Also, using these calls for GPIOs that can't safely be accessed without sleeping (see below) is an error. @@ -236,7 +239,7 @@ map between them using calls like: Those return either the corresponding number in the other namespace, or else a negative errno code if the mapping can't be done. (For example, some GPIOs can't used as IRQs.) It is an unchecked error to use a GPIO -number that hasn't been marked as an input using gpio_set_direction(), or +number that wasn't set up as an input using gpio_direction_input(), or to use an IRQ number that didn't originally come from gpio_to_irq(). These two mapping calls are expected to cost on the order of a single |